Diagnostic Aids

Check for the following conditions:

• PCM will not enable catalyst test until the following conditions are met:

  • VIN K
    
    Engine speed is plus or minus 150 RPM from desired idle.
  • VIN 1
    
    Engine speed is plus or minus 600 RPM from desired idle.
  • Throttle Position (TP) is zero percent.
  • Short term integrator is -20-20 percent.
• Catalyst test will abort if vehicle conditions fall outside conditions listed below while test is running:
  1. Engine speed is plus or minus 150 (VIN K) or 600 (VIN 1) RPM from desired idle.
  2. Throttle Position (TP) is 1.5 percent or less.
  3. Short term integrator is -20-20 percent.
NOTE: When using scan tool to force cooling fans on, use NEXT LIST and PREVIOUS LIST soft keys to enter catalyst data list. If catalyst data list is not entered this way, cooling fan control will be canceled.
• Catalyst test may abort due to a change in engine load (i.e., A/C, cooling fan). If this problem occurs, use scan tool to force cooling fans on, then return to step  2 in procedure.
• More than 6 tests may have to be attempted to get 6 completed tests. An aborted test counts as an attempted test.
• Number of attempted tests is limited to 18 per key cycle.
• After returning to idle, HO2S 1 signal may stay rich or lean for several seconds, causing test to be delayed.
• Inspect PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly-formed or damaged terminals, and faulty terminal-to-wire connections. Use a corresponding mating terminal in order to test for proper terminal tension.
• Inspect wiring harness for damage. If harness appears to be okay, observe display on scan tool while moving connectors and wiring harnesses related to sensor. A change in display will indicate location of fault.