DTC P0300

DTC P0300	Random misfire detected
DETECTION CONDITION	The PCM monitors the 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 the 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 (Mode 2/Mode 12) is available. The DTC is stored in the PCM memory.
POSSIBLE CAUSE	Erratic signal to PCM APP sensor signal malfunction ECT sensor signal malfunction MAF sensor signal malfunction TP sensor signal malfunction VSS signal malfunction Eccentric shaft position sensor malfunction Ignition system malfunction High-tension lead malfunction Incorrect power supply to ignition coif Ignition coil malfunction Spark plug malfunction Excess air suction in intake-air system MAF sensor malfunction Fuel line pressure malfunction Leakage fuel Fuel pump unit malfunction Pressure regulator (built-in fuel pump unit) malfunction Insufficient compression Metering oil pump malfunction Engine oil condition malfunction Increased oil pressure Oil passage malfunction Engine malfunction Purge control system malfunction Leakage engine coolant PCM malfunction

Random misfire detected

DETECTION CONDITION

The PCM monitors the 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 the 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 (Mode 2/Mode 12) is available.
The DTC is stored in the PCM memory.

POSSIBLE CAUSE

Erratic signal to PCM
- APP sensor signal malfunction
- ECT sensor signal malfunction
- MAF sensor signal malfunction
- TP sensor signal malfunction
- VSS signal malfunction
Eccentric shaft position sensor malfunction
Ignition system malfunction
- High-tension lead malfunction
- Incorrect power supply to ignition coif
- Ignition coil malfunction
Spark plug malfunction
Excess air suction in intake-air system
MAF sensor malfunction
Fuel line pressure malfunction
- Leakage fuel
- Fuel pump unit malfunction
- Pressure regulator (built-in fuel pump unit) malfunction
Insufficient compression
- Metering oil pump malfunction
- Engine oil condition malfunction
- Increased oil pressure
- Oil passage malfunction
- Engine malfunction
Purge control system malfunction
Leakage engine coolant
PCM malfunction

DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	VERIFY FREEZE FRAME DATA (MODE 12) AND DIAGNOSTIC MONITORING TEST RESULTS HAVE BEEN RECORDED Have the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS (misfire related) been recorded?	Yes	Go to the next step.
1		No	Record the FREEZE FRAME DATA (Mode 12) and DIAGNOSTIC MONITORING TEST RESULTS on the repair order, then go to the next step.
2	VERIFY RELATED REPAIR INFORMATION AVAILABILITY Verify related Service Bulletins and/or on-line 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.
2		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 ).
3		No	Go to the next step.
4	VERIFY CURRENT INPUT SIGNAL STATUS Access the following PIDs using the M-MDS: (See ON-BOARD DIAGNOSTIC TEST ). APP ECT MAF TP REL VSS Are the PIDs normal? (See PCM INSPECTION ).	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning part according to the inspection results, then go to Step 23.
5	VERIFY CURRENT INPUT SIGNAL STATUS UNDER FREEZE FRAME DATA (MODE 2) CONDITION CAUTION: While performing this step with vehicle driving, always operate the vehicle in a safe and lawful manner. When the M-MDS is used to observe monitor system status while driving, be sure to have another technician with you, or record the data in the M-MDS using the PID/DATA MONITOR AND RECORD function and inspect later. Access the following PIDs using the M-MDS under the FREEZE FRAME DATA (Mode 2) condition: (See ON-BOARD DIAGNOSTIC TEST ). APP ECT MAF TP REL VSS Are the PIDs normal? (See PCM INSPECTION ).	Yes	Go to the next step.
5		No	Repair or replace the malfunctioning part according to the inspection results, then go to Step 23.
6	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 ).
6		No	Go to the next step.
7	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 high-tension leads show blinking condition?	Yes	Go to Step 11.
7		No	Go to the next step.
8	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 ).
8		No	Go to the next step.
9	INSPECT IGNITION COIL POWER CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND Turn the ignition switch to the ON position (engine off). Measure the voltage between ignition coil terminal C (wiring harness-side) and body ground. Is the voltage B+?	Yes	Go to the next step.
9		No	Repair or replace the wiring harness for a possible open circuit or short to ground, then go to Step 23.
10	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 ).
10		No	Inspect for open circuit in wiring harness between ignition coil terminal B and ground. Repair or replace the wiring harness for a possible open circuit, then go to Step 23.
11	INSPECT SPARK PLUG Inspect the spark plug. (See SPARK PLUG INSPECTION ). Is there any malfunction?	Yes	Replace the spark plug, then go to Step 23. (See SPARK PLUG REMOVAL/INSTALLATION ).
11		No	Go to the next step.
12	VERIFY CURRENT INPUT SIGNAL STATUS OF MAF SENSOR Start the engine. Access the MAF PID using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST ). Verify that the MAF PID changes quickly according to the RPM when the engine is raced. Is the PID normal? (See PCM INSPECTION ).	Yes	Go to Step 14.
12		No	Go to the next step.
13	INSPECT INTAKE-AIR SYSTEM FOR EXCESSIVE AIR SUCTION Visually inspect for looseness, cracks or damaged hoses in intake-air system. Is there any malfunction?	Yes	Repair or replace the malfunctioning part according to the inspection results, then go to Step 23.
13		No	Replace the MAF/IAT sensor, then go to Step 23. (See MASS AIR FLOW (MAF)/INTAKE AIR TEMPERATURE (IAT) SENSOR REMOVAL/INSTALLATION ).
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 ).
14		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 according to the inspection results, then go to Step 23.
15		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.
16		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.
17		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.
18		No	Replace the engine oil. 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.
19		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 for leakage or clogging in the engine oil passage. Repair or replace the malfunctioning part according to the inspection results. Overhaul or replace the engine, then go to Step 23.
20		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.
21		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.
22		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 M-MDS. (See AFTER REPAIR PROCEDURE ). Start the engine and warm it up completely. Perform the Pending Trouble Code Access Procedure. (See ON-BOARD DIAGNOSTIC TEST ). Is the PENDING CODE same as the DTC present?	Yes	Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION ).
23		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 ).
24		No	DTC troubleshooting completed.