DTC P0300

DTC P0300	Random misfire detected
DETECTION CONDITION	• The PCM monitors eccentric shaft position sensor input signal interval time. The PCM calculates the change of the interval time for each rotor. If the change of interval time exceeds the preprogrammed criteria, the PCM detects a misfire in the corresponding rotor. While the engine is running, the PCM counts the number of misfires that occurred at 200 eccentric shaft revolutions and 1,000 eccentric shaft revolutions and calculates misfire ratio for each eccentric shaft revolution. If the ratio exceeds the preprogrammed criteria, the PCM determines that a misfire, which can damage the 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 the first drive cycle. Therefore, PENDING CODE is not available while the MIL flashes. • PENDING CODE is available if the PCM detects the misfire which affects emission performance during the first drive cycle. • FREEZE FRAME DATA is available. • The DTC is stored in the PCM memory.
POSSIBLE CAUSE	• When the eccentric shaft position plate or the engine was replaced, the learning value for misfire determination was not initialized. • Eccentric shaft position sensor malfunction • Ignition system malfunction ― High-tension lead malfunction ― Incorrect power supply to ignition coil ― Ignition coil malfunction • MAF sensor malfunction • Excess air suction in intake-air system • Fuel line pressure malfunction • Fuel pump unit malfunction • Leakage fuel • Insufficient compression ― Metering oil pump malfunction ― Engine oil condition malfunction ― Rised oil pressure ― Oil passage malfunction ― Engine malfunction • ECT sensor malfunction • Purge control system malfunction • Leakage engine coolant • PCM malfunction

Random misfire detected

DETECTION CONDITION

• The PCM monitors eccentric shaft position sensor input signal interval time. The PCM calculates the change of the interval time for each rotor. If the change of interval time exceeds the preprogrammed criteria, the PCM detects a misfire in the corresponding rotor. While the engine is running, the PCM counts the number of misfires that occurred at 200 eccentric shaft revolutions and 1,000 eccentric shaft revolutions and calculates misfire ratio for each eccentric shaft revolution. If the ratio exceeds the preprogrammed criteria, the PCM determines that a misfire, which can damage the 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 the first drive cycle. Therefore, PENDING CODE is not available while the MIL flashes.

• PENDING CODE is available if the PCM detects the misfire which affects emission performance during the first drive cycle.

• FREEZE FRAME DATA is available.

• The DTC is stored in the PCM memory.

POSSIBLE CAUSE

• When the eccentric shaft position plate or the engine was replaced, the learning value for misfire determination was not initialized.

• Eccentric shaft position sensor malfunction

• Ignition system malfunction

― High-tension lead malfunction

― Incorrect power supply to ignition coil

― Ignition coil malfunction

• MAF sensor malfunction

• Excess air suction in intake-air system

• Fuel line pressure malfunction

• Fuel pump unit malfunction

• Leakage fuel

• Insufficient compression

― Metering oil pump malfunction

― Engine oil condition malfunction

― Rised oil pressure

― Oil passage malfunction

― Engine malfunction

• ECT sensor malfunction

• Purge control system malfunction

• Leakage engine coolant

• 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 the FREEZE FRAME DATA on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY • Verify related service 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.
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 the related PENDING CODE or stored DTCs. • Are other DTCs present?	Yes	Go to the appropriate DTC inspection. (See DTC TABLE.)
No	Go to the next step.
4	PERFORM INITIALIZATION OF THE LEARNING VALUE FOR MISFIRE DETERMINATION • Perform initialization of the learning value for misfire determination Note • The learning value for misfire determination by the PCM can be initialized by performing the following procedure. • Pump the brake pedal 20 times within 8 s after the ignition switch is turn to the ON position (engine off). • Clear the DTC from the PCM memory using the WDS or equivlent. • Start the engine and warm it up completely. • Is the PENDING CODE same as the DTC present?	Yes	Go to the next step.
No	Go to Step 24.
5	VERIFY CURRENT INPUT SIGNAL STATUS • Connect the WDS or equivalent to the DLC-2. • Verify the following PIDs. (See PCM INSPECTION.) ― APP ― ECT ― MAF ― TP ― VSS • Are the PIDs normal?	Yes	Go to the next step.
No	Inspect the malfunctioning part according to the inspection results. Then go to Step 23.
6	VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA CONDITION • Connect the WDS or equivalent to the DLC-2. • Verify the following PIDs under the FREEZE FRAME DATA condition. (See PCM INSPECTION.) ― APP ― ECT ― MAF ― TP ― VSS • Are the PIDs normal?	Yes	Go to the next step.
No	Inspect the malfunctioning part according to the inspection results. Then go to Step 23.
7	INSPECT ECCENTRIC SHAFT POSITION SENSOR • Inspect the eccentric shaft position sensor. (See ECCENTRIC SHAFT POSITION SENSOR INSPECTION.) • Is there any malfunction?	Yes	Replace the eccentric shaft position sensor, then go to Step 23. (See ECCENTRIC SHAFT POSITION SENSOR REMOVAL/INSTALLATION.)
No	Go to the next step.
8	INSPECT IGNITION COIL OPERATION AND HIGH-TENSION LEAD WITH TIMING LIGHT • Inspect the blinking condition on each high-tension leads using timing light at idle. • Do all the high-tension leads show blinking condition?	Yes	Go to Step 12.
No	Go to the next step.
9	INSPECT HIGH-TENSION LEAD OF NO BLINKING HIGH-TENSION LEAD • Inspect the high-tension leads. (See HIGH‐TENSION LEAD INSPECTION.) • Is there any malfunction?	Yes	Replace the malfunctioning high-tension lead, then go to Step 23. (See HIGH‐TENSION LEAD REMOVAL/INSTALLATION.)
No	Go to the next step.
10	INSPECT IGNITION COIL POWER CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GND • Turn the ignition switch to the ON position (Engine off). • Measure the voltage between ignition coil terminal C (wiring harness-side) and body GND. • Is the voltage B+?	Yes	Go to the next step.
No	Repair or replace the wiring harness for a possible open circuit or short to GND, then go to Step 23.
11	INSPECT IGNITION COIL • Inspect the ignition coil. (See IGNITION COIL INSPECTION.) • Is there any malfunction?	Yes	Replace the ignition coil, then go to Step 23. (See IGNITION COIL REMOVAL/INSTALLATION.)
No	Go to the next step.
12	VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR • Connect the WDS or equivalent to the DLC-2. • Start the engine. • Access the MAF PID. • Verify that the MAF PID changes quickly according to race the engine RPM. • Is the PID normal?	Yes	Go to the next step.
No	Replace the MAF/IAT sensor, then go to Step 23. (See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION.)
13	INSPECT INTAKE-AIR SYSTEM FOR EXCESSIVE AIR SUCTION • Visually inspect for loosen, cracks or damages hoses in intake-air system. • Is there any malfunction?	Yes	Repair or replace the malfunctioning part, then go to Step 23.
No	Go to the next step.
14	INSPECT FUEL LINE PRESSURE • Perform the ”FUEL LINE PRESSURE INSPECTION”. (See FUEL LINE PRESSURE INSPECTION.) • Is there any malfunction?	Yes	• If the fuel line pressure is too low, go to the next step. • If the fuel line pressure is too high, replace the fuel pump unit, then go to Step 23. (See FUEL PUMP UNIT REMOVAL/INSTALLATION.)
No	Go to Step 16.
15	INSPECT FUEL SYSTEM FOR FUEL LEAKAGE • Visually inspect fuel leakage in the fuel system. • Is there fuel leakage?	Yes	Repair or replace the malfunctioning part, then go to Step 23.
No	Replace the fuel pump unit, then go to Step 23. (See FUEL PUMP UNIT REMOVAL/INSTALLATION.)
16	INSPECT ENGINE COMPRESSION • Inspect the engine compression. (See COMPRESSION INSPECTION.) • Is there any malfunction?	Yes	Go to the next step.
No	Go to Step 21.
17	INSPECT METERING OIL PUMP • Inspect the metering oil pump. (See METERING OIL PUMP INSPECTION.) • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Overhaul or replace the engine. Then go to Step 23.
No	Go to the next step.
18	INSPECT ENGINE OIL CONDITION • Inspect the engine oil condition. • Is the engine oil condition normal?	Yes	Go to the next step.
No	Replace the engine oil. Inspect the ECT sensor and related harnesses. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION.) Overhaul or replace the engine. Then go to Step 23.
19	INSPECT OIL PRESSURE • Inspect the oil pressure. (See OIL PRESSURE INSPECTION.) • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Overhaul or replace the engine. Then go to Step 23.
No	Go to the next step.
20	INSPECT OIL PASSAGE • Inspect the oil pipe between metering oil pump and metering oil nozzle. • Is there any malfunction?	Yes	Inspect and repair for leakage and/or clogged in oil passage at engine. Overhaul or replace the engine. Then go to Step 23.
No	Overhaul or replace the engine. Then go to Step 23.
21	INSPECT PURGE CONTROL SYSTEM OPERATION • Perform the “Purge Control System Inspection”. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION.) • Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results. Then go to Step 23.
No	Go to the next step.
22	INSPECT ENGINE COOLANT PASSAGE FOR ENGINE COOLANT LEAKAGE • Perform the “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 the next step.
No	Go to the next step.
23	VERIFY TROUBLESHOOTING OF DTC P0300 COMPLETED • Make sure to reconnect all disconnected connectors. • Clear the DTC from the PCM memory using the WDS or equivalent. • Start the engine and warm it up completely. • Is the PENDING CODE same as the DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION.)
No	Go to the next step.
24	VERIFY AFTER REPAIR PROCEDURE • Perform the “AFTER REPAIR PROCEDURE”. (See AFTER REPAIR PROCEDURE.) • Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE.)
No	DTC 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 the FREEZE FRAME DATA on the repair order, then go to the next step.

VERIFY RELATED REPAIR INFORMATION AVAILABILITY

• Verify related service 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.

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 the related PENDING CODE or stored DTCs.

• Are other DTCs present?

Yes

Go to the appropriate DTC inspection.

(See DTC TABLE.)

Go to the next step.

PERFORM INITIALIZATION OF THE LEARNING VALUE FOR MISFIRE DETERMINATION

• Perform initialization of the learning value for misfire determination

Note

• The learning value for misfire determination by the PCM can be initialized by performing the following procedure.

• Pump the brake pedal 20 times within 8 s after the ignition switch is turn to the ON position (engine off).

• Clear the DTC from the PCM memory using the WDS or equivlent.

• Start the engine and warm it up completely.

• Is the PENDING CODE same as the DTC present?

Yes

Go to the next step.

Go to Step 24.

VERIFY CURRENT INPUT SIGNAL STATUS

• Connect the WDS or equivalent to the DLC-2.

• Verify the following PIDs.

(See PCM INSPECTION.)

― APP

― ECT

― MAF

― TP

― VSS

• Are the PIDs normal?

Yes

Go to the next step.

Inspect the malfunctioning part according to the inspection results.

Then go to Step 23.

VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA CONDITION

• Connect the WDS or equivalent to the DLC-2.

• Verify the following PIDs under the FREEZE FRAME DATA condition.

(See PCM INSPECTION.)

― APP

― ECT

― MAF

― TP

― VSS

• Are the PIDs normal?

Yes

Go to the next step.

Inspect the malfunctioning part according to the inspection results.

Then go to Step 23.

INSPECT ECCENTRIC SHAFT POSITION SENSOR

• Inspect the eccentric shaft position sensor.

(See ECCENTRIC SHAFT POSITION SENSOR INSPECTION.)

• Is there any malfunction?

Yes

Replace the eccentric shaft position sensor, then go to Step 23.

(See ECCENTRIC SHAFT POSITION SENSOR REMOVAL/INSTALLATION.)

Go to the next step.

INSPECT IGNITION COIL OPERATION AND HIGH-TENSION LEAD WITH TIMING LIGHT

• Inspect the blinking condition on each high-tension leads using timing light at idle.

• Do all the high-tension leads show blinking condition?

Yes

Go to Step 12.

Go to the next step.

INSPECT HIGH-TENSION LEAD OF NO BLINKING HIGH-TENSION LEAD

• Inspect the high-tension leads.

(See HIGH‐TENSION LEAD INSPECTION.)

• Is there any malfunction?

Yes

Replace the malfunctioning high-tension lead, then go to Step 23.

(See HIGH‐TENSION LEAD REMOVAL/INSTALLATION.)

Go to the next step.

INSPECT IGNITION COIL POWER CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GND

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

• Measure the voltage between ignition coil terminal C (wiring harness-side) and body GND.

• Is the voltage B+?

Yes

Go to the next step.

Repair or replace the wiring harness for a possible open circuit or short to GND, then go to Step 23.

INSPECT IGNITION COIL

• Inspect the ignition coil.

(See IGNITION COIL INSPECTION.)

• Is there any malfunction?

Yes

Replace the ignition coil, then go to Step 23.

(See IGNITION COIL REMOVAL/INSTALLATION.)

Go to the next step.

VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR

• Connect the WDS or equivalent to the DLC-2.

• Start the engine.

• Access the MAF PID.

• Verify that the MAF PID changes quickly according to race the engine RPM.

• Is the PID normal?

Yes

Go to the next step.

Replace the MAF/IAT sensor, then go to Step 23.

(See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION.)

INSPECT INTAKE-AIR SYSTEM FOR EXCESSIVE AIR SUCTION

• Visually inspect for loosen, cracks or damages hoses in intake-air system.

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part, then go to Step 23.

Go to the next step.

INSPECT FUEL LINE PRESSURE

• Perform the ”FUEL LINE PRESSURE INSPECTION”.

(See FUEL LINE PRESSURE INSPECTION.)

• Is there any malfunction?

Yes

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

• If the fuel line pressure is too high, replace the fuel pump unit, then go to Step 23.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION.)

Go to Step 16.

INSPECT FUEL SYSTEM FOR FUEL LEAKAGE

• Visually inspect fuel leakage in the fuel system.

• Is there fuel leakage?

Yes

Repair or replace the malfunctioning part, then go to Step 23.

Replace the fuel pump unit, then go to Step 23.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION.)

INSPECT ENGINE COMPRESSION

• Inspect the engine compression.

(See COMPRESSION INSPECTION.)

• Is there any malfunction?

Yes

Go to the next step.

Go to Step 21.

INSPECT METERING OIL PUMP

• Inspect the metering oil pump.

(See METERING OIL PUMP INSPECTION.)

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results.

Overhaul or replace the engine.

Then go to Step 23.

Go to the next step.

INSPECT ENGINE OIL CONDITION

• Inspect the engine oil condition.

• Is the engine oil condition normal?

Yes

Go to the next step.

Replace the engine oil.

Inspect the ECT sensor and related harnesses.

(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION.)

Overhaul or replace the engine.

Then go to Step 23.

INSPECT OIL PRESSURE

• Inspect the oil pressure.

(See OIL PRESSURE INSPECTION.)

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results.

Overhaul or replace the engine.

Then go to Step 23.

Go to the next step.

INSPECT OIL PASSAGE

• Inspect the oil pipe between metering oil pump and metering oil nozzle.

• Is there any malfunction?

Yes

Inspect and repair for leakage and/or clogged in oil passage at engine.

Overhaul or replace the engine.

Then go to Step 23.

Overhaul or replace the engine.

Then go to Step 23.

INSPECT PURGE CONTROL SYSTEM OPERATION

• Perform the “Purge Control System Inspection”.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION.)

• Is there any malfunction?

Yes

Repair or replace the malfunctioning part according to the inspection results.

Then go to Step 23.

Go to the next step.

INSPECT ENGINE COOLANT PASSAGE FOR ENGINE COOLANT LEAKAGE

• Perform the “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 the next step.

Go to the next step.

VERIFY TROUBLESHOOTING OF DTC P0300 COMPLETED

• Make sure to reconnect all disconnected connectors.

• Clear the DTC from the PCM memory using the WDS or equivalent.

• Start the engine and warm it up completely.

• Is the PENDING CODE same as the DTC present?

Yes

Replace the PCM, then go to the next step.

(See PCM REMOVAL/INSTALLATION.)

Go to the next step.

VERIFY AFTER REPAIR PROCEDURE

• Perform the “AFTER REPAIR PROCEDURE”.

(See AFTER REPAIR PROCEDURE.)

• Are any DTCs present?

Yes

Go to the applicable DTC inspection.

(See DTC TABLE.)

DTC troubleshooting completed.