Test Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

2: If the actual CKP variation values are not within the learned values, the misfire counters may increment.

DTC P0300

Step	Action	Values	Yes	No
1	Did you perform the Diagnostic System Check-Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	IMPORTANT: You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to CKP System Variation Learn Procedure . Start the engine. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records. Monitor all of the Misfire counters with the scan tool. Are any of the Misfire current counters incrementing?	-	Go to Step 3	Go to Diagnostic Aids
3	Are any other DTCs set?	-	Go to Diagnostic Trouble Code (DTC) List	Go to Step 4
4	Can any abnormal engine noise be heard?	-	Go to Symptoms - Engine Mechanical	Go to Step 5
5	Inspect the following components: The vacuum hoses and seals for splits, restrictions, and improper connections-Refer to Engine Controls Schematics . The throttle body and intake manifold for vacuum leaks The crankcase ventilation system for vacuum leaks-Refer to Crankcase Ventilation System Inspection/Description in Engine Mechanical. The PCM grounds for corrosion and loose connections-Refer to Ground Distribution Schematics in Wiring Systems. The exhaust system for restrictions-Refer to Restricted Exhaust in Engine Exhaust. The fuel for contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) . Did you find and correct the condition?	-	Go to Step 13	Go to Step 6
6	Remove the spark plugs from the cylinders that indicated a misfire. Refer to Spark Plug Replacement . Inspect the spark plug. Refer to Spark Plug Inspection . Do the spark plugs appear to be OK?	-	Go to Step 10	Go to Step 7
7	Are the sparks plug oil or coolant fouled?	-	Go to Symptoms - Engine Mechanical	Go to Step 8
8	Are the spark plugs gas fouled?	-	Go to Step 11	Go to Step 9
9	Did the spark plugs show any signs of being cracked, worn, or improperly gapped?	-	Go to Step 12	Go to Step 10
10	Perform the fuel injector coil test. Refer to Fuel Injector Coil Test . Did you find and correct the condition?	-	Go to Step 13	Go to Symptoms - Engine Mechanical
11	Perform the fuel system diagnosis. Refer to Fuel System Diagnosis . Did you find and correct the condition?	-	Go to Step 13	Go to Symptoms - Engine Mechanical
12	Replace or gap the spark plugs. Refer to Spark Plug Replacement . Did you complete the action?	-	Go to Step 13	-
13	Was the customer concern the MIL flashing?	-	Go to Step 14	Go to Step 15
14	Operate the vehicle at the specified value for 4 minutes. Operate the vehicle within the Conditions for Running the DTC P0420 as specified in the supporting text. Refer to DTC P0420 . Does DTC P0420 run and pass?	2,500 RPM	Go to Step 15	Go to DTC P0420
15	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. 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. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 16
16	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK