Toyota Diagnosis master training course

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Verifying and Reproducing the Symptoms Diagnostic Questioning

Diagnostic questioning involves asking the customer about the conditions when the symptoms occurred to reproduce those symptoms.

1. What the technician must keep in mind when perform- ing diagnostic questioning

• Not to use technical terms and speak in words unfamiliar to the customer.

• Ask the customer using examples so that the customer can easily answer.

Example

Where: Right front tire?

When: When you are driving?

What do you do: If you depress the brake, can you hear the sound?

How: A squeaking sound can be heard?

Since when: When did the symptoms begin?

2. What the technician should understand about diagnos- tic questioning

When performing diagnostic questioning, it is essential for the technician to completely understand the conditions required to reproduce the symptoms that the customer points out.

(1) What the technician has to understand

• When the symptoms are reproduced:

Confi rm the customer's requests and demands

• When the symptoms are not reproduced:

Confi rm the conditions required to reproduce the symptoms

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(2) What the technician should ask the customer for refer- enceThere is a list of questions that make it easier for the technician to troubleshoot if he has asked beforehand. But those are only for reference and the technician should not have any preconceptions or fi xed ideas.

REFERENCE:

Cases in diagnostic questioning

(See “Basic Skills” of “Fundamentals of Troubleshooting” on PDF(2 of 2) Attachment A-1,A-2)

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Verifying and Reproducing the

Symptoms Reproducing the Symptoms

The thinking method when the technician reproduces the symptoms

When the technician attempts to reproduce the symptoms that the customer points out, he has to keep in mind the following points.

• To correctly troubleshoot, it is important to create conditions and circumstances that are similar to those that exist when the symptoms occur, based on the information gathered from diagnostic questioning.

1. Confi rm the symptoms through a road test

• This test should be performed under the conditions related to when the symptoms occur, based on the information obtained through diagnostic questioning and freeze frame data of ECU.

HINT:

If possible, it is best to perform the road test with the customer.

2. Reproducing method when the vehicle is stopped

This test is performed when the vehicle is stopped in order to reproduce the symptoms whose reproductivity is low or that occur while driving.

(1) Check the diagnosis code When a malfunction code is output

If the malfunction code is displayed, focus on the system relevant to that code to reproduce the symptoms using the reproduction method.

When a normal code is output

If the code is normal, focus on the actuator system that the diagnosis did not detect and reproduce the symptoms using the reproduction method.

(2) Reproduction method

(See “Reproduction method” of “Troubleshooting” in this chapter)

Malfunction Judgement Judge Whether the Symptoms are Malfunction or Not

When the customer complains, it is important to determine whether the cause comes from the vehicle, the customer's usage or both.

It is also necessary to judge the customer's vehicle performance whether the customer's requirement is equal or not by comparing it to another vehicle of the same model. If the performance level is equal, it is nearly impossible to remove the cause of the complaint by repair, so the technician should judge that the complaint is not a malfunction symptom but the customer's expectation, and deal with it from another perspec- tive. If the level is considerably worse than that of another vehicle of the same model, the technician should judge that the complaint is a malfunction and perform troubleshooting.

When the technician compares the customer's vehicle with another vehicle of the same model.

• The driving conditions should be the same.

• If the technician cannot judge whether there is a malfunction or not, he should consult with several colleagues, evaluate and make a decision.

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Troubleshooting Outline

With regards to the inspection for troubleshooting, besides the inspection method you have learned, a method to identify the malfunction location is needed.

When you troubleshoot, combine several inspections to perform an estimation to fi nd the cause.

• Reproduction method

• Diagnostic inspection

• ECU data inspection

• Engine rotation resistance inspection

• Engine starting condition inspection

• Ignition, glow system inspection

• Fuel system inspection

• Compression system inspection

• Power balance inspection

• A/F inspection

• Oil loss via the piston rings/valve guides inspection

• Exhaust condition inspection

• Terminal contact pressure inspection

Troubleshooting Reproduction Method

The technician should perform the reproduction using a tech- nique based on the conditions that result in the symptoms that the customer points out. Depending on the conditions in which the symptoms occur, the reproduction method should be performed by combining several techniques.

1. Apply vibration 2. Apply heat and/or cold 3. Apply water

4. Apply electrical load HINT:

During the procedure, if the connector is unintentionally disconnected or connected, the contact condition changes and the symptoms may not be reproduced. Until the symptoms are confi rmed by the reproduction, do not attempt to disconnect and connect the connector. The connector should not be disconnected and connected until the symptoms have been confi rmed and the technician can perform troubleshooting.

If the symptoms are reproduced when the technician vibrates the wire harnesses, or heats or cools the parts, the cause can be judged to be there. In this case, perform the reproduction method while measuring the voltage to determine whether or not the malfunction occurs at the specifi ed voltage in order to determine the malfunction location.

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Troubleshooting Reproduction Method

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1. Apply vibration

Similar to when the vehicle vibrates to create a situation where the engine is inclined or the wire harness is pulled, vibrate the sensors and wire harnesses in order to reproduce the malfunction including poor contact.

Inspection method

• Parts and sensors

Lightly tap the parts and sensors with a fi nger in order to check whether or not the malfunction occurs.

NOTICE:

For relays, the contacts will open when there is a strong impact. Therefore even if they are normal, a malfunction may occur.

• Wire harness and connector

Lightly swing the wire harnesses up and down or right and left to check for a malfunction.

For the wire harness in particular, focus inspection on the base of the connectors, the fulcrum of the vibration and the through part of the body.

NOTICE:

If the terminal is disconnected within the connector, carelessly pushing in the wire harness will connect the terminal, preventing the malfunction from being reproduced.

• Engine vibration

Malfunction of the wire harnesses in the engine compartment may occur when the engine is tilting due to torque reactive force. In an A/T vehicle, stalling an engine in the D or R range may reproduce the symptoms.

2. Apply heat or cold

To create a condition where parts expand or contract due to a temperature change, heat and cool the parts in order to reproduce poor contact or a short circuit.

Apply heat or cold to parts using a hair drier, spot air conditioner, refrigerator, and so on to check whether the malfunction occurs or not.

NOTICE:

• Heat to a temperature where the technician can still touch by hand (approximately 60 degrees centigrade (140 degrees Fahrenheit) or less)

• Do not directly heat or cool the electronic parts by opening the lid of the ECU, etc.

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Troubleshooting Reproduction Method 3. Apply water

To create the conditions where water enters or condensation is produced in the connector, apply water to the vehicle in order to reproduce the malfunction, including poor contact or a short circuit.

Apply water to the vehicle in order to check whether the malfunction occurs or not.

NOTICE:

• Do not directly apply water to the engine compartment, but spray the front of the radiator to indirectly apply moisture to the vehicle.

• Do not directly apply water to the electronic parts.

HINT:

If rain leaks into the cabin, water may enter the ECU or connector through the wire harness. Therefore, this should be checked, especially if the vehicle has a history of leaks.

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4. Apply electrical load

To create the conditions where the battery voltage drops or fl uctuations occur, apply a large electrical load to reproduce the malfunction, including a voltage drop or fl uctuation.

Turn on all electrical devices, including heater blower, head- lamp, rear window defogger to inspect for the malfunction.

Troubleshooting Diagnostic Inspection

Outline

To effi ciently proceed with troubleshooting, use diagnostic codes in order to identify the malfunctioning area.

The following are judged by identifying the codes.

• When DTC is displayed

The sensors, actuators, wiring and ECUs in the systems indi- cated by the malfunction codes may have a malfunction.

• When normal DTC is displayed

Systems that have a diagnostic function can be judged normal.

Therefore, the malfunction may be in the systems that have no diagnostic function so proceed to this inspection.

HINT:

The systems that have no diagnostic function include the ignition secondary system, fuel system, etc.

• When No DTC is displayed

The ECUs themselves do not operate or the power source system of the ECU has a malfunction.

HINT:

Check mode

In normal mode, if a malfunction only momentarily occurs, it cannot be detected because it does not satisfy the diagnostic conditions. By switching into check mode, malfunction which occur momentarily, such as poor contact, can be detected.

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Troubleshooting Diagnostic Inspection Purpose of inspection

Check whether the identifi ed diagnostic code accords with the actual malfunction symptoms.

The malfunction systems that the code indicates may not accord with the system that actually indicates the malfunction.

(1) Inspect the diagnostic code and freeze frame data and record them.

(2) Clear the diagnostic code and reproduce the malfunction symptoms based on diagnostic questioning.

HINT:

To judge whether the displayed code when the vehicle was brought in is caused by a current malfunction or past malfunction, clear the displayed code once and then perform the reproduction test.

(3) Identify the diagnostic code again and judge whether the code is related to the malfunction or not.

Criteria

• If the same code is displayed, it can be judged that the malfunction currently occurs in the system that the code indicates.

• If a code that is not related to the malfunction is displayed, or a normal code is displayed, the current malfunction is caused by something else. Therefore, perform troubleshooting appropriate for the malfunction symptoms.

Troubleshooting Data of ECU Inspection

Purpose of inspection

Inspect the condition of the ECU (input signal, output signal) when the malfunction occurs and determine the cause by checking the data of ECU.

• Freeze frame data

Freeze frame data is data of ECU when the diagnostic codes are recorded.

Malfunctions are judged depending on whether the malfunction signal system is an open circuit or short circuit, based on the type of freeze frame data.

Example:

When the codes from the water temperature signal system are detected:

Check the freeze frame data on the water temperature signal. If the temperature is -40 degrees centigrade, the malfunction can be judged to be an open circuit. If it is 200 degrees centigrade or more, the malfunction can be judged to be a short circuit.

HINT:

• Freeze frame data is deleted when the diagnostic codes are cleared or the modes are switched. Therefore, check freeze frame data immediately after checking diagnostic codes.

• As for diagnosis detection, there is time lag between malfunction occurrence and detection.

Therefore, it is not the data at the time of malfunction occurrence but the data after the time lag is stored in memory as a freeze frame data.

• By referring to the freeze frame data, it is possible to estimate to some degree, the running conditions at the time of the malfunction.

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• ECU data

ECU conditions can be checked by using ECU data even if the diagnostic codes are not identifi ed. The auto trigger function makes it possible to automatically record

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Troubleshooting Engine Rotation Resistance Inspection Purpose of inspection

This inspection determines whether the cause of the engine not correctly cranking is in the starting system or in the engine proper.

(1) Remove all spark plugs/glow plugs

(2) Place the offset wrench on the crankshaft pulley bolt and turn it to measure the rotating resistance.

Criteria

Since there is no standard value for engine rotation resistance, compare it with a normal engine.

• When the engine rotation resistance is extremely large

Remove all drive belts and recheck the engine rotation resistance.

Criteria

• Rotation resistance is large:

malfunction in the engine

• Rotation resistance is small:

malfunction in the auxiliary components HINT:

Perform the inspection under the conditions in which the malfunctions occurred such as when it is cold or hot.

Troubleshooting Engine Starting Condition Inspection Purpose of inspection

The cause of malfunctions related to engine starting differs depending on whether the initial combustion occurs or not, or whether starting takes too much time or not.

Therefore, inspect the engine starting condition to determine the cause of the malfunction.

Crank the engine to check the engine starting condition.

Criteria (gasoline engine)

1. No initial combustion, does not start

One of the three engine elements (that affect engine performance) may have caused a malfunction.

2. Takes time to start

Based on the fact that the engine can start, the three engine elements can be judged as normal. Therefore, the malfunction may be caused by the air fuel ratio when starting.

3. Initial combustion occurs but immediately stalls

The ignition system and the compression system can be judged as normal. Also, the fuel system can be judged as normal only when the engine starts. Therefore, the malfunction may be caused by a drop in fuel pressure, ISCV (Idle Speed Con- trol Valve), etc.

HINT:

If the malfunction is caused by the ISCV opening, starting while depressing the accelerator pedal maintains the amount of intake air and the engine runs without stalling.

Criteria (diesel engine)

1. No initial combustion, does not start Takes a long time to start

The malfunction may be caused by one of the three engine elements.

HINT:

In the fuel system, a malfunction of the injection timing will not cause engine starting to become diffi cult.

2. Initial combustion occurs but immediately stalls

The glow system and compression system can be judged as normal. The fuel system can be judged to be normal only when the engine starts. Therefore, the malfunction may be caused by the injection pump operation when the engine is idle.

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Troubleshooting Ignition and Glow System Inspection Inspection method (gasoline engine)

Remove the spark plug and crank the engine to check for a spark at the tip of the plug and the spark's strength.

NOTICE:

Before inspecting, remove the injector connector so that fuel does not inject.

Criteria

• A spark appears at the tip of the spark plug, and there is no electrical leak.

• To judge the strength of the spark, compare with a spark plug from a normal engine and if a large difference is not found, it should be normal.

HINT:

Pay attention to the strength of the spark in normal engines on a daily basis.

Inspection method (diesel engines) Inspect the following in the glow system.

• Lighting time of the glow indicator lamp

• Pre-heat function

• After-glow function HINT:

For this procedure, refer to the Repair Manual.

Troubleshooting Fuel System Inspection

Inspection method (gasoline engines) Inspect the following when cranking the engine.

(1) Pinch the engine compartment fuel hose with your fi ngers and check whether or not fuel pressure is applied.

(2) Check the sound that the injector is making.

Criteria

• Fuel pressure is applied to the fuel hose, then tension increases and the hose pulsates.

When there is no fuel pressure:

A malfunction may exist in the fuel pump system

• Injector is making a sound

When the injector is not making a sound:

Exchange the connector with one from the next cylinder. If a sound can be heard, the injector can be judged as normal.

The malfunction can be found between the ECU and the wire harness.

Inspection method (diesel engines)

When inspecting a diesel engine's fuel system, separate the system into its compartment segments and check into which part the fuel comes.

(1) Is the fuel coming to the injection nozzle?

Loosen the union at the injection nozzle when cranking the engine to check the fuel injection condition.

NOTICE:

Cover the injection nozzle with a cloth so that the fuel does not spatter.

Criteria

When fuel spurts intermittently from the loosened part while cranking, it is normal.

(2) Is the fuel in the injection pump?

Check the sound of the fuel cut solenoid.

Criteria

If a sound can be heard when the ignition switch is ON and OFF, it is normal.

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Troubleshooting Compression System Inspection Inspection method

Using a compression gauge, measure the compression pressure.

Criteria

The standard value differs depending on the engine model, therefore refer to the Repair Manual.

When compression pressure is low

Fill the cylinder with oil and check the change in the compression pressure.

• Does not change: cylinder head side

• Changes: cylinder block side HINT:

As a quick inspection for compression pressure, the following methods are avail- able.

• Check whether or not the compressed air comes out of the plug hole when cranking.• Check whether or not the cam shaft pulley rotates when cranking by looking through the service hole of the timing belt cover.

・A lack of compression due to a cut in the timing belt can be found by listening to the sound made when cranking.

Troubleshooting Cylinder Power Balance Inspection Purpose of inspection

By confi rming the change in the engine speed when the combustion of each cylinder is stopped in turn for power balance inspection, judge whether or not the malfunction affects the specifi c cylinder or all the cylinders.

Inspection method (gasoline engines)

Remove the injector connectors one by one while the engine revolves to check the engine speed and how the vibration changes.

Criteria

The engine speed does not decrease, or if there is a cylinder that has a small change, the malfunction is in the cylinder.

HINT:

When judgement is diffi cult, slightly increasing the engine speed will make it easier.

Inspection method (diesel engines)

To check the engine speed and vibration, control the amount of fuel injected into the cylinders by slowly loosening and tightening the union nut of the injection nozzle, check the engine speed and vibration.

Criteria

The engine speed does not decrease, or if there is a cylinder that has almost no change, the malfunction is in the cylinder.

HINT:

• If one cylinder injects more than other cylinders or if there is more power than other cylinders, the engine revolves unstably.

In such a case, loosening the union nut to release the fuel may stabilize engine revolution.

• With a common rail diesel engine

Using an intelligent tester, stop the fuel injection in each cylinder to perform the inspection.

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Troubleshooting Air Fuel Ratio (A/F) Inspection Purpose of inspection

To determine whether the malfunction is a rich or a lean air fuel mixture.

Criteria

Using an intelligent tester, check the voltage of the O2 sensor or short term fuel trim.

The factors that change the A/F balance (1) When the A/F ratio is small (rich)

Consider the factors that cause the fuel system injection amount to increase, or inject continuously

• Sensor range/performance problem

• Poor contact with the ground of the sensor system

• Injector dribbling etc.

(2) When the A/F ratio is great (lean)

Consider the factors that cause the fuel system injection amount to decrease.

• Sensor range/performance problem

• Fuel pressure is low

• Poor contact with the ground of the injector system

• O2 sensor system malfunction (the signal shows the mixture is rich)

• Absorption of fuel due to carbon accumulation etc.

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Troubleshooting Oil Loss Via the Piston Ring/the Valve Guides Inspection Purpose of inspection

When burning oil causes white smoke to be seen in the exhaust gas, changing the engine rpm to change the volume of white smoke allows you to judge whether oil loss via the piston rings or oil loss via the valve guides exists. As well, disassemble the engine and judge the condition of the accumulated carbon.

Exhaust gas inspection

• Judge if there is oil loss via the piston rings

After warming up the engine, race it at approximately 2000 to 3000 rpm to check the state of the exhaust gas

Criteria

• White smoke increases when the engine is raced

• White smoke increases when rpm rises

• Judge if there is oil loss via the valve guides

After warming up the engine, let it idle for approximately 5 minutes then race it to check the state of the exhaust gas.

Criteria

White smoke will discharge for approximately 30 to 60 seconds at the start of racing, but the amount will gradually reduce.

Why the cause of white smoke can be determined by oil loss via the piston rings (1) The temperature in the combustion chamber is low when the engine is idle, therefore even if oil loss from the piston rings occurs, the oil does not burn. There- fore, the volume of white smoke is small.

(2) When engine speed increases, the temperature in the combustion chamber rises as does the amount of oil supplied to the cylinders. As a result, the amount of white smoke discharged increases.

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Troubleshooting Oil Loss Via the Piston Ring/the Valve Guides Inspection

Why the cause of white smoke can be determined by oil loss via the valve guides (1) The negative pressure of the intake manifold is high when the engine is idle, so oil is sucked into the combustion chamber from the valve stem. However, the temperature in the combustion chamber is low, so the oil attaches to the carbon, etc.

and accumulates on the valve or combustion chamber, decreasing the amount of white smoke.

(2) When racing the engine from the above state (1), the temperature of the com- bustion chamber increases, instantly burning the accumulated oil, causing a great deal of white smoke to discharge. When the oil is completely burnt, the amount of white smoke decreases.

(3) If the engine is continuously raced, the temperature in the combustion cham- ber rises, so even if the oil is sucked in, it is burnt before accumulating, therefore decreasing the amount of white smoke.

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Engine disassembly inspection

• With oil loss via the piston rings

A lot of carbon attaches to the outer circumference at the top of the piston.

• With oil loss via the valve guides

A lot of carbon attaches to the intake valve face, at the top of the piston, or to the exhaust valve stem. In addition, oil can also attach to these parts, making them wet.

HINT:

When oil loss via the valve guides is discovered, remove the intake and exhaust valves and inspect the conditions at the face and stem.

Troubleshooting Exhaust Condition Inspection

Purpose of inspection

Inspect the diesel engine's combustion condition based on the discharged smoke.

• With white smoke

White smoke is caused by combustion at a comparatively low temperature and is discharged when the injected fuel is not burnt.

The cause of white smoke may be conditions where the fuel injection timing is retarded, or the after glow does not operate when it is cold, etc. For these reasons, checking the conditions when white smoke is discharged can determine the cause of the malfunction.

(1) White smoke is discharged regardless of the condition

• Internal malfunction of the injection pump

• Compression pressure is low

• Fuel cetane number is low

(2) White smoke is discharged when it is coldetc.

Operational malfunction of the after glow HINT:

White smoke is sometimes discharged because engine oil or water enters the combustion chamber. In this case, checking the smell of the discharged gas will make it possible to judge whether engine oil or water has caused a fuel ignition failure.

Check the smell by fanning the smoke by hand so as not to directly inhale it.

• With black smoke

When injected fuel particles are exposed to a high temperature and there is a lack of oxygen, the fuel becomes soot. Black smoke is this soot. Only the outside of the fuel drop is burnt, not the center.

The following can be considered causes of black smoke: a large amount of fuel is injected, a small amount of air is taken in, the injection timing of the fuel is fast, atomization is poor, etc.

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Troubleshooting Terminal Contact Pressure Inspection Purpose of inspection

When a malfunction such as poor contact occurs momentarily, inspect the contact pressure to determine where the malfunction area is.

(1) Disconnect the connector

(2) Visually check for rust or foreign matter on the connector terminals.

(3) Check for looseness or damage on the staked position of the terminal. Lightly pull the wire harness and check that they are not disconnected.

(4) Turn up the engaging surface of the female connector and insert a male terminal unit into each one of the female terminals, one at a time.

HINT:

Prepare a male terminal from an identical model connector by cutting one repair wire, and use that when testing the female terminal.

(5) Hold the female connector by hand, wiggle it to the right and left and check whether the inspected terminal sinks due to its weight.

Criteria

• When the constriction of the male terminal can be seen, it has contact pressure and is judged to be normal.

• When the constriction of the male terminal hides in the connector, it has no contact pressure, so replace the terminals or connectors.

Recurrence Prevention The Thinking of Recurrence Prevention

The malfunction has not been completely resolved if the problem recurs immediately after repair. Therefore, it is important to pursue the true cause of the problem so that it will not recur.

Important points for preventing recurrence

• Is it an independent occurrence, or was it caused by another part?

When starting the engine is diffi cult due to incomplete ignition by the smoldering spark plug, even if the malfunction is resolved by replacing or cleaning the plug, if the cause is not inspected, the malfunction could recur.

• Is it due to the life of the part?

Parts will degrade after a long period of use, causing heat resistance and durabil- ity to worsen or become worn. As a result, they will not be able to maintain their original performance. Therefore, it is important to help the customer understand the concept that a part has a predetermined life.

• Is it due to improper maintenance?

Even if the amount of oil used increases due to the engine malfunction, the true cause of the engine malfunction might be engine wear caused by oil degradation due to insuffi cient oil maintenance. Therefore, it is important to help the customer understand the importance of maintenance.

• Is it due to improper handling, operation or usage conditions?

Even when usage or road conditions are the same, a difference in acceleration or shifting may cause malfunctions. Check for improper handling including rally driving, over-load, and toeing through diagnostic questioning.

• Is the customer's expected performance too high?

If there are no malfunctions and the performance of the customer's vehicle is no worse than others of the same model, it is important to explain to the customer the function/performance of the vehicle based on diagnostic questioning to help him understand.

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Exercises

Use the Exercises to check your level of understanding for the material in this Chapter. After answering each Exercise, you can use the reference button to check the pages related to the current question. When you get a incorrect answer, please return to the text to review the material and find the correct answer. When all questions have been answered correctly, you can go to the next Chapter.

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AnswersAll Correct

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Mark each of the following statements True or False.

No. Correct

Answers

1. nmlkj nmlkj

2. _n_m_l_k_j _n_m_l_k_j

4. nmlkj nmlkj

When performing diagnostic questioning, it is important not to have preconceptions or fixed ideas.

When performing diagnostic questioning, confirm only the customer's requests and demands.

During the road test, drive under all the conditions, which the customer habitually uses.

When symptoms that the customer points out do not occur, reproduce them using the reproduction method.

True False True False

True False

5. To reproduce the symptoms, confirm the when, in what occasion, how, frequency, _n_m_l_k_j _n_m_l_k_j

etc. through diagnostic questioning. True False

True False

Question True or False

Question-1

No. Correct

Answers

1. nmlkj nmlkj

4. nmlkj nmlkj

Engine rotation resistance inspection can determine whether the cause of the engine not correctly cranking is in the starting system or in engine proper.

When inspecting the engine starting condition, if there is no initial combustion nor does it start, the malfunction is in one of the three engine elements.

When compression pressure is low in compression system inspection, whether the malfunction is on the cylinder head side or cylinder block side can be estimated by checking whether compressed air is released from the plug hole when cranking.

When inspecting cylinder power balance, if it is difficult to check the change of the engine speed when stopping the combustion in each cylinder, decreasing the engine speed makes it easier to judge.

True False

5. When inspecting oil loss via the piston rings and via the valve guides, if racing _n_m_l_k_j _n_m_l_k_j the engine after warming up discharges a large amount of white smoke and rising

engine speed increases the amount of discharged white smoke, it can be judged to be oil loss via the piston rings.

Question-2

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No. Correct

Answers

1. nmlkj nmlkj

4. nmlkj nmlkj

When performing a diesel engine's exhaust condition inspection, if white smoke is discharged while it is cold, an operation malfunction of the after glow can be considered.

When inspecting the air fuel ratio, only when the air fuel mixture is rich, can you estimate the malfunction location.

When inspecting a diesel engine's fuel system, separate the system into its compartment segments and check into which part the fuel comes.

When inspecting an EFI gasoline engine's fuel system, if the injector's sound cannot be heard, exchange the connector with one on the next cylinder. If the sound cannot be heard, the malfunction can be judged to be in the electrical system of the injector.

True False

5. When a malfunction, such as poor contact occurs momentarily, after estimating _n_m_l_k_j _n_m_l_k_j the malfunction area using the reproduction method, determine the malfunction

area through the terminal contact pressure inspection.

Question-3

No. Correct

Answers

1. nmlkj nmlkj

4. nmlkj nmlkj

Diagnostic questioning is asking the customer about the conditions of the malfunctioning components.

When reproducing the symptoms that the customer points out, it is important to create conditions and circumstances that are similar to those that exist when the symptoms occur.

It is important to determine whether the cause is on the vehicle side or the customer's usage.

When troubleshooting, if only using the reproduction method to determine the malfunction area, it is not necessary to perform the basic inspection such as ignition timing, idle speed, etc.

True False

5. After eliminating the malfunction, it is important to pursue the true cause of the _n_m_l_k_j _n_m_l_k_j

problem so that it will not recur. True False

True False

Question-4

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In the case of engine stall or hesitation

Diagnostic questions

- - Customer's request

-

- - Based on the date and time, weather

and temperature at that time can be estimated.

- - Based on the distance and time to the

place where the malfunction occurs, the engine's warm-up condition can be estimated.

- Based on the geography, engine load and engine speed can be ' estimated.

- - Customer's habitual operation condition

- Whether during brake operation can be estimated

- Deceleration condition - The vehicle condition when the - The speed at which deceleration malfunction occurs can be estimated.

starts -

- Whether at starting acceleration - How is the acceleration pedal

depressed

- How is the accelerator opening - Which is the gear position when

the symptom occurs

- Whether at overtaking acceleration - Initial speed? last speed

- A/C switch ON/OFF condition

Others - Frequency

In the case of hesitation

Concrete questioning

The place

How

What do the symptoms feel like The relation to the other malfunctions When the symptom occurs

Symptom

The place where the malfunction frequently occurs

In the case of engine stall

Understandable information

When, the occasion

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In the case of insufficient power

Diagnostic questioning

- Poor acceleration - Poor uphill performance - Comparison with other model - Timing

- Period of time - Weather - Frequency

The place - The place where the customer specially feels insufficiency of power - How is the accelerator pedal depressed

- How is the accelerator opening - Initial speed

- How is the accelerator pedal depressed - Last speed

- How is the acceleration pedal depressed - Engine speed

- Driving speed

- Gear position of the transmission - Vehicle condition

- A/C switch ON/OFF condition - Type of fuel

Which power is insufficient

Since when, the occasion

Which type of driving

Others

Concrete questioning

Starting acceleration

Heavy load is applied Overtaking acceleration

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Fundamentals of Troubleshooting How to Approach Troubleshooting

The most important points for troubleshooting

• Correctly identify the symptoms of the malfunction.

When troubleshooting, it is important to correctly identify the symptoms that the customer points out.

• Work effi ciently to determine the estimated cause in order to fi nd the true cause.

To correctly and promptly perform troubleshooting, systematic work is required.

Estimation must be backed up by logic and facts

When estimating the cause, a technician must not rely on his sixth sense without any logical back-up.

Asking the question "why" is of great importance. When a technician makes an esti- mations about the cause, he must check whether facts that support this estimation exist or not.

To troubleshoot the true cause, the technician must adopt a habit of following the cause-and-effect relationship of each item by observing the following cycle: estimate and verify, estimate and verify.

Fundamentals of Troubleshooting Troubleshooting Procedure

The troubleshooting procedure consists mainly of fi ve stages.

When a technician troubleshoots, and does not follow the necessary procedure, the malfunction could become complicated and fi nally the technician may perform irrelevant repair procedure due to the wrong estimation.

To prevent this, he should understand the fi ve stages accurately when troubleshooting.

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Stage 1:

Verifying and reproducing the symptom

Verifying and reproducing the symptoms is the fi rst step in troubleshooting. The most important element in troubleshooting is to correctly observe the factual malfunction (symptoms) that the customer points out and make an appropriate judgement without any preconceptions.

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Fundamentals of Troubleshooting Troubleshooting Procedure What is diagnostic questioning?

To reproduce the symptoms, ask the customer about the conditions under which the symptoms occur.

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Stage 2:

Determining whether or not it is a malfunction

When a customer makes a complaint, there are various cases.

Not all of the symptoms are related to malfunctions but could be characteristics inherent to that vehicle. If a technician repairs a vehicle that has no malfunction, he will not only be wasting valuable wasting time, but will lose the customer's trust.

What is a malfunction?

An abnormal condition that occurs in a certain portion of the equipment, causing defective function.

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Stage 3:

Estimating the cause of the malfunction

Estimating the cause of the malfunction should be done systematically based on the malfunction symptom that the technician has confi rmed.

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Fundamentals of Troubleshooting Troubleshooting Procedure

To accurately estimate the cause of the malfunction

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Stage 4:

Inspecting the suspected area and fi nding the cause Troubleshooting is a step-by-step repetitive process for approaching the true cause of a malfunction based on facts (data) obtained through verifi cation (inspection).

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Important points for inspection

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Fundamentals of Troubleshooting Troubleshooting Procedure Stage 5:

Recurrence prevention

Repairs are completed not just when the malfunction is eliminated, but when the fear of recurrence has also been removed.

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Important points for preventing recurrence

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Exercises

Use the Exercises to check your level of understanding for the material in this Chapter. After answering each Exercise, you can use the reference button to check the pages related to the current question. When you get a incorrect answer, please return to the text to review the material and find the correct answer. When all questions have been answered correctly, you can go to the next Chapter.

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No. Correct

Answers

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Diagnostic questioning is asking the customer about the conditions under which the malfunction occurred in order to reproduce the symptom.

A malfunction is a symptom that a customer points out.

As for estimation of the malfunction cause, referring to a lot of information will increase the estimatable cause, so obtain only a necessary information.

When inspecting, use a tester as much as possible.

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5. Complete repair is not only eliminating the malfunction symptoms but removing _n_m_l_k_j _n_m_l_k_j

the fear that the malfunction could recur. True False

True False

Question-1

Which one of the following statements about how to approach troubleshooting is True?

1.

2. It is important for a technician to rely on his sixth sense in order to prompt repairs.

3. Inspection of all the parts related to the malfunction can be repaired quickly.

4. If the malfunction is eliminated, it is not necessary to seek its true cause of the malfunction.

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At first, correctly identify the malfunction symptoms.

Question-2

Question-3

Which one of the following statements about troubleshooting is True?

1.

2. To correctly and promptly perform troubleshooting, it is necessary to systematically inspect based on the five stages.

3. To seek the true cause of the malfunction, it is important to securely inspect all the components one by one.

4. To promptly perform repair, inspect all of the suspected areas without following the required procedures.

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When troubleshooting, it is not the symptoms that the customer points out that are important, rather the symptoms that the technician himself confirms.

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Increased Fuel Consumption Outline

Increased fuel consumption frequently is a result of the vehicle usage and road conditions rather than vehicle malfunction. Therefore, it is important to accurately understand the customer's habitual usage and required level. In this chapter, the items regarding the estimated causes of increased fuel consumption are explained.

• Since when?

Understand the relationship between engine warm-up and A/C usage, the change of the vehicle condition and the malfunction.

• Compared to what?

Find the difference between the target vehicle that the customer compares and the customer's vehicle and troubleshoot the cause of the increased fuel consumption.

• How is it used?

Troubleshoot the cause of the increased fuel consumption based on the customer's usage.

• How is it measured?

Troubleshoot the cause of the customer's measurement error.

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Increased Fuel Consumption Since When?

1. Seasonal variation of fuel consumption

When the air conditioner is used in summer, fuel consumption increases. The degree of increase depends on the air conditioner load which is affected by the temperature and moisture. In winter, the fuel consumption also increases, because fast idling is performed for longer than the usual in order to warm up the engine.

2. Fuel consumption change over time

Knocking occurs because carbon in the combustion chamber accumulates for a long period of time. Knock control retards the ignition timing increasing fuel consumption. If the ignition timing retards by fi ve degrees, the fuel consumption increases by approximately 6%. When a brand new vehicle runs approximately 5,000 to 10,000 km, the fuel consumption decreases by 5 to 10 %. This is because the friction to the engine, drive train, tires, etc. is reduced.

3. Rapid change in the fuel consumption

"Fuel consumption has increased a lot compared to last year," "Suddenly, the fuel consumption has increased, " a sort of malfunction may have occurred to the vehicle.

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Increased Fuel Consumption Compared to What?

1. Difference in the engine

• In general, fuel consumption is greater when the engine displacement is larger.

The main cause being that friction increases as the engine is larger and the vehicle weight is heavier.

• The fuel consumption in the normally used range is almost the same despite of the characteristics of the engine; an engine that has great torque at a low speed and that has great at a high speed. The gear ratio of the engine that has great torque at a low speed is set smaller, however, in this case, the fuel consumption can be said to be decreased.

• In an engine equipped with a turbocharger/supercharger, the driver frequently depresses the accelerator pedal more than is necessary, because of its slow reaction when moment of starting and accelerating. As a result, the turbocharger/

supercharger functions, starting the acceleration to be greater than is necessary and the fuel consumption increases.

HINT:

Minimum fuel consumption rate

The minimum fuel consumption rate shown by the engine performance curve is when the throttle valve is fully opened and it is not always equal to the fuel consumption in the normally used range.

Increase in displacement

Characteristics of torque

Turbocharger/supercharger

2. Vehicle weight difference

As the vehicle weight is greater, fuel consumption increases. The increase in vehicle weight does not greatly affect the fuel consumption while driving at a con- stant speed on a fl at road. But, when repetitively starting, accelerating and climbing uphill, the vehicle weight largely affects the fuel consumption.

3. Difference in style (aerodynamics)

The air resistance increases against the square of the vehicle speed. Therefore, in low-speed driving, the air resistance does not affect the fuel consumption, but in high-speed driving, it largely affects the fuel consumption.

HINT:

The air resistance is in proportion to the multiplication of the Cd value of the frontal projected area. In other words, even if the Cd value is small, the frontal projected area is large, so the air resistance becomes large. Therefore, even if the Cd value in a large vehicle is small, the air resistance is not always small. In short, it cannot be said that the fuel consumption will decrease.

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