Diagnostic Aids

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.

Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. If harness appears to be okay, use scan tool to observe HO2S readings while moving connectors and harnesses. A change in display will indicate location of fault. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

By using TECH 2 scan tool in TWC MONITOR TEST COUNTER mode TWC diagnostic test can be monitored. To complete TWC diagnostic test, counter must be allowed to count 49 samples and roll over to zero at least twice. A bad catalytic convertor will require 3 or more 50 sample tests to report failure.

Difficulty completing DTC P0420 or P0430 STATUS THIS IGN test may be encountered in areas where test conditions cannot be maintained easily, especially in urban areas. To minimize amount of driving time required to complete test, use following procedure:

Start engine, and allow engine to warm completely.
With vehicle in Park, use scan tool to monitor MAF sensor flow. Hold throttle at part throttle opening that allows for a MAF sensor reading of over 12 grams per/sec for 2 minutes or more.
When test driving vehicle, operate vehicle in second or third gear to allow vehicle to remain in DTC P0420 or P0430 test conditions as described in CODE ENABLE CRITERIA . If stopping is required during test drive, place vehicle in Park and hold throttle at part throttle opening that allows for a MAF sensor reading of over 15 grams per/sec during duration of stop.