Fault code P0428 – a step-by-step guide to diagnosing and fixing it

Error code P0428 is displayed and the check engine light is on - what does this mean?

The OBD system detects a fault in the catalytic converter temperature sensor of cylinder 1 if the measured temperature is too high. This DTC P0428 indicates that the catalytic converter is overheating or the temperature sensor is defective. This error code can be interpreted slightly differently for different manufacturers, but it always relates to the exhaust gas purification system.

What causes can this error code have?

• Defective catalytic converter temperature sensor
• Overheated catalytic converter due to excessively rich fuel/air mixture
• Damaged wiring to the temperature sensor
• Corroded or loose plug connections
• Defective engine control unit (ECU)
• Clogged air filter or fuel filter
• Defective lambda sensors
• Faulty fuel injection

What symptoms occur in parallel with fault code P0428?

• Check engine light: Permanent display of the warning light in the dashboard
• Loss of power: Noticeable reduction in engine power, especially when accelerating
• Increased fuel consumption: Significantly higher consumption than usual
• Uneven engine running: Engine runs unevenly or jerks when idling
• Exhaust odor: Unusual or intense smell from the exhaust
• Starting problems: Delayed starting or difficulty starting the engine

How can the problem with error code P0428 be rectified?

• The repair requires a systematic approach, as several components may be affected.
• Replacement of the defective catalytic converter temperature sensor with an original part or equivalent quality, including checking for correct positioning and sealing
• Complete inspection and repair of the wiring from the sensor to the engine control unit, including insulation of damaged areas and cleaning of corroded contacts
• Replacement of the overheated catalytic converter and simultaneous elimination of the cause of the overheating by adjusting the fuel-air mixture
• Cleaning or replacing clogged filters (air and fuel filters) and checking the entire intake and fuel system
• Diagnosis and repair of defective lambda sensors, which can lead to an unbalanced fuel-air ratio
• Checking and, if necessary, reprogramming or replacing the engine control unit in the event of electronic defects