DTC P0300 [MZI-3.7]

DTC P0300	Random misfire detected
DETECTION CONDITION	• The PCM monitors the crankshaft position sensor input signal interval time. The PCM calculates the change of the interval time for each cylinder. If the change of interval time exceeds the pre-programmed criteria, the PCM detects a misfire in the corresponding cylinder. When the engine is running, the PCM counts the number of misfires that occurred at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates the misfire ratio for each crankshaft revolution. If the ratio exceeds the pre-programmed criteria, the PCM determines that a misfire, which can damage the catalytic converter or affect emission performance, has occurred.
POSSIBLE CAUSE	• Erratic signal to PCM ― APP sensor signal malfunction ― ECT sensor signal malfunction ― IAT sensor signal malfunction ― MAF sensor signal malfunction ― CKP sensor signal malfunction ― TP sensor signal malfunction ― VSS signal malfunction ― Related connector and terminal malfunction ― Related wiring harness malfunction • CMP sensor malfunction • CKP sensor malfunction • Ignition coil malfunction • Ignition system malfunction • Excess air suction in intake air system (between MAF/IAT sensor and dynamic chamber) • Vacuum hoses damages or improper connection • MAF sensor contamination • Fuel pump malfunction • Fuel pressure regulator malfunction • Fuel line clogged • Fuel filter clogged • Fuel leakage in fuel line • Fuel runout • Insufficient compression • Variable valve timing control system improper operation • Purge solenoid valve malfunction • PCV valve malfunction • Engine malfunction (Leakage engine coolant) • Poor quality fuel • PCM malfunction

DTC P0300

Random misfire detected

DETECTION CONDITION

• The PCM monitors the crankshaft position sensor input signal interval time. The PCM calculates the change of the interval time for each cylinder. If the change of interval time exceeds the pre-programmed criteria, the PCM detects a misfire in the corresponding cylinder. When the engine is running, the PCM counts the number of misfires that occurred at 200 crankshaft revolutions and 1,000 crankshaft revolutions and calculates the misfire ratio for each crankshaft revolution. If the ratio exceeds the pre-programmed criteria, the PCM determines that a misfire, which can damage the catalytic converter or affect emission performance, has occurred.

POSSIBLE CAUSE

• Erratic signal to PCM

― APP sensor signal malfunction

― ECT sensor signal malfunction

― IAT sensor signal malfunction

― MAF sensor signal malfunction

― CKP sensor signal malfunction

― TP sensor signal malfunction

― VSS signal malfunction

― Related connector and terminal malfunction

― Related wiring harness malfunction

• CMP sensor malfunction

• CKP sensor malfunction

• Ignition coil malfunction

• Ignition system malfunction

• Excess air suction in intake air system (between MAF/IAT sensor and dynamic chamber)

• Vacuum hoses damages or improper connection

• MAF sensor contamination

• Fuel pump malfunction

• Fuel pressure regulator malfunction

• Fuel line clogged

• Fuel filter clogged

• Fuel leakage in fuel line

• Fuel runout

• Insufficient compression

• Variable valve timing control system improper operation

• Purge solenoid valve malfunction

• PCV valve malfunction

• Engine malfunction (Leakage engine coolant)

• Poor quality fuel

• PCM malfunction

STEP	INSPECTION	ACTION
1	VERIFY FREEZE FRAME DATA HAS BEEN RECORDED • Has FREEZE FRAME DATA been recorded?	Yes	Go to the next step.
No	Record FREEZE FRAME DATA on the 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 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 [MZI-3.7].)
No	Go to the next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS (KEY TO ON/IDLE) • Access APP1, APP2, APP3, ECT, IAT, MAF, RPM, TP_REL and VSS PIDs using the M-MDS. (See PCM INSPECTION [MZI-3.7].) • Is there any signal that is far out of specification when the ignition switch is in the ON position and engine runs at idle?	Yes	Inspect the suspected circuit or part or both according to inspection results. (See PCM INSPECTION [MZI-3.7].) Then go to Step 18.
No	Go to the next step.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION • Inspect the same PIDs as in Step 4 when simulating the FREEZE FRAME DATA condition. • Is there any signal which causes drastic changes?	Yes	Inspect the suspected circuit or part or both according to inspection results. (See PCM INSPECTION [MZI-3.7].) Then go to Step 18.
No	Go to the next step.
6	INSPECT CMP SENSOR • Inspect the CMP sensor. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [MZI-3.7].) • Is there any malfunction?	Yes	Inspect the installation condition for damage to the timing chain and gears, and repair malfunctioning parts. • If it is normal, replace CMP sensor. (See CAMSHAFT POSITION (CMP) SENSOR REMOVAL/INSTALLATION [MZI-3.7].) Then go to Step 18.
No	Go to the next step.
7	VERIFY CKP SENSOR INSTALLATION CONDITION • Inspect for CKP sensor looseness. • Is the CKP sensor loose?	Yes	Retighten the CKP sensor, then go to Step 18. (See CRANKSHAFT POSITION (CKP) SENSOR REMOVAL/INSTALLATION [MZI-3.7].)
No	Go to the next step.
8	INSPECT IGNITION SYSTEM OPERATION • Perform the spark test. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) • Are the results of the spark test normal?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part according to the spark test results, then go to Step 18.
9	INSPECT MAF PID • Start the engine. • Access the MAF PID using the M-MDS. • Verify that the MAF PID changes quickly according to the engine speed when the engine is raced. • Is the MAF PID response normal?	Yes	Go to Step 11.
No	Go to the next step.
10	INSPECT FOR EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM • Inspect for air leakage at the following: ― Between the MAF/IAT sensor and the throttle body ― Between the throttle body and the dynamic chamber • Is there any malfunction?	Yes	Repair or replace the suspected part, then go to Step 18.
No	Replace the MAF/IAT sensor, then go to Step 18. (See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [MZI-3.7].)
11	INSPECT FUEL LINE PRESSURE • Turn the ignition switch off. • Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [MZI-3.7].) • Is there any malfunction?	Yes	If the fuel line pressure is too low, go to the next step. If the fuel line pressure is excessively high, check as follows: • Fuel pump maximum pressure • Fuel return line for clogging ― If all of the above are normal, replace the pressure regulator. (See PRESSURE REGULATOR INSPECTION [MZI-3.7].) Then go to Step 18.
No	Go to Step 13.
12	INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE • Visually inspect the fuel line for any leakage. • Is any fuel leakage found?	Yes	Replace suspected fuel line, then go to Step 18.
No	Inspect the low-pressure side fuel filter for the following: • Foreign material or staining inside the fuel filter Perform the following actions as a result: • If foreign material or staining is found inside the fuel filter (low-pressure side), clean the fuel tank and filter. • If normal, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].) Then, go to Step 18.
13	INSPECT ENGINE COMPRESSION • Inspect the engine compression. (See COMPRESSION INSPECTION [MZI-3.7].) • Is it normal?	Yes	Go to the next step.
No	Perform an engine overhaul for repairs, then go to Step 18.
14	INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION • Inspect the variable valve timing control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) • Does the variable timing control system work properly?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part according to the variable valve timing control system inspection results, then go to Step 18.
15	INSPECT OPERATION OF PURGE SOLENOID VALVE • Inspect the purge control system operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].) • Does the purge control system work properly?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part according to the purge control system inspection results, then go to Step 18.
16	INSPECT PCV VALVE OPERATION • Turn the ignition switch off. • Remove the PCV valve and check the valve operation. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZI-3.7].) • Is the PCV valve operation normal?	Yes	Go to the next step.
No	Replace the PCV valve, then go to Step 18.
17	INSPECT SEALING OF ENGINE COOLANT PASSAGE Warning • Never remove the cooling system cap or loosen the radiator drain plug while the engine is running, or when the engine and radiator are hot. Scalding engine coolant and steam may shoot out and cause serious injury. It may also damage the engine and cooling system. • Turn off the engine and wait until it is cool. Even then, be very careful when removing the cap. Wrap a thick cloth around it and slowly turn it counterclockwise to the first stop. Step back while the pressure escapes • When you are sure all the pressure is gone, press down on the cap using the cloth, turn it, and remove it. • Remove the radiator cap. • Implement the procedure to bleed air from the engine coolant, then run the engine at idle • Are there any small bubbles which make the engine coolant white at the filling opening? Note • Large bubbles are normal since they are remaining air coming from the engine coolant passage.	Yes	Air penetrates due to poor sealing of the head gasket or other areas between the combustion chamber and the engine coolant passage. Repair or replace malfunctioning parts, then go to the next step.
No	Go to the next step.
18	VERIFY TROUBLESHOOTING OF DTC P0300 HAS BEEN COMPLETED • Verify that all disconnected connectors are reconnected. • Clear the DTC from the PCM memory using the M-MDS. • Perform the KOER SELF TEST using the M-MDS. (See KOEO/KOER SELF TEST [MZI-3.7].) • Is the PENDING CODE for this DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [MZI-3.7].)
No	Go to the next step.
19	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE [MZI-3.7].) • Are any DTC present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [MZI-3.7].)
No	Troubleshooting completed.

STEP

INSPECTION

ACTION

VERIFY FREEZE FRAME DATA HAS BEEN RECORDED

• Has FREEZE FRAME DATA been recorded?

Yes

Go to the next step.

Record FREEZE FRAME DATA on the 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 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 [MZI-3.7].)

Go to the next step.

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

• Access APP1, APP2, APP3, ECT, IAT, MAF, RPM, TP_REL and VSS PIDs using the M-MDS.

(See PCM INSPECTION [MZI-3.7].)

• Is there any signal that is far out of specification when the ignition switch is in the ON position and engine runs at idle?

Yes

Inspect the suspected circuit or part or both according to inspection results.

(See PCM INSPECTION [MZI-3.7].)

Then go to Step 18.

Go to the next step.

VERIFY CURRENT INPUT SIGNAL STATUS UNDER TROUBLE CONDITION

• Inspect the same PIDs as in Step 4 when simulating the FREEZE FRAME DATA condition.

• Is there any signal which causes drastic changes?

Yes

Inspect the suspected circuit or part or both according to inspection results.

(See PCM INSPECTION [MZI-3.7].)

Then go to Step 18.

Go to the next step.

INSPECT CMP SENSOR

• Inspect the CMP sensor.

(See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [MZI-3.7].)

• Is there any malfunction?

Yes

Inspect the installation condition for damage to the timing chain and gears, and repair malfunctioning parts.

• If it is normal, replace CMP sensor.

(See CAMSHAFT POSITION (CMP) SENSOR REMOVAL/INSTALLATION [MZI-3.7].)

Then go to Step 18.

Go to the next step.

VERIFY CKP SENSOR INSTALLATION CONDITION

• Inspect for CKP sensor looseness.

• Is the CKP sensor loose?

Yes

Retighten the CKP sensor, then go to Step 18.

(See CRANKSHAFT POSITION (CKP) SENSOR REMOVAL/INSTALLATION [MZI-3.7].)

Go to the next step.

INSPECT IGNITION SYSTEM OPERATION

• Perform the spark test.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)

• Are the results of the spark test normal?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the spark test results, then go to Step 18.

INSPECT MAF PID

• Start the engine.

• Access the MAF PID using the M-MDS.

• Verify that the MAF PID changes quickly according to the engine speed when the engine is raced.

• Is the MAF PID response normal?

Yes

Go to Step 11.

Go to the next step.

INSPECT FOR EXCESSIVE AIR SUCTION IN INTAKE AIR SYSTEM

• Inspect for air leakage at the following:

― Between the MAF/IAT sensor and the throttle body

― Between the throttle body and the dynamic chamber

• Is there any malfunction?

Yes

Repair or replace the suspected part, then go to Step 18.

Replace the MAF/IAT sensor, then go to Step 18.

(See INTAKE-AIR SYSTEM REMOVAL/INSTALLATION [MZI-3.7].)

INSPECT FUEL LINE PRESSURE

• Turn the ignition switch off.

• Inspect the fuel line pressure.

(See FUEL LINE PRESSURE INSPECTION [MZI-3.7].)

• Is there any malfunction?

Yes

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

If the fuel line pressure is excessively high, check as follows:

• Fuel pump maximum pressure

• Fuel return line for clogging

― If all of the above are normal, replace the pressure regulator.

(See PRESSURE REGULATOR INSPECTION [MZI-3.7].)

Then go to Step 18.

Go to Step 13.

INSPECT FUEL LINE FROM FUEL PUMP TO FUEL DELIVERY PIPE

• Visually inspect the fuel line for any leakage.

• Is any fuel leakage found?

Yes

Replace suspected fuel line, then go to Step 18.

Inspect the low-pressure side fuel filter for the following:

• Foreign material or staining inside the fuel filter

Perform the following actions as a result:

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

• If normal, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [MZI-3.7].)

Then, go to Step 18.

INSPECT ENGINE COMPRESSION

• Inspect the engine compression.

(See COMPRESSION INSPECTION [MZI-3.7].)

• Is it normal?

Yes

Go to the next step.

Perform an engine overhaul for repairs, then go to Step 18.

INSPECT VARIABLE VALVE TIMING CONTROL SYSTEM OPERATION

• Inspect the variable valve timing control system operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)

• Does the variable timing control system work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the variable valve timing control system inspection results, then go to Step 18.

INSPECT OPERATION OF PURGE SOLENOID VALVE

• Inspect the purge control system operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)

• Does the purge control system work properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to the purge control system inspection results, then go to Step 18.

INSPECT PCV VALVE OPERATION

• Turn the ignition switch off.

• Remove the PCV valve and check the valve operation.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [MZI-3.7].)

• Is the PCV valve operation normal?

Yes

Go to the next step.

Replace the PCV valve, then go to Step 18.

INSPECT SEALING OF ENGINE COOLANT PASSAGE

Warning

• Never remove the cooling system cap or loosen the radiator drain plug while the engine is running, or when the engine and radiator are hot. Scalding engine coolant and steam may shoot out and cause serious injury. It may also damage the engine and cooling system.

• Turn off the engine and wait until it is cool. Even then, be very careful when removing the cap. Wrap a thick cloth around it and slowly turn it counterclockwise to the first stop. Step back while the pressure escapes

• When you are sure all the pressure is gone, press down on the cap using the cloth, turn it, and remove it.

• Remove the radiator cap.

• Implement the procedure to bleed air from the engine coolant, then run the engine at idle

• Are there any small bubbles which make the engine coolant white at the filling opening?

Note

• Large bubbles are normal since they are remaining air coming from the engine coolant passage.

Yes

Air penetrates due to poor sealing of the head gasket or other areas between the combustion chamber and the engine coolant passage. Repair or replace malfunctioning parts, then go to the next step.

Go to the next step.

VERIFY TROUBLESHOOTING OF DTC P0300 HAS BEEN COMPLETED

• Verify that all disconnected connectors are reconnected.

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

• Perform the KOER SELF TEST using the M-MDS.

(See KOEO/KOER SELF TEST [MZI-3.7].)

• Is the PENDING CODE for this DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION [MZI-3.7].)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE [MZI-3.7].)

• Are any DTC present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE [MZI-3.7].)

Troubleshooting completed.