RESUMEN DE POLÍTICAS CONTABLES SIGNIFICATIVAS:

Both Additive and Multiplicative adaptation are a form of long term fuel control. Each is a coarse type of FT control, allowing short term FT to maintain a midpoint balance between rich and lean.

C.1.1 Additive Adaptation

Additive means adding or subtracting equal amounts of fuel to every fuel block cell regardless of the programmed base injection pulse value. It works very effectively for idle mixture related problems, but its effect is minimal at the higher engine speeds. For example, vacuum leaks greatly affect fuel mixture at idle but become less severe at higher RPM. The important distinction is that the amount of fuel correction is not dependent upon the original base in each fuel memory cell.

Additive adaptation indicates a fine-tuning, long-term correction or adaptation that the ECM is applying to the fuel injection pulse width. Although these minute adjustments affect the entire engine speed range, they are most noticeable at idle or during lower pulse-width operating conditions. A positive value indicates increased fuel injection duration, and a negative value indicates a decreased fuel injection duration.

When the short term correction value, reaches its upper or lower limit, the ECM resets short term correction and moves the long term FT value up or down by one count. The short term FT moves quickly, while the long term FT moves slowly. The short and long term FT continue to work

is adding directly to the injector opening time for all memory cells. However, data is only updated under certain idle conditions. Be aware that Idle and Part Load Multiplicative work together to establish the long term FT.

C.1.2 Multiplicative Adaptation

Multiplicative means multiplying or taking the preprogrammed cell base value and multiplying that number by either a correction factor or percent. Here, the correction amount increased or decreased in each memory block cell is dependent on each cell’s base injection pulse. This form of adaptation is required to compensate for fuel control-type problems that get worse with increased engine speed (i.e., a faulty injector). Short term FT in VW/Audi language is usually called O2 regulation or O2 control. The readings are constantly changing, directly responding to oxygen sensor (O2S) input. Normal readings are usually in the ±10% range with 0 as the midpoint.

If it gets too far off, Long-term additive or multiplicative adjusts the window back to the midpoint (balanced state).

Multiplicative adaptation correction indicates the long-term FT correction that the ECM is applying to the air/fuel mixture during closed loop operation over the middle to upper range of engine operation. VW/Audi use the term “Multiplicative Mixture Adaptation” because it is a percent correction factor based on the individual base injection value for each memory cell. Cells are constantly updated based on feedback operation. If any cell stores an update that is beyond the neutral feedback value, a correction is then factored into the injector pulse-width calculation. To maintain the optimal air/fuel ratio of 14.7:1 for catalytic converter (CAT) efficiency, the ECM monitors the O2Ss and calculated load. From this information, the ECM calculates a percent value that indicates how much to enrich or dilute the fuel mixture. Sometimes, the ECM makes fine tuning adjustments across the complete fuel map by adjusting the IDLE (Additive) FUEL TRIM (for example, when a fine adjustment is needed across the range to compensate for fuel injector drift).

C.1.3 Examples of Display Groups for Long Term FT Adaptive Value

Depending on the year, vehicle, engine, and engine code, you may see some combination of the following long term FT parameters:

• ADPVALUEO2(ADD)(%)

• ADPVALUEO2(IDLE)(ADD)(%)

• ADPVALUEO2(MUL)(%)

• ADPVALUEO2(P/T)(ADD)(%)

• LEARNO2(ACTUAL)(BANK1)(%)

• LEARNO2(ACTUAL)(BANK2)(%)

• LEARNO2(BANK1)

• LEARNO2(BANK1)(ADD)(%)

• LEARNO2(BANK1)(IDLE)(%)

• LEARNO2(BANK1)(MUL)(%)

• LEARNO2(BANK1)(P/T)(%)

• LEARNO2(BANK2)

• LEARNO2(BANK2)(%)

• LEARNO2(BANK2)(ADD)(%)

• LEARNO2(BANK2)(IDLE)(%)

• LEARNO2(BANK2)(MUL)(%)

• LEARNO2(BANK2)(P/T)(%)

• LEARNO2(BK1-SNS1)(IDLE)(%)

• LEARNO2(BK1-Sensible/T)(%)

• LEARNO2(BK2-SNS1)(IDLE)(%)

• LEARNO2(BK2-SNS1)(P/T)(%)

• LEARNO2(FULL)

• LEARNO2(IDLE)

• LEARNO2(IDLE)(%)

• LEARNO2(IDLE)(ADD)(%)

• LEARNO2(IDLE)(ADD)(%)

• LEARNO2(IDLE)(ms)

• LEARNO2(IDLE)(MUL)(%)

• LEARNO2(P/T)

• LEARNO2(P/T)(%)

• LEARNO2(P/T)(ADD)(%)

• LEARNO2(P/Tumult)(%)

• LEARNO2(P/T-WOT)

• LEARNO2(PART)(MUL)(%)

• LEARNVALUEMIXTUREADAPTATION

• LEARNVALUEMIXTURECORR(%)

• LEARNVALUEMIXTURECORR(ms)

• LEARNVALUEO2(P/T)(ADD)(%)

• LRNO2BEFORECAT(P/T)(ADD)(%)

• LRNO2BEFORECAT(IDLE)(ADD)(%)

• LRNO2BEFORECAT(P/T)(ADD)(%)

• LEARNVALUEO2(IDLE)(ADD)(%)

• LEARNVALUEO2(P/T)(MUL)(%)

• ADPVALUEMIXTURE(BANK1)(%)

• LRNO2BEFORECAT(IDLE)(ADD)(%)

• LEARNMIXT(BANK1)(IDLE)(%)

• LEARNMIXT(BANK1)(P/T)(%)

• LEARNMIXT(BANK1)(P/T1)(%)

• LEARNMIXT(BANK1)(P/T2)(%)

• LEARNMIXT(BANK1)(P/T3)(%)

• LEARNMIXT(BANK2)(IDLE)(%)

• LEARNMIXT(BANK2)(P/T)(%)

• LEARNMIXT(BANK2)(P/T1)(%)

• LEARNMIXTURE(BANK1)(%)

• LEARNMIXTURE(BANK2)(%)

Below is a typical display group, Group (32), “LEARN VALUES O2”.

• LEARN VALUE O2(BK 1)(IDLE)(%)

• LEARN VALUE O2(BK 2)(IDLE)(%)

• LEARN VALUE O2(BK 1)(P/T)(%)

• LEARN VALUE O2(BK 2)(P/T)(%)

C.1.4 Important Tips for Long Term Fuel Control

• The value typically ranges from -10 to +10. A normal operating engine should fluctuate only slightly. If more than ±7%, perform a mixture diagnosis. Technicians report MAF sensor problems with readings of ±5%.

• Use Basic Settings for faster adaptation relearn. Take short road test (usually 2–3 miles) with the scan tool hooked up in Basic Settings. For relearn, make sure the engine is at normal operating temperature (coolant minimum temperature of 167°F [75°C] and a maximum intake air temperature of 194°F [90°C]). For idle relearn, let the engine idle in Basic Settings for a few minutes. For road test in Basic Settings, perform multiple accelerations and decelerations, as well as a part throttle cruise. Check to see that learn values are back within normal range. If OK, clear the codes. Field technicians report faster relearn and verification of repair by not clearing codes until correct fuel control has been confirmed). Finish by setting all Readiness Codes, and then one more final road test (see “Basic Settings and Fuel Trim Accelerated Learning” on page 48).

• Some vehicles may have part throttle learning divided into 3 different parts: (P/T1, P/T2, P/

T3). Check to see that each part is in proper specification.

• For most systems that have FT control using ±25% maximum range, readings above or below 14 sets a DTC and turns on the MIL.