Diagnostic Aids

WARNING: This page is about a different car, the 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect for the following possible sources:
- A tire or wheel that is out of round or out of balance
- Variable thickness brake rotors
- An unbalanced drive shaft
- Certain rough road conditions
- A damaged accessory drive component or belt
A misfire DTC could be caused by a camshaft actuator stuck in the full advance or retard position.
For an intermittent condition, refer to Intermittent Conditions .

DTC P0301 - P0306 Cylinder Misfire Detected

Step	Action	Yes	No
Schematic Reference: Engine Controls Schematics
1	Did you perform the Diagnostic System Check-Engine Controls?	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	Were you sent here from DTC P0300?	Go to Step 3	Go to DTC P0300
3	Turn OFF the ignition. Remove the ignition coil of the misfiring cylinder, but leave the electrical connector connected. Refer to the appropriate procedure: Ignition Coil(s) Replacement - Bank 1 Ignition Coil(s) Replacement - Bank 2 Inspect the ignition coil boot for the following conditions: Holes Tears Carbon tracking Oil contamination or water intrusion Did you find a condition with the ignition coil boot?	Go to Step 12	Go to Step 4
4	Remove the fuel pump fuse from the underhood electrical center. Install the J 26792 Spark Tester to the ignition coil boot and a good ground. Crank the engine while observing the J 26792 . Does the spark tester spark and is the spark consistent?	Go to Step 5	Go to Electronic Ignition (EI) System Diagnosis
5	Turn OFF the ignition. Remove the spark plug from the cylinder that indicated a misfire. Inspect the spark plug. Refer to Spark Plug Inspection . Does the spark plug appear to be OK?	Go to Step 9	Go to Step 6
6	Is the spark plug oil or coolant fouled?	Go to Symptoms - Engine Mechanical in Engine Mechanical - 3.6L (LY7)	Go to Step 7
7	Is the spark plug gas fouled?	Go to Step 10	Go to Step 8
8	Does the spark plug show any signs of being cracked, worn, or incorrectly gap?	Go to Step 11	Go to Step 9
9	Swap the suspected spark plug with another cylinder that is operating correctly. Start the engine. Operate the engine within the conditions that the misfire occurred. Monitor the Misfire Current Counters with a scan tool. Did the misfire move with the spark plug?	Go to Step 11	Go to Step 10
10	IMPORTANT: Make sure all the fuel injectors operate. High resistance in an fuel injector circuit causes the fuel injector to be inoperative without setting a fuel injector DTC. Return to this diagnostic after you complete the Fuel Injector Coil Test. 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 in Engine Mechanical - 3.6L (LY7)
11	Replace the spark plug. Refer to Spark Plug Replacement . Did you complete the replacement?	Go to Step 13	-
12	Replace the ignition coil. Refer to Ignition Coil(s) Replacement - Bank 1 and Ignition Coil(s) Replacement - Bank 2 . Did you complete the replacement?	Go to Step 13	-
13	Was the customer's concern that the malfunction indicator lamp (MIL) is flashing?	Go to DTC P0420 or P0430	Go to Step 14
14	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 15
15	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