Test Description

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 - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
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 - Vehicle	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 Emission Hose Routing Diagram . The throttle body and intake manifold for vacuum leaks The crankcase ventilation system for vacuum leaks-Refer to Crankcase Ventilation System Inspection/Description . 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 (with Special Tool) . Did you find and correct the condition?	-	Go to Step 13	Go to Step 6
6	Turn OFF the ignition. Remove the fuel pump relay. Refer to Relay Replacement (Within an Electrical Center) or Relay Replacement (Attached to Wire Harness) in Wiring Systems. Remove the ignition coil for the affected cylinder, keeping the ignition connected to the harness connector. Refer to Ignition Coil(s) Replacement . IMPORTANT: Not grounding the ignition coil may cause an erratic spark. Connect a jumper wire between the ignition coil and a good ground. Install the J 26792 Spark Tester on the ignition coil and a good ground. See Special Tools . Crank the engine. Does the spark tester spark?	-	Go to Step 8	Go to Step 7
7	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 15	Go to Electronic Ignition (EI) System Diagnosis
8	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 9	Go to Step 10
9	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 15	Go to Step 13
10	Is the spark plug oil or coolant fouled?	-	Go to Symptoms - Engine Mechanical	Go to Step 11
11	Is the spark plug gas fouled?	-	Go to Step 13	Go to Step 12
12	Did the spark plug show any signs of being cracked, worn, or improperly gapped?	-	Go to Step 14	Go to Step 13
13	Perform the fuel injector coil test. Refer to Fuel Injector Coil Test . Did you find and correct the condition?	-	Go to Step 15	Go to Symptoms - Engine Mechanical
14	Replace or gap the spark plug. Refer to Spark Plug Replacement . Did you complete the action?	-	Go to Step 16	-
15	Replace the faulty spark plug. Refer to Spark Plug Replacement . Did you complete the replacement?	-	Go to Step 16	-
16	Was the customer concern the malfunction indicator lamp (MIL) flashing?	-	Go to Step 17	Go to Step 18
17	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 18	Go to DTC P0420
18	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 19
19	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