DTC P0300 [L3]


DTC P0300	Random misfire detection
DETECTION CONDITION	• PCM monitors CKP sensor input signal interval time. PCM calculates change of interval time for each cylinder. If change of interval time exceeds preprogrammed criteria, PCM detects a misfire in the corresponding cylinder. While the engine is running, the 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	• CKP sensor malfunction • CMP sensor malfunction • Ignition coil malfunction • High-tension lead malfunction • MAF sensor contamination • Excess air suction in intake air system (between MAF sensor and intake manifold) • Fuel pump malfunction • Fuel pressure regulator malfunction • Fuel line clogged • Fuel filter clogged • Fuel leakage in fuel line • Fuel runout • Poor quality fuel • Purge control solenoid valve malfunction • PCV valve malfunction • EGR valve malfunction • Vacuum hoses damages or improper connection • Related connector and terminal malfunction • Related wiring harness malfunction • Insufficient compression


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. • Are any 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 at ON and engine runs at idle?	Yes	Inspect suspected circuit and/or part according to inspection results. (See PCM INSPECTION [L3].) Then go to Step 21.
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. (See PCM INSPECTION [L3].) Then go to Step 21.
5		No	Go to the next step.
6	INSPECT CMP SENSOR • Inspect CMP sensor. (See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [L3].) • Is CMP sensor normal?	Yes	Go to the next step.
6		No	Inspect installation condition of and damage to timing belt and gears, repair faulty parts. • If it is normal, replace CMP sensor. Then go to Step 21.
7	VERIFY CKP SENSOR INSTALLATION CONDITION • Inspect for CKP sensor looseness. • Is CKP sensor loose?	Yes	Retighten CKP sensor, then go to Step 21.
7		No	Go to the next step.
8	INSPECT IGNITION COIL OPERATION AND HIGH-TENSION LEAD WITH TIMING LIGHT • Verify blinking condition for each cylinder using timing light at idle. • Do all cylinders show blinking condition?	Yes	Go to Step 12.
8		No	Go to the next step.
9	INSPECT HIGH-TENSION LEADS OF NON- BLINKING CYLINDER • Turn the ignition switch off. • Inspect high-tension leads for improper installation, corrosion on terminal, open lead and damaged cover. • Is condition of high-tension lead normal?	Yes	Go to the next step.
9		No	Replace faulty high-tension lead, then go to Step 21.
10	INSPECT POWER SUPPLY TERMINAL AT IGNITION COIL CONNECTOR • Disconnect ignition coil connector. • Turn the ignition switch to the ON position (Engine off). • Measure voltage between ignition coil terminal B (wiring harness-side) and body ground. • Is there voltage reading B+?	Yes	Go to the next step.
10		No	Check for open circuit between ignition coil connector and ignition switch. Repair or replace wiring harness, then go to Step 21.
11	INSPECT IGNITION COIL RESISTANCE • Inspect ignition coil resistance. (See IGNITION COIL INSPECTION [L3].) • Is coil resistance normal?	Yes	Go to step 21.
11		No	Replace ignition coil, then go to Step 21.
12	INSPECT MAF PID • Start engine. • Access MAF PID using WDS or equivalent. • Verify that MAF PID changes quickly according to race engine RPM. • Is MAF PID response normal?	Yes	Go to the next step.
12		No	Replace MAF sensor, then go to Step 21.
13	INSPECT EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM • Inspect for air leakage at following: - Between MAF sensor and throttle body - Between throttle body and intake manifold • Is there any malfunction?	Yes	Repair or replace suspected part, then go to Step 21.
13		No	Go to the next step.
14	INSPECT FUEL LINE PRESSURE • Inspect fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [L3].) • Is fuel line pressure normal?	Yes	Go to step 16.
14		No	If fuel line pressure is too low, go to the next step. If fuel line pressure is excessively high, replace fuel pump unit, then go to Step 21.
15	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE • Visually inspect fuel line for any leakage. • Is any fuel leakage found?	Yes	Replace suspected fuel line, then go to Step 21.
15		No	Inspect fuel filters for following: • Restriction or clogging in fuel filter (high-pressure side). • Foreign materials or clogging in fuel filter (low-pressure side) Perform following actions depend on the result above. • If restriction or clogging is found in fuel filter (high-pressure side), replace fuel pump unit. • If foreign materials or clogging is found inside fuel filter (low-pressure side), clean out fuel tank and filter (low-pressure side). • If all items above are normal, replace fuel pump unit. Then, go to Step 21.
16	INSPECT ENGINE COMPRESSION • Inspect engine compression. (See COMPRESSION INSPECTION [L3].) • Is it normal?	Yes	Go to the next step.
16		No	Implement engine overhaul for repairs, then go to Step 21.
17	INSPECT OPERATION OF PURGE CONTROL SOLENOID VALVE • Turn the ignition switch off. • Connect vacuum pump to purge control solenoid valve and apply vacuum to solenoid. • Verify that solenoid holds vacuum. • Turn the ignition switch to the ON position (Engine off). • Access EVAPCP PID in SIMULATION TEST using WDS or equivalent. • Set duty value to 100% for EVAPCP PID. • Apply vacuum while turning solenoid from OFF to ON and simulating EVAPCP PID with 100% duty value. • Verify that solenoid releases vacuum when solenoid is turned to ON. • Is purge control solenoid valve operation normal?	Yes	Go to the next step.
17		No	Replace purge control solenoid valve, then go to Step 21.
18	INSPECT PCV VALVE OPERATION • Turn the ignition switch off. • Remove PCV valve and check valve operation. (See PCV VALVE INSPECTION [L3].) • Is PCV valve operation normal?	Yes	Replace PCV valve, then go to Step 21.
18		No	Go to the next step.
19	INSPECT OPERATION OF EGR VALVE • Remove EGR valve. • Visually inspect for stuck open. • Is EGR valve stuck open?	Yes	Repair or replace EGR valve, then go to Step 21.
19		No	Go to the next step.
20	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 poor sealing of head gasket or other areas between combustion chamber and engine coolant passage. Repair or replace faulty parts, then go to the next step.
20		No	Go to the next step.
21	VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED • Make sure to reconnect all disconnected connectors. • Turn the ignition switch to the ON position (Engine off). • Clear DTC from memory using WDS or equivalent. • Run PCM adaptive memory procedure drive mode. (See OBD DRIVE MODE [L3].) • Is PENDING CODE of same DTC present?	Yes	Replace PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [L3].)
21		No	Go to the next step.
22	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].)
22		No	Troubleshooting completed.