Error Codes

Error codes for catalytic converter, EGR, OPF, GPF, DPF, oxygen sensor and turbocharger

Emission-related error codes are among the most common reasons for an illuminated check engine light. They may concern the catalytic converter, the exhaust gas recirculation system (EGR), the gasoline particulate filter (OPF/GPF), the diesel particulate filter (DPF), the oxygen sensor or the turbocharger boost-pressure control.

On this blog overview page, you will find explanations of important OBD error codes, their possible causes and typical effects. You will also learn why certain faults can reappear after a repair, component replacement or modification of the exhaust system.

Which emission-related error codes occur particularly often?

Catalytic converter error codes

Error codes in the range from P0420 to P0434 often indicate that the catalytic converter efficiency calculated by the engine control unit is below the expected threshold. The best-known messages include:

• P0420: Catalyst system efficiency below threshold, bank 1
• P0421: Warm-up catalyst efficiency below threshold, bank 1
• P0430: Catalyst system efficiency below threshold, bank 2
• P0431: Warm-up catalyst efficiency below threshold, bank 2

Possible causes include an aged or damaged catalytic converter, deviations in the oxygen-sensor signals, leaks in the exhaust system or changed readings after installing a downpipe or a different exhaust system.

EGR error codes

Exhaust gas recirculation is internationally abbreviated as EGR. Typical error codes are found in the range from P0400 to P0409.

• P0400: Exhaust gas recirculation system malfunction
• P0401: Exhaust gas recirculation flow insufficient
• P0402: Exhaust gas recirculation flow excessive
• P0403: Exhaust gas recirculation control circuit malfunction
• P0404: Exhaust gas recirculation range or performance fault

Deposits, a sticking EGR valve, incorrect sensor readings, leaking lines or electrical faults can cause the check engine light to switch on repeatedly.

OPF, GPF and DPF error codes

Particulate filters monitor, among other things, loading, differential pressure, temperature and regeneration processes. Faults may occur if a filter is blocked, regeneration is not completed or sensor readings are outside the expected ranges.

• P2002: Particulate filter efficiency below threshold
• P2003: Particulate filter efficiency below threshold, bank 2
• P242F: Particulate filter restricted by ash accumulation
• P2452 to P2455: Faults in the differential-pressure sensor area
• P2463: Particulate filter restricted by soot accumulation

Vehicles with a modified OPF, GPF or DPF, a downpipe or an adapted exhaust system may also develop recurring efficiency and plausibility faults.

Oxygen-sensor error codes

Oxygen sensors measure the oxygen content in the exhaust gas and provide important readings for mixture control and catalytic converter monitoring. Common messages include:

• P0130: Oxygen sensor circuit malfunction, bank 1 sensor 1
• P0131: Oxygen sensor signal voltage too low
• P0132: Oxygen sensor signal voltage too high
• P0133: Oxygen sensor response too slow
• P0136: Oxygen sensor circuit malfunction, bank 1 sensor 2

In addition to a defective sensor, damaged cables, exhaust leaks, combustion problems or a changed exhaust-gas flow may also be responsible.

Turbocharger and boost-pressure error codes

Boost-pressure control faults may be caused by leaks, sticking adjustment mechanisms, defective pressure sensors, wastegate problems or deviations between target and actual boost pressure.

• P0234: Boost-pressure control limit exceeded
• P0299: Boost pressure too low
• P0243: Boost-pressure control valve circuit malfunction
• P2263: Turbocharger or boost system performance fault

Why do error codes return after being cleared?

Manually clearing an error code does not automatically eliminate its cause. If the engine control unit detects the same deviation again, the fault is stored again and the check engine light may illuminate once more.

Typical reasons for recurring fault messages include:

• Ageing or reduced efficiency of the catalytic converter and particulate filter
• Intermittent or borderline readings from sensors and oxygen sensors
• Deposits or mechanical problems in the EGR system
• Deviations caused by downpipes or modified exhaust systems
• Engine-control-unit learning and adaptation processes that have not been fully completed
• Faults that occur only under certain load, temperature or driving conditions

How does OBD-Killer work?

OBD-Killer is connected externally to the vehicle's OBD diagnostic socket. During the initial installation, it learns the error codes that are active at that time. These are then treated as expected faults.

If a learned fault occurs again, OBD-Killer attempts to clear it automatically from the fault memory. This can prevent the check engine light from remaining permanently illuminated because of the same expected fault. Error codes that have not been learned remain visible.

OBD-Killer does not modify the original software or the programming of the engine control unit. The vehicle must support clearing the relevant error code while the engine is running, and the required on-board voltage must reach at least 13.3 V.

Which vehicles is OBD-Killer suitable for?

OBD-Killer is intended for almost all compatible vehicles from model year 2008 onwards that use compatible OBD communication. Use with older vehicles may also be possible if the required connections are present in the OBD diagnostic socket.

When the device is moved to another vehicle, OBD-Killer recognises the new vehicle identification number and resets its learned values. It can then be taught again on the new vehicle.

Look up error codes in the blog

The individual blog articles explain the respective error codes in greater detail. There you will find information about the meaning of the code, possible causes, typical symptoms and suitable inspection steps.

The content is intended as technical guidance. Before using OBD-Killer, you should check whether a safety-related or serious technical defect is present.

Frequently asked questions