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DTC P0300-P0304

The engine control module (ECM) uses information from the crankshaft position sensor in order to determine when an engine misfire is occurring and uses information from the camshaft position sensors in order to determine which cylinder is misfiring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 sets. Under certain driving conditions, a misfire rate can be high enough to cause the 3-way catalyst to overheat, possibly damaging the converter. The malfunction indicator lamp (MIL) will flash ON and OFF when converter overheating, damaging conditions are present and DTC P0300 is set. DTCs P0301-P0304 correspond to cylinders 1-4. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will also set.

The ECM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission or catalyst damaging levels to exceed mandated standards.

DTCs P0300-P0304 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

For equivalent regional tools, refer to Special Tools : Diagnostic Tools .

1. Engine running at normal operating temperature, verify there is no abnormal engine noise.

⇒	If there is an abnormal engine noise, refer to Symptoms - Engine Mechanical .

2. Observe the DTC information with a scan tool. Verify that DTC P0201-P0204, P0315, P0335, P0336, P0351-P0354 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Note: A misfire may only occur when the engine is under a load. An engine load may be necessary to verify the condition.

3. Observe the scan tool Misfire Current Counter parameters. The Misfire Current Counters should not be incrementing.
4. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

Note: You must perform the Circuit/System Verification first.

1. Verify that the following conditions do not exist:

•	Vacuum hose splits, kinks, and incorrect connections

•	Engine vacuum leaks

•	Crankcase ventilation system vacuum leaks

•	Fuel pressure that is too low or too high--Refer to Fuel System Diagnosis .

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

•	Restricted exhaust system--Refer to Restricted Exhaust .

⇒	If you find any of the above conditions, repair as necessary.

2. Vehicle OFF, remove the K35 ignition coil module harness connector and remove the K35 ignition coil module.
3. Inspect the K35 ignition coil module spark plug boots for the following conditions:

•

Damage

•	Carbon tracking

•	Oil contamination

•	Water intrusion

⇒	If you find any of the above conditions, repair as necessary.

4. Connect the harness connector to the K35 ignition coil module.

Note: It may be necessary to secure the J 36012-A to the spark plug boots with electrical tape.

5. Install the J 36012-A to the spark plug boots.
6. Install the J 26792 between the spark plug boot of the misfiring cylinder and ground.
7. Connect the remaining wires to the appropriate cylinders.

Note: An erratic or weak spark is considered a no spark condition.

8. Attempt to start the engine and observe the J 26792 . The spark tester should spark.

⇒	If there is no spark, refer to Electronic Ignition System Diagnosis .

9. Vehicle OFF, remove the spark plug from the misfiring cylinder. Verify the following conditions do not exist with the spark plug:

•	Gas, coolant, or oil fouled--Refer to Spark Plug Inspection .

•	Cracked, worn, incorrectly gapped--Refer to Ignition System Specifications .

⇒	If there is a condition with the spark plug, replace the spark plug.

10. Exchange the suspected spark plug with another cylinder that is operating correctly.
11. Engine running, observe the scan tool Misfire Current Counters. The misfire should not follow the spark plug exchange.

⇒	If the misfire follows the spark plug, replace the spark plug.

12. If all conditions test normal, test or inspect for the following:

•	A lean or rich fuel injector--Refer to Fuel Injector Solenoid Coil Test .

•	An engine mechanical condition--Refer to Symptoms - Engine Mechanical .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.
3. Clear the DTCs with a scan tool.
4. Vehicle OFF for 60 s.
5. Engine running, observe the Misfire Current Counters with a scan tool. The Misfire Current Counters should not be incrementing.

⇒	If the Misfire Current Counters are incrementing, a misfire still exists.

6. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the freeze frame/failure records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.
7. To verify that the performance of the catalytic converter has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420. Refer to DTC P0420 .