P0302

What P0302 Means

Code P0302 indicates that misfires have been detected in cylinder 2. The engine control unit (DME) sets this code when it registers a disruption in the combustion process in cylinder No. 2. Misfires can be caused by a weak spark, fuel delivery problems, or mechanical faults.

The most common causes, as with code P0301 (cylinder 1 misfire), include a faulty ignition coil, spark plug, or fuel injector. On N55 engines, ignition coil failure is especially common due to thermal cycling (heat-cool cycles), which accelerates wear on the coil's insulation and internal components.

Symptoms

• Check Engine light: comes on or flashes on the instrument cluster.
• Rough idle: the engine runs unevenly, with possible vibration.
• Power loss: reduced pull during acceleration and under load.
• Vibration: felt in the body or through the steering wheel, especially at idle.
• Possible limp mode: rpm and power are limited to protect the engine and catalytic converter.

Diagnosis and Repair

1. Check the Ignition Coil

• Swap the ignition coil from cylinder 2 with another cylinder (cylinder 1, for example).
• If the misfire code moves to the other cylinder after the swap (for example, P0301 appears), the coil is faulty. Replace it with an original: 12138616153.

2. Inspect the Spark Plug

• Remove the cylinder 2 spark plug and inspect it for wear, deposits, or damage.
• Replace it with an original if needed: 12120037563.

3. Check the Fuel Injector

• Check the cylinder 2 injector: winding resistance, spray pattern, and freedom from clogging.
• Replace the injector if it's faulty.

4. Compression Test

• If replacing the coil and plug doesn't fix the problem, run a compression test on cylinder 2 to rule out mechanical faults (worn piston rings, valves, and so on).

Secondary Damage

Ignoring code P0302 and continuing to drive with misfires can lead to the following (same as with code P0301):

• Catalytic converter damage: unburned fuel reaches the exhaust system and causes overheating and converter breakdown.
• Oxygen sensor damage: unburned fuel and incomplete-combustion byproducts contaminate the sensor's sensing element.
• Cylinder wall wear: prolonged misfires can dilute the oil with fuel and increase wear on the cylinder bore.

Do the repair as soon as possible to avoid costly consequences.