Error code P0423 is displayed and the check engine light is on - what does this mean?
The OBD/EOBD system has detected insufficient efficiency of the heated catalytic converter in bank 1. This DTC P0423 fault code indicates that the catalytic converter is no longer working properly and exhaust gas purification is impaired. For various manufacturers, this trouble code can also be referred to as "Heated Catalyst Efficiency Below Threshold Bank 1".
What can cause this error code?
- Defective or used catalytic converter
- Faulty lambda sensors before or after the catalytic converter
- Damaged cable connections to the oxygen sensors
- Engine problems such as incomplete combustion
- Defective ignition coils or spark plugs
- Fuel pump problems or dirty injection nozzles
- Air leaks in the intake system
- Defective engine control unit (ECU)
What symptoms occur in parallel with fault code P0423?
- Loss of power: The vehicle shows reduced engine power and poor acceleration
- Increased fuel consumption: The engine requires more fuel than usual
- Uneven idling: The engine runs unevenly at idle speed
- Exhaust odor: Unusual smells from the exhaust, especially of rotten eggs
- Starting problems: Difficult cold starting characteristics of the engine
- Jerking: Uneven engine running while driving
How to fix the problem of error code P0423?
- Repairing this EOBD fault code requires a systematic diagnosis of the exhaust system.
- Replacing the defective catalytic converter with a new or refurbished part, including professional installation and gasket replacement
- Replacing the lambda sensors upstream and downstream of the catalytic converter if they are out of specification or damaged
- Repairing or replacing damaged cable connections and connectors to the oxygen sensors with appropriate OEM parts
- Correction of engine problems by replacing defective ignition coils, spark plugs or injectors that lead to incomplete combustion
- Cleaning or replacing the air filter and repairing air leaks in the intake system to restore the correct air-fuel mixture
- Professional engine diagnostics and, if necessary, repair of the engine control unit by a specialist workshop
FAQ - Frequently asked questions about DTC P0423
Can I continue driving with error code P0423?
It is possible to drive for a short time, but you should visit a workshop as soon as possible. The defective catalytic converter can lead to increased emissions and further engine damage. In addition, you will not pass the next emissions test.
How much does it cost to repair error code P0423?
The costs vary depending on the cause: Lambda sensors cost 80-200 euros, a new catalytic converter between 300-1200 euros. Minor repairs such as cable repairs are between 50-150 euros. The working time is usually 2-4 hours.
How long does a catalytic converter normally last?
A catalytic converter typically has a service life of 150,000-200,000 kilometers. Poor maintenance or engine problems can cause it to fail earlier. Regular maintenance extends the service life considerably.
Can I repair error code P0423 myself?
Simple work such as replacing spark plugs is possible, but catalytic converter diagnosis requires professional equipment. Lambda probes and catalytic converter replacement should be carried out by a specialist workshop.
Does P0423 automatically lead to an MOT refusal?
Yes, this OBD code leads to a refusal of the main inspection. The vehicle must be repaired and the fault memory deleted before a successful emissions test is possible.
How can I avoid P0423 in the future?
Regular maintenance is crucial: use high-quality fuel, change the air filter and spark plugs in good time and have engine problems repaired immediately. Avoid short journeys as the catalytic converter needs operating temperature.
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