P0303 P0303 OBD-II: Misfire in Cylinder 3 Detected

P0303 Severity Moderate

What P0303 means for you

This code indicates a misfire in cylinder three, which can lead to performance issues but is not immediately critical.

Symptoms

Flashing Check Engine Light
Engine running roughly
Hesitation or jerking during acceleration
In many instances, the driver may not experience significant issues
However, some drivers might notice performance drops, such as stalling at traffic stops or rough idling
Possible misfires or reduced power, particularly noticeable during acceleration
Decreased fuel efficiency

Common causes

This code is triggered when the engine control module (PCM) identifies that cylinder three is not adequately contributing to the engine's operation.

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What this code means

The P0303 code signifies that the engine control module has detected a misfire in cylinder three, which disrupts the engine's performance. This occurs when the PCM observes a significant deviation in RPM between the firing of the cylinders, particularly if cylinder three is not firing effectively.

How a workshop diagnoses it

1. Use a scan tool to retrieve the P0303 code and any related codes. 2. Record freeze frame data to understand the conditions under which the code was set. 3. Perform a test drive to replicate the conditions, monitoring engine load, throttle position, RPM, and vehicle speed. 4. If available, check the misfire counter for specific cylinders. 5. If no misfire counter is present, consider swapping components like coils or spark plugs to identify the faulty part.