Diagnostic Aids

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix, 2003 Chevrolet Malibu, and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The PCM will NOT enable the catalyst test until following conditions are met:

The engine idle speed is within 150 RPM of the desired idle.
The throttle position is 1.5 percent or less.
The short term integrator is between -20 to 20 percent.

The catalyst test will abort if the vehicle falls outside the conditions listed below while the test is running:

The engine idle speed is within 300 RPM of the desired idle, or within 150 RPM for the w/67.
The throttle position is 1.5 percent or less.
The short term integrator is between -20 to 20 percent.

The catalyst test may abort due to a change in the engine load from the A/C, the coolant fan, or other components. If this condition occurs, use the scan tool to force the cooling fans ON, then return to step 2 in the test.

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

The number of attempted tests is limited to 18 per key cycle.
More than 6 tests may have to be attempted to achieve 6 completed tests. An aborted test counts as an attempted test.
If 18 tests have been attempted, and a decision has not been made this key cycle, turn ignition switch to position OFF for 30 seconds. Start the vehicle and perform the conditions for running the DTC, including the 10 minute engine run time.
After returning to an idle the HO2S 1 signal may stay rich or lean for several seconds causing the test to be delayed.

If the condition is intermittent, go to INTERMITTENTS in TROUBLE SHOOTING - 3.1L CENTURY, GRAND PRIX & MALIBU article.