Fault code P0427 – a step-by-step guide to diagnosing and fixing it

Error code P0427 is displayed and the check engine light is on - what does this mean?

The DTC P0427 indicates that the OBD system has detected too low a voltage on the catalytic converter heating system of bank 1. This fault code relates to the electrical supply to the catalytic converter heating element, which ensures the optimum operating temperature of the catalytic converter. This code may have slightly different names for different manufacturers, but always refers to the catalytic converter heating system.

What causes can this error code have?

• Defective catalytic converter heating element
• Damaged wiring to the heating system
• Corroded or loose plug connections
• Defective control unit for the catalytic converter heating system
• Blown fuse in the heating circuit
• Short circuit in the electrical wiring
• Defective lambda sensor
• Problems with the engine control unit (ECU)

What symptoms occur in parallel with fault code P0427?

• Engine indicator light: Lights up continuously on the dashboard
• Increased emissions: Poorer exhaust gas values at the main inspection
• Extended warm-up phase: Engine takes longer to reach operating temperature
• Loss of power: Reduced engine power when the engine is cold
• Increased fuel consumption: Especially during the warm-up phase
• Jerking at idling speed: Engine runs unevenly at low temperatures

How can the problem of error code P0427 be rectified?

• The repair requires a systematic diagnosis of the electrical components of the catalytic converter heating system.
• Checking and replacing the fuse in the catalytic converter heating circuit and checking the entire electrical supply
• Measurement of the voltage and resistance on the catalytic converter heating element and, if defective, complete replacement of the catalytic converter
• Inspection of all cable connections to the heating system, repair of damaged cables and cleaning of corroded contacts
• Replacing defective plug connections and checking the contact quality in the entire heating circuit
• Diagnosis and, if necessary, replacement of the lambda sensors and calibration of the system
• Checking the engine control unit and updating the software or replacing it in the event of hardware defects