In this group, the electronic control system is described in the following categories:
• Electronic Control System Terminology
• Electronic Control System Operation
• Monitoring Engine Parameters
• Electronic Control System Overview - Tier 1
• Electronic Control System Overview - Tier 2
• Measuring Temperature
– Engine Coolant Temperature (ECT) Sensor – Manifold Air Temperature (MAT) Sensor
• Measuring Pressure – Fuel Pressure Sensor – Oil Pressure Sensor
• Measuring Throttle Position – Analog Throttle
– CAN Throttle – Dual State Throttle – Excavator Throttle – Multi-state Throttle
– Pulse-Width Modulated (PWM) Throttle – Ramp Throttle
– Tri-state Throttle
• Measuring Engine Speed – Crankshaft Position Sensor – Pump Position Sensor
• Electronic Transfer Pump
• Water in Fuel (WIF) Sensor
• Pump Control Unit
• Engine Control Unit (ECU)
• Controlled Area Network (CAN)
• Intake Air Heater Operation
• Cruise Control Operation
• Engine Protection
• Derate Programs
• Multiple Torque Curves Selection
• Governor Droop Mode Selection
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Electronic Control System Terminology
Actuator A device controlled by the (ECU) to perform a certain function.
Analog Signal which has a continuous range of possible voltages. Usually 0 to 5 volt or 0 to 12 volt signals.
Boost Air charge pressure in the intake manifold.
CAN Controller Area Network. The electronic pathway network on vehicles that allows communication between controllers.
DTC Diagnostic Trouble Code. A code which is stored in the ECU’s memory when the ECU detects a problem in the electronic control system.
DST Diagnostic Scan Tool. This is a diagnostic software that is used to read engine parameters, check DTCs, and run special tests. The DST consists of an Windows (’95, ’98, 2000) or NT compatible computer and a hardware kit available from John Deere Distribution Service Center (DSC): JDIS121 - ECU Communication Hardware Kit. The software is available to download from your John Deere home page.
Digital A signal which consists of only two-volt levels — usually 0 volts and +5 volts.
ECT Engine Coolant Temperature (sensor). Measures the temperature of the engine coolant. See MEASURING TEMPERATURE later in this Group for details.
ECU Engine Control Unit. The computer which controls the fuel, air, and ignition systems on the engine. See ENGINE CONTROL UNIT (ECU) later in this Group for details.
FMI Failure Mode Identifier. The second part of a two-part code that identifies control system trouble codes according to the SAE J1939 standard. The FMI identifies the type of failure that has occurred. The first half of the code is the Suspect Parameter Number (SPN).
J1587/J1708 The Society of Automotive Engineers (SAE) standard for the electronic components of heavy duty vehicles. J1587
is the software standard. J1708 is the hardware standard.
MAT Manifold Air Temperature (sensor). Measures the temperature of the air in the intake manifold. See MEASURING TEMPERATURE later in this Group for details.
PDM Parallel Data Module. Device used as part of the DST that allows communication with the ECU.
PROM Programmable, Read-Only Memory. The computer chip which contains the calibration information for the engine control system. See ENGINE CONTROL UNIT (ECU) later in this Group for details.
PSG Pump Control Unit. The controller for the Bosch VP44 rotary injection pump. This is located on top of the injection pump. The acronym PSG derives from the German word Pumpensteuergerat.
PWM Pulse Width Modulation. A digital signal (not analog) which consists of a pulse generated at a fixed frequency. When an actuator is controlled by a PWM signal, the on time of the signal is increased or decreased (modulated) to increase or decrease the output of the actuator.
RAM Random Access Memory. The portion of computer memory within the ECU which changes as the engine is running and is stored while the engine is off. See ENGINE CONTROL UNIT (ECU) later in this Group for details.
SAE Society of Automotive Engineers. Working with society to promote vehicle safety and maintenance and energy resource conservation.
Sensor Device used by the ECU to monitor various engine parameters.
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SPN Suspect Parameter Number. The first half of a two-part code that identifies control system fault codes according to the SAE J1939 Standard. The SPN identifies the system or component that has the failure. The second half of the code is the Failure Mode Identifier (FMI).
VBAT Battery voltage or unswitched voltage.
VSW Switched voltage
Electronic Control System Operation
Engine Starting Mode
When the key is turned to the “ON” position, a switched power voltage is sent to the Electronic Control Unit (ECU). This energizes the ECU and allows it to “boot-up” and ready itself for engine start.
NOTE: If a wiring problem prevents the key ON signal from getting to the ECU, the engine will not start.
As soon as the ECU receives an input from the crankshaft position sensor that the engine is cranking, it will determine using the pump position sensor input when cylinder number 1 is coming to top-dead-center (TDC) at the end of the compression stroke. It will then start injecting fuel when the next cylinder in the firing order (cylinder number 5) is at the correct position before TDC at the end of its compression stroke. To provide cold temperature enrichment, the amount of fuel injected is based on the temperature measured by
the Engine Coolant Temperature (ECT) sensor. At this point, the engine will start and the ECU will go into the running mode.
Engine Running Mode
In the running mode, both the pump and crankshaft position sensors allow the ECU to precisely determine piston position in relation to top-dead-center so that the ECU can inform the pump control unit (PSG) of the operating conditions of the engine. Given the
information from the ECU and the sensors internal to the pump, the PSG controls fuel delivery by energizing and de-energizing the high pressure solenoid valve. When the PSG energizes the high pressure solenoid valve, the valve needle closes and injection begins. When the correct amount of fuel has been injected, the PSG de-energizes the high pressure solenoid valve, causing the valve needle to open, and fuel injection to stop.
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Monitoring Engine Parameters
In order for the electronic control system to deliver fuel according to a given set of operating conditions, the following parameters are monitored by the ECU:
• Engine Coolant Temperature (ECT)
• Manifold Air Temperature (MAT)
• Fuel Pressure
• Oil Pressure
• Throttle Position
• Crankshaft Position Sensor
• Pump Position Sensor
• Transfer Pump
• Pump Control Unit
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