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 (ISM) at various engine operating conditions. Test is performed to evaluate Combustion Quality (CQ) signal pulse width if it is within predetermined range. If CQ signal pulse width is out of predetermined range, fail counter will be incremented. If failure counter exceeds calibration, test is complete and a failure record will be reported. If sample counter threshold is reached before failure threshold, then test is complete and a pass will be reported. This test will detect an open or short in CQ line circuit, ION Sensing Module faults and analog input faults in PCM.

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.