Diagnostic Aids

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when you diagnose or replace the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.

For any test that requires probing the PCM or component harness connectors, use the J 35616-A connector test adapter kit. Using this kit prevents any damage to the harness connector terminals.

The following conditions may cause a misfire:

Running the vehicle out of fuel causes sufficient misfire to set DTC P0300. A vehicle that is out of fuel may have DTC P0461 also set.
A restricted fuel filter can cause sufficient misfire to set DTC P0300.
A misfire may not be apparent at idle. The misfire may only occur above idle under a load. Road-test the vehicle, and monitor the misfire current counters.
If more than one cylinder is misfiring, the scan tool may only display one cylinder misfiring. This condition will not be apparent until you complete the repair. Also, if an ignition coil or module ground circuit is open for one side of the engine, the scan tool may only display 2 or 3 cylinders misfiring. Inspect the ground circuit for the ignition coil or modules on the cylinder bank of the engine that has more than one cylinder misfiring.
Excessive vibration from sources other than the engine could cause a misfire DTC. The following conditions are possible sources of vibration:
- A variable thickness brake rotor.
- A drive shaft that is not balanced.
- Certain rough road conditions.

Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. See INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.