Exhaust gas recirculation (EGR)
Exhaust gas recirculation: the EGR valve, its actuator and position sensor. Part of the exhaust is returned to the intake to lower the combustion temperature — and soot returns with it, which is what coats the valve.
7 codes in this section, 7 with a guide
What it usually turns out to be
- The valve is almost always coked up rather than dead: taking it off to look costs ten minutes.
- Insufficient flow more often means a blocked passage than a broken valve.
- After cleaning the code may come back once — the unit does not test the flow on every trip.
P0400Exhaust gas recirculation (EGR) — malfunctionguideP0401EGR flow insufficient detectedguideP0402EGR flow excessive detectedguideP0403EGR valve — control circuit malfunctionguideP0404EGR valve — position out of range, stickingguideP0405EGR position sensor — low signalguideP0409EGR position sensor — circuit malfunctionguide
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Other sections
Fuel and air metering, general 33Intake measuring sensors 17Oxygen sensors 19Throttle and accelerator pedal 15Mixture: lean and rich 11Fuel and air metering: injectors 25Ignition system and misfires 29Secondary air injection 3Catalytic converter 4Canister and purge valves 9Fuel vapour leaks 7Fuel level in the tank 4Diesel particulate filter 6Idle and auxiliary systems 22Control module and its circuits 21Transmission 17Communication between modules 20Brakes, ABS and stability control 17Body, airbags and lighting 12