OBD2 CODE

P0400 Exhaust gas recirculation (EGR) flow fault

Urgency medium

A code identifies a signal or system that needs to be checked, not a part you should replace.

Exhaust Gas Recirculation Flow

The EGR valve sends part of the exhaust gas back to the intake to lower the combustion temperature and the nitrogen oxides (NOx).

What the car has detected

The amount of gas going back to the intake is not what the ECU expects: too little or too much.

The car usually keeps running, though it may lack power, smoke or stall at idle. Emissions rise and it may fail the inspection. Have it checked soon.

Ask for the EGR valve, its pipes and its wiring to be checked.

Go to a garage in the next few days. Lots of short trips clog the EGR: a long road trip now and then helps.

A generic X-ray car with this code's area marked in red: engine. It is a guide, not the layout of your model.

Injectors, dual-mass flywheel, turbo and EGR on the first 2.0 D-4D (1CD-FTV)Injection / turbo

Engine / equipment: First-generation 2.0 D-4D (1CD-FTV): Avensis, Avensis Verso, Corolla, Corolla Verso, RAV4 and Previa
Period mentioned: Approx. 1999–2006
Symptoms: Hard starting, hesitation and loss of power, black smoke; EGR (P0400) or turbo-control codes; flywheel noise.
Possible cause described: Denso injectors that fail often and can hardly be repaired, pump suction control valves (SCV), leaking injector seals and soot in the EGR; also the dual-mass flywheel and turbo. On the second generation (1AD, from 2006) the typical fault is different: head gasket and oil consumption.
Check for the garage: Read the codes, check the fuel filter and for air ingress, test the injectors and SCV valves and clean the EGR before replacing expensive parts.
Cost cited in the source: No verified estimate; ask the garage for a quote.A rough figure from the original database, not an up-to-date quote.

EGR valve sticking with deposits on the 1.5 dCiExhaust and emissions

Engine / equipment: 1.5 dCi (K9K) with an electric EGR valve
Period mentioned: No specific period published
Symptoms: Uneven idle, jerks when accelerating, lack of power or the engine going into limp mode, sometimes with the engine warning light on.
Possible cause described: Soot and oil deposits leave the EGR valve stiff, stuck closed or not closing fully. According to Pierburg it is rarely a fault of the valve itself: the oil comes through the crankcase breather, a turbo with worn bearings or a blocked oil return, late oil changes or too high a level, and many short trips, above all in winter.
Check for the garage: At the workshop: read the codes with diagnostic equipment (EOBD P0400 to P0404 or P0172; Renault DF077, DF084 or DF241), test the valve electrically and its opening with the engine warm, and find where the oil comes from (breather, turbo, level). Pierburg advises against cleaning it, as it can be damaged: it is replaced if faulty, and an engine ECU update sometimes solves it.
Cost cited in the source: No verified estimate; ask the workshop for a quote for the EGR valve.A rough figure from the original database, not an up-to-date quote.

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