Chrysler Voyager 2000 GS Скачать руководство пользователя страница 14

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MAP voltage rapidly changing

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Severe engine decel

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TPS toggling OPEN/CLOSED

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Engine RPM too low (RPM levels by vehicle)

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Engine RPM too high (RPM levels vary by vehi-

cle)

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Full Lean or Decel Fuel Shut-off

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Cold start

FUEL SYSTEM MONITOR

To comply with clean air regulations, vehicles are

equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide. The catalyst works best
when the air fuel (A/F) ratio is at or near the opti-
mum of 14.7 to 1.

The PCM is programmed to maintain the optimum

air/fuel ratio of 14.7 to 1. This is done by making
short term corrections in the fuel injector pulse width
based on the O2S output. The programmed memory
acts as a self calibration tool that the engine control-
ler uses to compensate for variations in engine spec-
ifications, sensor tolerances and engine fatigue over
the life span of the engine. By monitoring the actual
air-fuel ratio with the O2S (short term) and multiply-
ing that with the program long-term (adaptive) mem-
ory and comparing that to the limit, it can be
determined whether it will pass an emissions test. If
a malfunction occurs such that the PCM cannot
maintain the optimum A/F ratio, then the MIL will
be illuminated.

Monitor Operation— Fuel systems monitors do

not have a pre-test because they are continuously
running monitors. Therefore, the PCM constantly
monitors Short Term Compensation and Long Term
Adaptive memory.

Lean: If at anytime during a lean engine operation,

short term compensation multiplied by long term
adaptive

exceeds

certain

percentage

for

extended period, the PCM sets a Fuel System Lean
Fault for that trip and a Freeze Frame is entered.

Rich: If at anytime during a rich operation, Short

Term Compensation multiplied by Long Term Adap-
tive is less than a predetermined value, the PCM
checks the Purge Free Cells.

Purge Free Cells are values placed in Adaptive

Memory cells when the EVAP Purge Solenoid is OFF.
Two, three or four Purge Free cells are used. One cor-
responds to an Adaptive Memory cell at idle, the
other to a cell that is off-idle. For example, if a Purge
Free cell is labeled PFC1, it would hold the value for
Adaptive Memory cell C1 under non-purge condi-
tions.

If all Purge Free Cells are less than a certain per-

centage, and the Adaptive Memory factor is less than
a certain percentage, the PCM sets a Fuel System

Rich fault for that trip and a Freeze Frame is
entered.

The Fuel Monitor is a two trip monitor. The PCM

records engine data in Freeze Frame upon setting of
the first fault, or maturing code. When the fuel mon-
itor fails on a second consecutive trip, the code is
matured and the MIL is illuminated. The stored
Freeze Frame data is still from the first fault.

In order for the PCM to extinguish the MIL, the

Fuel Monitor must pass in a Similar Condition Win-
dow. The similar conditions relate to RPM and load.
The engine must be within a predetermined percent-
age of both RPM and load when the monitor runs to
count a good trip. As with all DTCs, three good trips
are required to extinguish the MIL and 40 warm up
cycles are required to erase the DTC. If the engine
does not run in a Similar Conditions Window, the
Task Manager extinguishes the MIL after 80 good
trips.

Enabling Conditions— The following conditions

must be met to operate the fuel control monitor:

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PCM not in fuel crank mode (engine running)

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PCM in Closed Loop fuel control

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Fuel system updating Long Term Adaptive

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Fuel level above 15% of capacity

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Fuel level below 85% of capacity