Specifications

ON-BOARD DIAGNOSTIC
F121
F
DTC P0300
A6E397001085W01
Diagnostic procedure
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 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, 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
• Variable valve timing control system improper (L3-VE)
STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA HAS BEEN
RECORDED
• Has FREEZE FRAME DATA been recorded?
Yes Go to next step.
No Record FREEZE FRAME DATA on repair order, then go to
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 next step.
No Go to next step.
3 VERIFY RELATED PENDING CODE OR
STORED DTCs
• Turn ignition key to OFF then ON (Engine
OFF).
• Verify related pending code or stored DTCs.
• Are other DTCs present?
Yes Go to appropriate DTC troubleshooting.
(See F67 DTC TABLE.)
No Go to next step.
4 VERIFY CURRENT INPUT SIGNAL STATUS
(IGNITION KEY TO ON/IDLE)
• Access BOO, ECT, IAT, MAF, RPM, TP, and
VSS PIDs using WDS or equivalent.
(See F45 PCM INSPECTION.)
• Is there any signal that is far out of
specification when ignition switch is ON and
engine runs at idle?
Yes Inspect suspected circuit and/or part according to
inspection results.
(See F45 PCM INSPECTION.)
Then go to Step 22.
No Go to next step.