Diagnostic procedure

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DTC P0301, P0302, P0303, P0304 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS (Misfire related) been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line repair information availability. Is any related repair information available?	Yes	Perform repair or diagnosis according to the available repair information. If the vehicle is not repaired, go to the next step.
2		No	Go to the next step.
3	VERIFY RELATED PENDING CODE OR STORED DTCs Turn the ignition switch off then to the ON position (Engine off). Verify related pending code or stored DTCs. Are other DTCs present?	Yes	Go to the appropriate DTC troubleshooting. (See DTC TABLE ).
3		No	Go to the next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON/IDLE) Access APP1, APP2, ECT, IAT, MAF, RPM, TP and VSS PIDs using the WDS or equivalent. (See PCM INSPECTION ). Is there any signal that is far out of specification when the ignition switch is turned to the ON position and the engine idles?	Yes	Inspect the suspected circuit and/or part according to inspection results. Then go to Step 15. (See PCM INSPECTION ).
4		No	Go to the next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION Inspect the same PIDs as in Step 4 while simulating the FREEZE FRAME DATA condition. Is there any signal which causes drastic changes?	Yes	Inspect the suspected circuit and/or part according to inspection results. Then go to Step 15. (See PCM INSPECTION ).
5		No	Go to the next step.
6	INSPECT SPARK PLUG CONDITION Turn the ignition switch off. Remove the spark plug from the suspected cylinder. Inspect the spark plug condition: Cracks Excess wear Gap Wetness Is there any problem found on the spark plug?	Yes	If a spark plug is wet, fuel flooding is suspected. Then go to Step 15. If a spark plug has cracks, excessive wear or an improper gap, replace the malfunctioning spark plug. Then go to Step 15.
6		No	Go to the next step.
7	INSPECT INTAKE-AIR SYSTEM FOR AIR SUCTION Inspect for air leakage at the following: Around connection of dynamic chamber and intake manifold Around connection of intake manifold and cylinder head Is air leakage found?	Yes	Repair or replace suspected part, then go to Step 15.
7		No	Go to the next step.
8	INSPECT SEALING OF ENGINE COOLANT PASSAGE Perform "ENGINE COOLANT LEAKAGE INSPECTION." (See ENGINE COOLANT LEAKAGE INSPECTION ). Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Then go to Step 15.
8		No	Go to the next step.
9	INSPECT FUEL INJECTOR WIRING HARNESS Remove the intake air system parts. Disconnect the fuel injector connector on suspected cylinder. Connect the NOID LIGHT to the fuel injector terminals. Inspect the light dim during cranking. Does the light not illuminate?	Yes	Go to the next step.
9		No	Inspect the fuel injector wiring harnesses. Repair or replace if necessary, then go to Step 15.
10	INSPECT IGNITION COIL HARNESSES Inspect the ignition coil related wiring harness condition (intermittent open or short circuit) of the suspected cylinder. Are the wiring harness conditions normal?	Yes	Go to the next step.
10		No	Repair the suspected wiring harnesses, then go to Step 15.
11	INSPECT IGNITION SYSTEM OPERATION Carry out the spark test. (See SPARK TEST ). Is a strong blue spark visible at the suspected cylinder?	Yes	Go to the next step.
11		No	Repair or replace the malfunctioning part according to the spark test result. Then go to Step 15.
12	INSPECT ENGINE COMPRESSION Inspect the engine compression. (See COMPRESSION INSPECTION ). Is the engine compression normal?	Yes	Go to the next step.
12		No	Overhaul the engine, then go to the next step.
13	INSPECT FUEL INJECTOR OPERATION Connect the WDS or equivalent to DLC-2. Access INJ#1, INJ#2, INJ#3, INJ#4 PIDs. Start the engine and warm it up to the normal operating temperature. Turn the fuel injector off from on using the PID simulation function. Does the engine speed decrease while the fuel injectors are turned off?	Yes	Go to the Step 15.
13		No	Go to the next step.
14	INSPECT INJECTOR DRIVER MODULE Inspect the injector driver module and the related wiring harness. (See INJECTOR DRIVER MODULE INSPECTION ). Is there any malfunction?	Yes	Go to the next step.
14		No	Inspect and replace the fuel injector for the cylinder in which the engine speed does not decrease. Then go to the next step. (See FUEL INJECTOR OPERATION INSPECTION ).
15	VERIFY IF TROUBLESHOOTING OF MISFIRE DTC COMPLETED Make sure to reconnect all disconnected connectors. Start the engine. Clear the DTC from the PCM memory using the WDS or equivalent. Perform the HO2S heater, HO2S, and TWC Repair Verification Drive Mode. (See OBD-II DRIVE MODE ). Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
15		No	Go to the next step.
16	VERIFY AFTER REPAIR PROCEDURE Perform the "AFTER REPAIR PROCEDURE". (See AFTER REPAIR PROCEDURE ). Are any DTCs present?	Yes	Go to the applicable DTC troubleshooting. (See DTC TABLE ).
16		No	Troubleshooting completed.