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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 sensor - inlet and camshaft position sensor - exhaust 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 00 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 00 is set. DTCs P0301 00 - P0304 00 correspond to cylinders 1-4. If the ECM is able to determine that a specific cylinder that is misfiring, the DTC for that cylinder will 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 00, P0301 00, P0302 00, P0303 00 and P0304 00 are Type A (MIL flashing) or Type B DTCs.

DTCs P0300 00, P0301 00, P0302 00, P0303 00 and P0304 00 are Type A (MIL flashing) or Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

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 .

1. Verify that no other DTCs are set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Engine idling, verify there is no abnormal engine noise.

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

3. If the vehicle passes the circuit/system verification test, operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the freeze frame/failure records lists.

1. Verify that the following conditions do not exist:

•	Vacuum hose splits, kinks, and incorrect connections

•	Engine vacuum leaks

•	Crankcase ventilation system for vacuum leaks, refer to Crankcase Ventilation System Inspection/Diagnosis : LDE, LED, LFJ, LXV, 2H0, LUW, LFH .

•	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 : Diesel .

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

2. Ignition OFF, disconnect the harness connector at the Q17A Fuel Injector 1, Q17B Fuel Injector 2, Q17C Fuel Injector 3, or Q17D Fuel Injector 4.
3. Connect a test lamp between the control circuit terminal 2 and the ignition voltage circuit terminal 1.
4. Engine idling, the test lamp should flash.

⇒	If the test lamp does not flash, refer to DTC P0201, P0202, P0203, or P0204 .

5. Ignition OFF, connect the Q17A Fuel Injector 1, Q17B Fuel Injector 2, Q17C Fuel Injector 3, or Q17D Fuel Injector 4 connector. Remove the T8 Ignition Coil.
6. Inspect the ignition coil 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.

7. Connect the harness connector to the ignition coil assembly.

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

8. Install the EN 36012-A diagnostic harness to the spark plug boots.
9. Install the EL 26792 spark tester between the spark plug boot of the misfiring cylinder and ground.
10. Connect the remaining wires to the appropriate cylinders.

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

11. Attempt to start the engine and observe the EL 26792 spark tester . The spark tester should spark.

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

12. Ignition 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

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

13. Exchange the suspected spark plug with another cylinder that is operating correctly.
14. 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.

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

•	A lean or rich fuel injector, refer to Fuel Injector Diagnosis : Scan Tool  → Special Tool .

•	An engine mechanical condition, refer to Symptoms - Engine Mechanical .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Turn OFF the ignition for 60 s.
5. 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 the Diagnostic Trouble Code (DTC) List - Vehicle .
6. To verify that the performance of the catalyst has not been affected by the condition that set this DTC, perform the repair verification for DTC P0420 00.