DTC P0300 [LF ATX (FN4A-EL), L3 ATX]

DTC P0300	Random misfire detected
DETECTION CONDITION	• The PCM monitors CKP sensor input signal interval time. The PCM calculates change of interval time for each cylinder. If change of interval time exceeds preprogrammed criteria, the PCM detects misfire in the corresponding cylinder. While the engine is running, the PCM counts number of misfires that occurred at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates misfire ratio for each crankshaft revolution. If the ratio exceeds the preprogrammed criteria, the 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). • The MIL illuminates if the 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. • The MIL flashes if the PCM detects the misfire which can damage the catalytic converter during first drive cycle. • PENDING CODE is available if the 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 • Ignition system malfunction • MAF sensor contamination • Excess air suction in intake air system (between MAF sensor and intake manifold) • Fuel pump malfunction • Fuel pressure regulator (built-in fuel pump unit) 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 • Variable valve timing control system improper

DTC P0300

Random misfire detected

DETECTION CONDITION

• The PCM monitors CKP sensor input signal interval time. The PCM calculates change of interval time for each cylinder. If change of interval time exceeds preprogrammed criteria, the PCM detects misfire in the corresponding cylinder. While the engine is running, the PCM counts number of misfires that occurred at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates misfire ratio for each crankshaft revolution. If the ratio exceeds the preprogrammed criteria, the 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).

• The MIL illuminates if the 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.

• The MIL flashes if the PCM detects the misfire which can damage the catalytic converter during first drive cycle.

• PENDING CODE is available if the 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

• Ignition system malfunction

• MAF sensor contamination

• Excess air suction in intake air system (between MAF sensor and intake manifold)

• Fuel pump malfunction

• Fuel pressure regulator (built-in fuel pump unit) 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

• Variable valve timing control system improper

STEP	INSPECTION	ACTION
1	VERIFY FREEZE FRAME DATA HAVE BEEN RECORDED • Have FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
No	Record the FREEZE FRAME DATA on repair order, then go to the next step.
2	VERIFY RELATED SERVICE INFORMATION AVAILABILITY • Verify related Service Information availability. • Is any related Service Information available?	Yes	Perform repair or diagnosis according to the available Service Information. • If the vehicle is not repaired, go to the next step.
No	Go to the next step.
3	VERIFY RELATED PENDING CODE OR STORED DTC • 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 [LF ATX (FN4A-EL), L3 ATX].)
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 M-MDS. (See PCM INSPECTION [LF, L3].) • 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 suspected circuit and/or part according to inspection results. (See PCM INSPECTION [LF, L3].) Then go to Step 20.
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 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 [LF, L3].) Then go to Step 20.
No	Go to the next step.
6	INSPECT CMP SENSOR • Inspect CMP sensor. (See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [LF, L3].) • Is CMP sensor normal?	Yes	Go to the next step.
No	Inspect installation condition and damages on timing chain and gears, repair the malfunctioning part. • If it is normal, replace the CMP sensor. Then go to Step 20.
7	VERIFY CKP SENSOR INSTALLATION CONDITION • Inspect for CKP sensor looseness. • Is CKP sensor loosen?	Yes	Retighten the CKP sensor, then go to Step.
No	Go to the next step.
8	INSPECT IGNITION COIL HARNESSES • Inspect the ignition coil related harness condition (intermittent open or short) for all cylinders. • Are harness conditions normal?	Yes	Go to the next step.
No	Repair suspected wiring harnesses, then go to Step 20.
9	INSPECT IGNITION SYSTEM OPERATION • Carry out spark test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF, L3]) • Is strong blue spark visible at each cylinder?	Yes	Go to the next step.
No	Repair or replace malfunctioning part according to spark test result. Then go to Step 20.
10	INSPECT MAF PID • Start the engine. • Access MAF PID using the M-MDS. • Race the engine and verify that MAF PID changes quickly according to change in the engine speed. • Is MAF PID response normal?	Yes	Go to the next step.
No	Replace the MAF sensor, then go to Step 20.
11	INSPECT EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM • Inspect for air leakage at following: ― Between the 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 20.
No	Go to the next step.
12	INSPECT FUEL LINE PRESSURE • Inspect fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [LF, L3].) • Is fuel line pressure normal?	Yes	Go to Step 14.
No	If the fuel line pressure is too low, go to the next step. If the fuel line pressure is excess high, replace the fuel pump unit, then go to Step 20.
13	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE • Visually inspect fuel line for fuel leakage. • Is there any fuel leakage?	Yes	Replace suspected fuel line, then go to Step 20.
No	Inspect fuel filters for following: • Foreign materials or stain inside fuel filter (low-pressure side) Perform following actions depend on the result above. • If foreign materials or stain is found inside fuel filter (low-pressure side), clean the fuel tank and filter (low-pressure side). • If normal, replace the fuel pump unit. Then, go to Step 20.
14	INSPECT ENGINE COMPRESSION • Inspect engine compression. (See COMPRESSION INSPECTION [LF, L3].) • Is it normal?	Yes	Go to the next step.
No	Perform engine overhaul for repairs, then go to Step 20.
15	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION • Inspect variable valve timing control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF, L3]) • Does variable valve timing control system work properly?	Yes	Go to the next step.
No	Repair or replace malfunctioning part according to variable valve timing control system inspection results, then go to Step 20.
16	INSPECT OPERATION OF PURGE CONTROL SOLENOID VALVE • Turn the ignition switch off. • Connect the 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 the M-MDS. • 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 while solenoid is turned ON. • Is purge control solenoid valve operation normal?	Yes	Go to the next step.
No	Replace the purge control solenoid valve, then go to Step 20.
17	INSPECT PCV VALVE OPERATION • Turn the ignition switch off. • Remove PCV valve and inspect valve operation. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [LF, L3].) • Is PCV valve operation normal?	Yes	Replace the PCV valve, then go to Step 20.
No	Go to the next step.
18	INSPECT OPERATION OF EGR VALVE • Remove the EGR valve. • Visually inspect the EGR valve for stuck to open. • Is EGR valve stuck to open?	Yes	Repair or replace the EGR valve, then go to Step 20.
No	Go to the next step.
19	INSPECT SEALING OF ENGINE COOLANT PASSAGE • Perform “ENGINE COOLANT LEAKAGE INSPECTION.” (See ENGINE COOLANT LEAKAGE INSPECTION [LF, L3].) • Is there any malfunction?	Yes	Repair or replace malfunctioning part according to inspection results. Then go to the next step.
No	Go to the next step.
20	VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED • Make sure to reconnect all disconnected connectors. • Turn the ignition switch to the ON position (Engine off). • Clear the DTC from the memory using the M-MDS. • Perform the KOER self-test or the A/F sensor heater, HO2S heater, A/F sensor, HO2S, and TWC Repair Verification Drive Mode. (See OBD DRIVE MODE [LF ATX (FN4A-EL), L3 ATX].) • Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [LF, L3].)
No	Go to the next step.
21	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [LF ATX (FN4A-EL), L3 ATX].) • Are any DTCs present?	Yes	Go to the applicable DTC troubleshooting. (See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)
No	Troubleshooting completed.

STEP

INSPECTION

ACTION

VERIFY FREEZE FRAME DATA HAVE BEEN RECORDED

• Have FREEZE FRAME DATA been recorded?

Yes

Go to the next step.

Record the FREEZE FRAME DATA on repair order, then go to the next step.

VERIFY RELATED SERVICE INFORMATION AVAILABILITY

• Verify related Service Information availability.

• Is any related Service Information available?

Yes

Perform repair or diagnosis according to the available Service Information.

• If the vehicle is not repaired, go to the next step.

Go to the next step.

VERIFY RELATED PENDING CODE OR STORED DTC

• 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 [LF ATX (FN4A-EL), L3 ATX].)

Go to the next step.

VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON/IDLE)

• Access APP1, APP2, ECT, IAT, MAF, RPM, TP, and VSS PIDs using M-MDS.

(See PCM INSPECTION [LF, L3].)

• 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 suspected circuit and/or part according to inspection results.

(See PCM INSPECTION [LF, L3].)

Then go to Step 20.

Go to the next step.

VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION

• Inspect the 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 [LF, L3].)

Then go to Step 20.

Go to the next step.

INSPECT CMP SENSOR

• Inspect CMP sensor.

(See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [LF, L3].)

• Is CMP sensor normal?

Yes

Go to the next step.

Inspect installation condition and damages on timing chain and gears, repair the malfunctioning part.

• If it is normal, replace the CMP sensor.

Then go to Step 20.

VERIFY CKP SENSOR INSTALLATION CONDITION

• Inspect for CKP sensor looseness.

• Is CKP sensor loosen?

Yes

Retighten the CKP sensor, then go to Step.

Go to the next step.

INSPECT IGNITION COIL HARNESSES

• Inspect the ignition coil related harness condition (intermittent open or short) for all cylinders.

• Are harness conditions normal?

Yes

Go to the next step.

Repair suspected wiring harnesses, then go to Step 20.

INSPECT IGNITION SYSTEM OPERATION

• Carry out spark test.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF, L3])

• Is strong blue spark visible at each cylinder?

Yes

Go to the next step.

Repair or replace malfunctioning part according to spark test result.

Then go to Step 20.

INSPECT MAF PID

• Start the engine.

• Access MAF PID using the M-MDS.

• Race the engine and verify that MAF PID changes quickly according to change in the engine speed.

• Is MAF PID response normal?

Yes

Go to the next step.

Replace the MAF sensor, then go to Step 20.

INSPECT EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM

• Inspect for air leakage at following:

― Between the 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 20.

Go to the next step.

INSPECT FUEL LINE PRESSURE

• Inspect fuel line pressure.

(See FUEL LINE PRESSURE INSPECTION [LF, L3].)

• Is fuel line pressure normal?

Yes

Go to Step 14.

If the fuel line pressure is too low, go to the next step.

If the fuel line pressure is excess high, replace the fuel pump unit,

then go to Step 20.

INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE

• Visually inspect fuel line for fuel leakage.

• Is there any fuel leakage?

Yes

Replace suspected fuel line, then go to Step 20.

Inspect fuel filters for following:

• Foreign materials or stain inside fuel filter (low-pressure side)

Perform following actions depend on the result above.

• If foreign materials or stain is found inside fuel filter (low-pressure side), clean the fuel tank and filter (low-pressure side).

• If normal, replace the fuel pump unit.

Then, go to Step 20.

INSPECT ENGINE COMPRESSION

• Inspect engine compression.

(See COMPRESSION INSPECTION [LF, L3].)

• Is it normal?

Yes

Go to the next step.

Perform engine overhaul for repairs, then go to Step 20.

INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION

• Inspect variable valve timing control system operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [LF, L3])

• Does variable valve timing control system work properly?

Yes

Go to the next step.

Repair or replace malfunctioning part according to variable valve timing control system inspection results, then go to Step 20.

INSPECT OPERATION OF PURGE CONTROL SOLENOID VALVE

• Turn the ignition switch off.

• Connect the 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 the M-MDS.

• 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 while solenoid is turned ON.

• Is purge control solenoid valve operation normal?

Yes

Go to the next step.

Replace the purge control solenoid valve, then go to Step 20.

INSPECT PCV VALVE OPERATION

• Turn the ignition switch off.

• Remove PCV valve and inspect valve operation.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [LF, L3].)

• Is PCV valve operation normal?

Yes

Replace the PCV valve, then go to Step 20.

Go to the next step.

INSPECT OPERATION OF EGR VALVE

• Remove the EGR valve.

• Visually inspect the EGR valve for stuck to open.

• Is EGR valve stuck to open?

Yes

Repair or replace the EGR valve, then go to Step 20.

Go to the next step.

INSPECT SEALING OF ENGINE COOLANT PASSAGE

• Perform “ENGINE COOLANT LEAKAGE INSPECTION.”

(See ENGINE COOLANT LEAKAGE INSPECTION [LF, L3].)

• Is there any malfunction?

Yes

Repair or replace malfunctioning part according to inspection results.

Then go to the next step.

Go to the next step.

VERIFY TROUBLESHOOTING OF MISFIRE DTC COMPLETED

• Make sure to reconnect all disconnected connectors.

• Turn the ignition switch to the ON position (Engine off).

• Clear the DTC from the memory using the M-MDS.

• Perform the KOER self-test or the A/F sensor heater, HO2S heater, A/F sensor, HO2S, and TWC Repair Verification Drive Mode. (See OBD DRIVE MODE [LF ATX (FN4A-EL), L3 ATX].)

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [LF, L3].)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE [LF ATX (FN4A-EL), L3 ATX].)

• Are any DTCs present?

Yes

Go to the applicable DTC troubleshooting.

(See DTC TABLE [LF ATX (FN4A-EL), L3 ATX].)

Troubleshooting completed.