EGR reduces the temperature of combustion in engines to control nitrogen oxide emissions. Nitrogen oxides are produced when the combustion chamber temperature is too high. EGR helps reduce NOx gas emissions. EGR systems can malfunction just like any other system or component in the engine. P0402 is one of the OBD II codes that relate to EGR. There are many different EGR systems in use today. Despite the differences in features, all EGR systems use a type of EGR Valve. The PCM opens the EGR valve when conditions are ideal, allowing exhaust gas to be recirculated back into the intake manifold of the engine. By feeding these waste gases into the engine, combustion temperatures are lowered and NOx emissions are reduced.
EGR can only be used in certain conditions. The PCM will activate the engine fault code P0402 if it detects excessive EGR.
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What are the possible causes of fault code P0402?
- A faulty differential pressure sensor is found on some vehicles (DPFE sensor).
- Faulty EGR Temperature Sensor
- Blockage of the EGR channels due to carbon buildup
- EGR valve faulty
- Vacuum insufficient to open EGR valve
- Damaged cables and loose connections
- EGR Control Circuit Problems
- PCM Problems
What are the symptoms of fault code P0402?
In general, this code is associated with driving problems. Symptoms may vary depending upon your vehicle. The P0402 code can cause the following symptoms:
- The engine fault light is illuminated
- Engine speed fluctuation at idle
- The engine is stalling
- The vehicle may not start in extreme cases
How to Fix Error Code P0402?
- Replace a defective EGR valve after inspecting, and repairing if needed, vacuum hoses and cables
- Replace a catalytic convertor that has broken in the exhaust
- Replace the EGR Temperature Sensor
- Cleaning carbon deposits off the EGR temperature Sensor
- Replace the EGR backpressure control valve
How serious is the P0402 fault code?
An EGR with excessive flow may cause the engine to hesitate or stall during acceleration, or to run poorly at idle. If the catalytic converter becomes blocked due to this code, it may cause the engine to lose power and fail to run.
