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DTC P0300-00: Random Misfire Detected: Notes

DETECTION CONDITION AND POSSIBLE CAUSE

DTC P0300:00 Random misfire detected
DETECTION CONDITION 
  • The PCM monitors the CKP sensor input signal interval time. The PCM calculates the change of interval time for each cylinder. If the change of interval time exceeds the preprogrammed criteria, the PCM detects a misfire in the corresponding cylinder. While the engine is running, the PCM counts the number of misfires that occurred at 200 crankshaft revolutions  or 1000 crankshaft revolutions  and calculates the misfire ratio for each crankshaft 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 check engine light illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM.
  • The check engine light flashes if the PCM detects the misfire which can damage the catalytic converter during first drive cycle.
  • PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle.
  • FREEZE FRAME DATA (Mode 2)/Snapshot data is available.
  • The DTC is stored in the PCM memory.
FAIL-SAFE FUNCTION 
  • Limits the intake air amount.
POSSIBLE CAUSE 
  • Erratic signal to PCM
    • APP sensor signal malfunction
    • ECT sensor No.1 signal malfunction
    • IAT sensor No.1 signal malfunction
    • MAF sensor signal malfunction
    • CKP sensor signal malfunction
    • TP sensor signal malfunction
    • VSS signal malfunction
    • Related connector or terminals malfunction
    • Related wiring harness malfunction
  • Excessive air suction in intake air system (between MAF sensor and intake manifold)
  • MAF sensor malfunction
  • Improper operation of electric variable valve timing control system
    • Electric variable valve timing actuator malfunction
    • Electric variable valve timing motor malfunction
    • Electric variable valve timing driver malfunction
  • Improper operation of hydraulic variable valve timing control system
  • Improper operation of purge solenoid valve
  • Exhaust CMP sensor malfunction
  • CKP sensor loose
  • High-pressure side fuel delivery system malfunction
    • Fuel pressure sensor malfunction
    • Spill valve control solenoid valve control circuit malfunction (damage to driver in PCM caused by short circuit to ground system)
    • Spill valve control solenoid valve (built-into high pressure fuel pump) malfunction
    • Relief valve (built-into high pressure fuel pump) malfunction
    • High pressure fuel pump malfunction
  • Low-pressure side fuel delivery system malfunction
    • Fuel leakage in fuel line
    • Restricted fuel line
    • Restricted fuel filter
    • Fuel pressure regulator (built-into fuel pump unit) malfunction
    • Fuel pump unit malfunction
    • Fuel runout
  • Ignition system malfunction
    • Spark plug is wet or covered with carbon
    • Spark plug malfunction
    • Ignition coil malfunction
    • Ignition coil related wiring harness malfunction
  • Engine malfunction
    • Insufficient engine compression
    • Engine coolant leakage to combustion chamber
  • PCV valve malfunction
  • Poor quality fuel
  • PCM malfunction
SYSTEM WIRING DIAGRAM  -
CAUTION:
  • Verify the malfunction symptom according to not only the PID value but also the symptom troubleshooting.
RELATED PIDS

Monitor item (Definition) Unit/Condition Condition/Specification (Reference)
APP1 %
  • Accelerator pedal released: approx. 16 % 
  • Accelerator pedal depressed: approx. 80 % 
V
  • Accelerator pedal released: approx. 0.8 V 
  • Accelerator pedal depressed: approx. 4 V 
APP2 %
  • Accelerator pedal released: approx. 8 % 
  • Accelerator pedal depressed: approx. 40 % 
V
  • Accelerator pedal released: approx. 0.4 V 
  • Accelerator pedal depressed: approx. 2 V 
ECT °C, °F
  • Displays the ECT
V
  • ECT is 20°C {68°F}: approx. 3.10 V 
  • ECT is 40°C {104°F}: approx. 2.16 V 
  • ECT is 60°C {140°F}: approx. 1.40 V 
  • ECT is 80°C {176°F}: approx. 0.87 V 
  • ECT is 100°C {212°F}: approx. 0.54 V 
IAT °C, °F
  • Displays the IAT (No. 1)
V
  • IAT is 20°C {68°F}: approx. 2.64 V 
  • IAT is 40°C {104°F}: approx. 1.80 V 
  • IAT is 60°C {140°F}: approx. 1.14 V 
MAF g/sec
  • Displays the MAF
V
  • Switch the ignition to ON (MAF: 0.59 g/s {0.078 lb/min}): approx. 0.72 V 
  • Idle (after warm up) (MAF: 2.17 g/s {0.287 lb/min}): approx. 0.86 V 
  • Racing (engine speed is 2,000 rpm)  (MAF: 4.73 g/s {0.626 lb/min}): approx. 1.07 V 
RPM RPM
  • Displays the engine speed
TP REL %
  • Accelerator pedal released: approx. 12 % 
  • Accelerator pedal depressed: approx. 82 % 
VSS KPH, MPH
  • Displays the vehicle speed
VT_IN_ACT °
  • Displays the actual intake valve timing
VT_IN_DES °
  • Displays the desired intake valve timing
FUEL_PRES KPa {MPa}, mBar {Bar}, psi, in H20
  • Displays the fuel pressure
V
  • Fuel pressure is 3.0 MPa {31 kgf/cm 2  , 435 psi}: approx. 0.92 V 
  • Fuel pressure is 4.8 MPa {49 kgf/cm 2  , 696 psi}: approx. 1.17 V 
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