Fault code P0302 – a step-by-step guide to diagnosing and fixing it

This code indicates that one or multiple misfires have been detected in the second engine cylinder. The control unit continuously monitors the rotation speed of the crankshaft. When the speed changes by 2% or more within a certain timeframe, the unit stores this code. This fault is often caused by low fuel or compression levels, engine camshaft or crankshaft problems, and spark plug malfunctions.

• A worn or faulty engine spark plugs. The plugs can fail due to a rich air-fuel mixture, a bad car fuel filter or leaky head gasket, causing fouling and contamination.
• Distributor malfunctions due to a worn rotor
• Damage to the high-voltage wires or coils
• A stretched timing chain or belt, a worn out camshaft, or mismatching timing marks
• A defective crankshaft, camshaft, MAF or oxygen sensor
• Low fuel pressure or a broken fuel pump. Fuel contamination and electrical faults are the most common causes of pump failure.
• Clogged or malfunctioning fuel injectors
• Low compression due to worn cylinder and piston components or bad valves
• A damaged crankcase ventilation hose or defective EGR valve
• A leaking head gasket or vacuum leaks

• Increased fuel consumption
• A loss of engine power
• Stalling when idling
• Jerking or hesitation when accelerating
• A strong fuel smell coming from the exhaust
• Starting difficulties
• An increase in engine vibrations

• Scan for DTCs using an OBD2 tool to quickly identify the cause. Once you have read through the data, reset the codes and take the vehicle for a test drive to see whether the check engine comes on again
• Make sure there are no loose connectors or ground wires which could be causing the misfires. Check the high-voltage wires, spark plugs, and coils for damage. If the car features coil packs, check the pack in cylinder 2 for signs of arcing. Check whether the distributor cap is sealed properly and examine the condition of the rotor. Replace the parts if necessary.
• Clogged injectors need to be cleaned or “flushed” to clear blockages in the system. Cleaning additives can be purchased for this purpose. You can test for low fuel pressure using a pressure gauge or by scanning the system with an OBD2 scanner. For example, DTC P0203 indicates that the electric fuel pump (diesel or petrol) isn’t working properly.
• Clean the valves using a special cleaning spray.
• Any leaks will need to be addressed promptly. You may need to replace the seals, pipes or cylinder head gasket. Make sure that the clamps are fastened properly.
• Replace any worn valve train parts, including a stretched timing belt or chain and worn out gears. Adjust the timing belt/chain tension if necessary.
• Test the voltage output of the associated sensors using a multimeter.
• If the exhaust fumes smell like sulphur or rotten egg, check the catalytic converter.