DTC P0300: Random Misfire Detected: General Description
The crankshaft vibrates slightly when each cylinder fires. If a misfire occurs, the crankshaft rotation speed changes rapidly. The engine control module (ECM) monitors the crankshaft rotation speed based on the output pulses from the crankshaft position (CKP) sensor. By monitoring changes in the crankshaft rotation speed, the ECM counts the number of misfires and determines which cylinder is misfiring. If more than one DTC from P0301 through P0304 has been stored while misfires in multiple cylinders are detected, a malfunction is detected and a DTC is stored.
There are two types of misfire detection.
Type 1 (1 drive cycle): When the number of misfires per 200 engine revolutions reaches the level that damages the three way catalyst (TWC), a DTC is stored and the MIL blinks. When the misfire ceases, the MIL remains on steady instead of blinking.
Type 2 (2 drive cycles): When the number of misfires per 1,000 engine revolutions reaches the level that affects FTP mode exhaust emissions, a DTC is stored and the MIL comes on.
MONITOR EXECUTION, SEQUENCE, DURATION, DTC TYPE, OBD STATUS
| Execution |
Continuous |
| Sequence |
None |
| Duration |
Type 1 |
Every 200 rpm |
| Type 2 |
Every 1,000 rpm |
| DTC Type |
Two drive cycles, MIL ON |
| OBD Status |
PASSED/FAILED/EXECUTING/OUT OF (TEST) CONDITION |
ENABLE CONDITIONS CHART
| Condition |
Minimum |
Maximum |
| Engine coolant temperature |
14°F (-10°C) |
- |
| 68°F (20°C) |
| Engine speed |
500 rpm |
8,000 rpm |
| MAP value |
900 rpm |
22 kPa (6.4 in.Hg, 162 mmHg) |
- |
| 2,000 rpm |
22 kPa (6.4 in.Hg, 161 mmHg) |
| Fuel feedback |
Other than during fuel cut-off operation |
| No active DTCs |
P0107, P0108, P0117, P0118, P0122, P0123, P0222, P0223, P0335, P0339, P1109, P1128, P1129, P2227, P2228, P2229 |
| Other |
Test-drive on a flat road to avoid misdetection |