Test Description

WARNING: This page is about a different car, the 2007 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number 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 - Vehicle?	-	Go to Step 2	Go to DIAGNOSTIC SYSTEM CHECK - VEHICLE
2	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 Intermittent Conditions
3	Are any other DTCs set?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 4
4	Can any abnormal engine noise be heard?	-	Go to Symptoms - Engine Mechanical	Go to Step 5
5	Start and idle the engine. Compare the manifold absolute pressure (MAP) voltage indicated by the scan tool with the typical scan data. Refer to Scan Tool Data List . Is the indicated value more than the typical value?	-	Go to DTC P0108	Go to Step 6
6	Inspect the following components: The vacuum hoses and seals for splits, restrictions, and improper connections-Refer to Emission Hose Routing Diagram . The crankcase ventilation system for vacuum leaks-Refer to Crankcase Ventilation System Inspection/Diagnosis . The powertrain control module (PCM) grounds for corrosion and loose connections-Refer to Ground Distribution Schematics . The exhaust system for restrictions-Refer to Restricted Exhaust . The fuel for contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special Tool) . Did you find and correct the condition?	-	Go to Step 20	Go to Step 7
7	Turn OFF the ignition. Remove the fuel pump relay. Refer to Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Electrical Center) . Remove the ignition coil for the affected cylinder, keeping the ignition connected to the harness connector. Refer to Ignition Coil Replacement . Install the J 26792 Spark Tester on the ignition coil and a good ground. Crank the engine. Does the spark tester spark?	-	Go to Step 9	Go to Step 8
8	Inspect the affected cylinder spark plug boot for a missing or damaged ignition coil spring. Did you find and correct the condition?	-	Go to Step 16	Go to Electronic Ignition (EI) System Diagnosis
9	Remove the spark plug from the cylinder that indicated a misfire. Refer to Spark Plug Replacement . Inspect the spark plug. Refer to Spark Plug Inspection . Does the spark plug appear to be OK?	-	Go to Step 10	Go to Step 11
10	Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement . Operate the vehicle under the same conditions that the misfire occurred. Did the misfire move with the spark plug?	-	Go to Step 17	Go to Step 14
11	Is the spark plug oil or coolant fouled?	-	Go to Symptoms - Engine Mechanical	Go to Step 12
12	Is the spark plug gas fouled?	-	Go to Step 15	Go to Step 13
13	Did the spark plug show any signs of being cracked, worn, or improperly gapped?	-	Go to Step 16	Go to Step 14
14	Perform the fuel injector coil test. Refer to Fuel Injector Diagnosis (w/J39021 or w/Tech 2) or Fuel Injector Diagnosis (w/CH47976) . Did you find and correct the condition?	-	Go to Step 18	Go to Symptoms - Engine Mechanical
15	Perform the fuel system diagnosis. Refer to Fuel System Diagnosis . Did you find and correct the condition?	-	Go to Step 18	Go to Symptoms - Engine Mechanical
16	Replace or gap the spark plug. Refer to Spark Plug Replacement . Did you complete the action?	-	Go to Step 18	-
17	Replace the faulty spark plug. Refer to Spark Plug Replacement . Did you complete the replacement?	-	Go to Step 18	-
18	Was the customer concern the MIL flashing?	-	Go to Step 19	Go to Step 20
19	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 the DTC run and pass?	2,500 RPM	Go to Step 20	Go to DTC P0420
20	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 21
21	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	System OK