Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

The control module uses information from the ignition control module (ICM) and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the control module is able to detect individual misfire events. A misfire rate that is high enough can cause the 3-way catalytic converter (TWC) to overheat under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC overheating are present. If the control module detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets.

The control module is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second ignition cycle the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. The control module illuminates the malfunction indicator lamp (MIL) when one of the following occur:

You must perform the Crankshaft Position System Variation Learn before proceeding with this diagnostic procedure.

Schematic Reference

Electrical Information Reference

Scan Tool Reference

Special Tools Required

J 26792 Spark Tester

1. There should be no abnormal engine noise.
2. Diagnose any other DTCs that are set. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
3. Observe the Misfire Current Counters with a scan tool.
4. Operate the engine within the conditions listed in the Freeze Frame/Failure Records.
5. The engine should not be misfiring.

1. If DTCs P0201-P0206 are set, diagnose those DTCs first.
2. Operate the engine within the conditions listed in the Freeze Frame/Failure Records.
3. A current misfire should not be indicated.

⇒	If a single cylinder Current Misfire is indicated, inspect the following components of the affected cylinder for proper operation:

•	The spark plug--Refer to Spark Plug Inspection .

•	The fuel injector--Refer to Fuel Injector Diagnosis .

⇒	If more than one cylinder is randomly misfiring, inspect the following components condition and operation:

•	The ignition coil--Refer to Electronic Ignition (EI) System Diagnosis .

•	The vacuum hoses and seals--Refer to Evaporative Emissions Hose Routing Diagram .

•	The throttle body and intake manifold

•	The brake booster hose

•	The crankcase ventilation system--Refer to Crankcase Ventilation System Inspection/Diagnosis .

•	The control module grounds

•	The exhaust system--Refer to Restricted Exhaust .

•	The fuel--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	The spark plugs--Refer to Spark Plug Inspection .

If the customer concern was a flashing MIL, perform the following procedure:

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

⇒	If the DTC fails this ignition, a misfire still exists.

5. Operate the vehicle at 2,500 RPM for 4 minutes.
6. Operate the vehicle within the Conditions for Running DTCs P0420 and P0430. Refer to DTC P0420 and DTC P0430 .

⇒	If DTC P0420 or P0430 does not run and pass, diagnose those DTCs.