DTC P0301, P0302, P0303, P0304 [L3]


DTC P0301 DTC P0302 DTC P0303 DTC P0304	Cylinder No.1 misfire detection Cylinder No.2 misfire detection Cylinder No.3 misfire detection Cylinder No.4 misfire detection
DETECTION CONDITION	• PCM monitors CKP sensor input signal interval time. PCM calculates the change of interval time for each cylinder. If the change of interval time exceeds the preprogrammed criteria, PCM detects a misfire in the corresponding cylinder. While the engine is running, PCM counts number of misfires that occurs at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates misfire ratio for each crankshaft revolution. If the ratio exceeds the preprogrammed criteria, PCM determines that a misfire, which can damage catalytic converter or affect emission performance, has occurred. Diagnostic support note • This is a continuous monitor (MISFIRE). • MIL illuminates if PCM detects the misfire which affects emission performance in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. • MIL flashes if PCM detects the misfire which can damage the catalytic converter during first drive cycle. Therefore, PENDING CODE is not available while MIL flashes. • PENDING CODE is available if PCM detects the misfire which affects emission performance during first drive cycle. • FREEZE FRAME DATA is available. • DTC is stored in the PCM memory.
POSSIBLE CAUSE	• Spark plug malfunction • High-tension lead malfunction • Fuel injector malfunction • Air suction in intake air system (between dynamic chamber and cylinder head) • Inadequate engine compression due to engine internal malfunction • Related connector or terminal malfunction • Related wiring harness malfunction


STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
1		No	Record FREEZE FRAME DATA on repair order, then go to the next step.
2	VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Check for related Service Information availability. • Is any related Service Information available?	Yes	Perform repair or diagnosis according to available Service Information. • If 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. • Is other DTCs present?	Yes	Go to appropriate DTC troubleshooting. (See DTC TABLE [L3].)
3		No	Go to the next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO THE ON POSITION/IDLE) • Access BOO, ECT, IAT, MAF, RPM, TP and VSS PIDs using WDS or equivalent. (See PCM INSPECTION [L3].) • Is there any signal that is far out of specification when ignition switch is ON and engine runs at idle?	Yes	Inspect suspected circuit and/or part according to inspection results. Then go to Step 12. (See PCM INSPECTION [L3].)
4		No	Go to the next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION • Inspect same PIDs as in Step 4 while simulating FREEZE FRAME DATA condition. • Is there any signal which causes drastic changes?	Yes	Inspect suspected circuit and/or part according to inspection results. Then go to Step 12. (See PCM INSPECTION [L3].)
5		No	Go to the next step.
6	INSPECT SPARK PLUG CONDITION • Turn the ignition switch off. • Remove spark plug from suspected cylinder. • Check spark plug condition: - Cracks - Excess wear - Gap - Wet • Is any problem found on spark plug?	Yes	• If spark plug is wet, fuel flooding is suspected. Go to step 12. • If spark plug has cracks, excessive wear or improper gap, replace faulty spark plug. Then go to Step 12.
6		No	Go to the next step.
7	VERIFY HIGH-TENSION LEAD CONDITION • Remove high-tension lead. • Check high-tension lead condition and resistance. - Cracks - Spark shorts to cylinder head through high-tension lead insulator • Is high-tension lead normal?	Yes	Go to the next step.
7		No	Replace high-tension lead, then go to Step 12.
8	INSPECT FOR AIR SUCTION AT INTAKE-AIR SYSTEM • Inspect for air leakage at 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 12.
8		No	Go to the next step.
9	INSPECT FUEL INJECTOR HARNESS • Remove intake air system parts. • Disconnect fuel injector connector on suspected cylinder. • Connect noid light to fuel injector connector terminals. • Inspect dimming of light during cranking. • Does noid light illuminate?	Yes	Go to the next step.
9		No	Check fuel injector harnesses. Repair or replace it if necessary, then go to Step 12.
10	INSPECT SEALING OF ENGINE COOLANT PASSAGE Warning • Removing radiator cap when radiator is hot is dangerous, Scalding coolant and steam may shoot out and cause serious injury. • When removing radiator cap, wrap thick cloth around and turn it slowly. • Remove radiator cap. • Implement procedure to bleed air from engine coolant, then run engine at idle. • Are there any small bubbles which makes engine coolant white at filler opening? Note • Large bubbles are normal since they are due to remaining air being released from engine coolant passage.	Yes	Air gets in due to poor sealing of head gasket or other areas between combustion chamber and engine coolant passage. Repair or replace faulty parts, then go to Step 12.
10		No	Go to the next step.
11	INSPECT ENGINE COMPRESSION • Inspect engine compression. (See COMPRESSION INSPECTION [L3].) • Is engine compression normal?	Yes	Go to the next step.
11		No	Overhaul the engine, then go to the next step.
12	INSPECT FUEL INJECTOR OPERATION • Remove fuel injector from suspected cylinder. • Swap injector with injector of another cylinder. • Start engine and run it at idle. • Is misfire DTC for cylinder which has suspected fuel injector?	Yes	Replace injector, then go to step 13.
12		No	Go to the next step.
13	VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED • Make sure to reconnect all disconnected connectors. • Start engine. • Clear DTC from PCM memory using WDS or equivalent. • Run PCM adaptive memory procedure drive mode. (See OBD DRIVE MODE [L3].) • Is PENDING CODE or stored code of same DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L3].)
13		No	Go to the next step.
14	VERIFY AFTER REPAIR PROCEDURE • Perform "After Repair Procedure". (See AFTER REPAIR PROCEDURE [L3].) • Is there any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [L3].)
14		No	Troubleshooting completed.