Diagnostic Aids

PCM will NOT enable catalyst test until engine speed is 150 RPM +/- from desired idle, Throttle Position (TP) is less than 0.5 percent and short term integrator is -20 to +20 percent. Catalyst test will abort if above conditions are not met. Catalyst test may abort due to a change in engine load due to A/C, coolant fan, or other components. If this condition occurs, use scan tool to force cooling fans on. Return to step  3, then repeat the test.

When using scan tool to force cooling fans on, use list and use previous list soft keys to enter catalyst data list. If the catalyst data list is not entered this way, cooling fan control will be canceled.

• The number of attempted tests is limited to 18 per key cycle.
• You may need to attempt more than 6 tests to complete 6 tests. An aborted test counts as an attempted test.
• If 18 tests have been attempted and a decision has not been made during this key cycle, turn ignition off for 30 seconds. Start engine, and perform items under CODE ENABLE CRITERIA , including 10-minute run time.
• After returning to idle, HO2S 1 signal may stay rich or lean for several seconds causing test to be delayed.

If problem is intermittent, see INTERMITTENT TROUBLE CODE DETERMINATION  under SELF-DIAGNOSTIC SYSTEM.