Advanced Diagnostics

Advanced Diagnostics - DTC P0301: No. 1 Cylinder Misfire Detected
Advanced Diagnostics - DTC P0302: No. 2 Cylinder Misfire Detected
Advanced Diagnostics - DTC P0303: No. 3 Cylinder Misfire Detected
Advanced Diagnostics - DTC P0304: No. 4 Cylinder Misfire Detected
Advanced Diagnostics - DTC P0305: No. 5 Cylinder Misfire Detected
Advanced Diagnostics - DTC P0306: No. 6 Cylinder Misfire Detected






General Description
The crankshaft vibrates slightly when each cylinder fires. If a misfire occurs, the crankshaft rotation speed changes rapidly. The powertrain control module (PCM) monitors engine misfiring based on the output pulses from the crankshaft position (CKP) sensor, counts the number of misfires, and determines which cylinder is misfiring. If a misfire is detected, a DTC is stored.

There are two types of misfire detection:
Type 1: When the number of misfires per 200 engine revolutions reaches the level that can damage the three way catalyst (TWC), a DTC is stored and the MIL blinks. When the misfire ceases, the MIL stays on instead of blinking.
Type 2: 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






Enable Conditions






Malfunction Threshold






Driving Pattern






1. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on.
2. Drive the vehicle at a speed between 15 - 75 mph (24 - 120 km/h) for at least 3 minutes.
3. Stop the vehicle, and let the engine idle for at least 3 minutes.

- When freeze data is stored, drive the vehicle under those conditions instead of Driving Patterns 2 or 3.
- When you have difficulty duplicating the DTC because of road conditions and traffic situations, repeat the driving pattern several times.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC

Misfire Type 1:
- If a type 1 misfire (catalyst damaging) occurs once, the MIL blinks once per second, a Pending DTC is stored, and the high rpm fuel injection stop system activates. The fuel injection stops, at high rpm only, on the cylinder that has the highest misfire counts. The MIL then continues to blink and the fuel injection stays off at high rpm, until the drive is completed.
- If a type 1 misfire occurs during a second drive cycle, the MIL and fuel injection behave the same and a Confirmed DTC is stored.
- After a type 1 misfire has been detected during two drive cycles, the MIL comes on and stays on beginning with the third drive cycle, unless the Pending DTC has been cleared by the PCM***. Even if the MIL is on, it will start blinking if a type 1 misfire occurs.
- If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Misfire Type 2:
If a type 2 misfire (emission-related but not severe enough to immediately damage the catalyst) occurs, a Pending DTC is stored, but the MIL does not come on or blink. If a type 2 misfire occurs during a second drive cycle, the MIL comes on and stays on unless the Pending DTC has been cleared by the PCM***.

*** The Pending DTC is erased if either of these conditions is met:
- The vehicle is operated at least once under the same driving conditions as the first misfire detection, and no misfire is detected.
- 80 drive cycles, regardless of driving conditions, are completed with no misfire detected.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive drive cycles in which the engine conditions are similar to the first time the malfunction was detected. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.