Fault code P0271 – a step-by-step guide to diagnosing and fixing it

Error code P0271 is displayed and the check engine light is on - what does this mean?

The DTC P0271 is recognized by the OBD/EOBD system if there is a problem with the injection valve circuit of cylinder 4. This fault code indicates a fault in the fuel injection system, which can lead to uneven engine running. The exact designation may vary for different manufacturers, but always refers to problems with the fourth cylinder injection valve.

What causes can this error code have?

• Defective injection valve on cylinder 4
• Damaged cable connection to the injection valve
• Corroded or loose plug connections
• Defective engine control unit (ECU)
• Short circuit in the injection valve circuit
• Interrupted ground connection
• Dirty or clogged injection valve
• Defective fuel pump or low fuel pressure

What symptoms occur in parallel with fault code P0271?

• Engine performance: Noticeable loss of power and jerky engine running
• Fuel consumption: Increased consumption due to inefficient combustion
• Starting behavior: Difficult cold starts or rough idling
• Exhaust emissions: Increased pollutant levels and black smoke
• Engine noise: Uneven running noise or knocking
• Misfiring: Misfiring in the fourth cylinder

How can the problem with error code P0271 be resolved?

• The elimination of trouble code P0271 requires a systematic diagnosis of the injection system.
• Replace the injection valve of cylinder 4 completely and check the electrical connections
• Check the wiring harness to the injection valve for damage and replace defective lines
• Clean plug connections, check for corrosion and replace if necessary
• Measure fuel pressure and replace fuel pump or filter if values are low
• Diagnose engine control unit and replace or reprogram if defective
• Have the injection valve professionally cleaned or carry out ultrasonic cleaning
• Check the ground points of the injection system and repair corroded connections