DTC P0300 [LF]: Notes

DTC P0300 (LF) DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0300	Random misfire detected
DETECTION CONDITION	The PCM monitors the 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 the first drive cycle. 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 IAT sensor signal malfunction MAF sensor signal malfunction CKP sensor signal malfunction TP sensor signal malfunction VSS signal malfunction CMP sensor malfunction CKP sensor looseness Ignition system malfunction Ignition coil related wiring harness malfunction Ignition coil malfunction Spark plug malfunction Excess air suction in intake air system (between MAF sensor and intake manifold) Vacuum hoses damages or improper connection Pipe malfunction MAF sensor contamination Improper operation of variable valve timing control system Improper operation of purge solenoid valve Fuel supply system malfunction or improper fuel line pressure Fuel pressure regulator (built-in fuel pump unit) malfunction Fuel leakage in fuel line Fuel line clogged Fuel filter clogged Fuel pump unit malfunction Fuel runout Engine internal malfunction Engine coolant leakage to combustion chamber Insufficient compression EGR valve malfunction PCV valve malfunction Poor quality fuel PCM malfunction

DTC P0300

Random misfire detected

DETECTION CONDITION

The PCM monitors the 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 the first drive cycle.
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
- IAT sensor signal malfunction
- MAF sensor signal malfunction
- CKP sensor signal malfunction
- TP sensor signal malfunction
- VSS signal malfunction
CMP sensor malfunction
CKP sensor looseness
Ignition system malfunction
- Ignition coil related wiring harness malfunction
- Ignition coil malfunction
- Spark plug malfunction
Excess air suction in intake air system (between MAF sensor and intake manifold)
- Vacuum hoses damages or improper connection
- Pipe malfunction
MAF sensor contamination
Improper operation of variable valve timing control system
Improper operation of purge solenoid valve
Fuel supply system malfunction or improper fuel line pressure
- Fuel pressure regulator (built-in fuel pump unit) malfunction
- Fuel leakage in fuel line
- Fuel line clogged
- Fuel filter clogged
- Fuel pump unit malfunction
- Fuel runout
Engine internal malfunction
- Engine coolant leakage to combustion chamber
- Insufficient compression
EGR valve malfunction
PCV valve malfunction
Poor quality fuel
PCM malfunction