Circuit Description
WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
PCM checks validity of signals used in ION Sensing Module under following conditions:
- Deceleration Fuel Cut Off (DFCO) test is performed to evaluate Combustion Quality (CQ) signal pulse width.
- If CQ signal pulse width is below a predetermined value, than expected during DFCO conditions. If CQ signal pulse width is more than predetermined threshold, fail counter will be incremented. If failure counter exceeds calibration, test is complete and a failure is reported.
- Power Enrichment (PE) test is performed to evaluate CQ signal pulse width if it is less than predetermined value expected during PE conditions.
- If CQ signal pulse width is above the predetermined threshold, fail counter will be incremented. If failure counter exceeds calibration, test is complete and a failure is reported.
- Combustion Quality (CQ) test is performed to check if inappropriate CQ signal status were detected. If missing CQ pulses, multiple CQ pulses or CQ pulse width calculation errors were detected, failure counter will be incremented. If failure counter exceeds calibration, test is complete and a failure will be reported.
When DTC sets, PCM illuminates MIL as soon as fault was detected. PCM calculates an air flow value based on idle air control valve position, throttle position, RPM and barometric pressure. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data.
PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.