P0400 when ambient temperature is above 12 degrees.

[jtg]

I have had the P0400 error for about a year now and it comes on when at idle sitting at lights or a junction. The warning light goes out when up at speed at revs are over 2500. If the temperature drops below 12 degrees the fault doesn't occur.

Any ideas as to the cause?

Thanks

[bobssignum]

Hi jtg
Obviously you know that the p0400 code relates to the EGR , i am just wondering if you have any other fault codes as well , the reason i am asking is it may be that another sensor is faulty and ,its sending false data to the ecu possible sensor ,s that could give false readings would be ambient air sensor , barometric pressure sensor , boost sensor or possible the tps if you have it on your DTi

[jtg]

Thanks for the fast reply. I have replaced all egr related items and tested the function with open-com and all ok except for P0400 and 2 codes related to cruise control. I will have to test the temperature sensors some how.

[Sabreman]

Hi folks. If you can find my recent posts you will see that I have been plagued with the same fault code for months. The local VX dealer told me that the EGR valve needed replacing at a cost of £300. They were also trying to take me or to be precise my warranty company) for £900 for suction control valves in the high pressure pump when there were not the slightest symptoms of any fault there - and still aren't a few thousand miles down the road.

Subsequently EGR replaced by a local trusted mechanic and lo-and-behold, EGR valve as clean as one could expect in that environment. Next up - 0400 fault showing again with same lumpy running symptoms at low revs and speeds (same as yours). Local mechanic is not getting any underlying data on his diagnostic wizzardry but suspects something down line - like an air flow meter etc. Watch this space. '07 model Siggy V6 3.0 SCTi

[jtg]

Subsequently EGR replaced by a local trusted mechanic and lo-and-behold, EGR valve as clean as one could expect in that environment. Next up - 0400 fault showing again with same lumpy running symptoms at low revs and speeds (same as yours). Local mechanic is not getting any underlying data on his diagnostic wizzardry but suspects something down line - like an air flow meter etc. Watch this space. '07 model Siggy V6 3.0 SCTi

Any more updates on your P0400 error?

[Sabreman]

Since my last post the car has behaved itself - until today !! Slow running in low gears (auto) in hilly/bendy lanes in the Dales when spanner light came on and car lost power and went into limp-home mode. Have been carrying diagnostic thingy in car and pulled into side with engine still running and plugged in. Showed fault code P0400 and text indicated EGR fault, but there was no 'freeze frame' stored - presumably to identify more about what the problem was. Stopped engine and fault disappeared immediately. I re-checked diagnosis which remained the same.

Remember that this is a brand new EGR and the old one still looked like new when we got it on the bench. Going to see my diagnostic man tomorrow as it looks like some gizmo further down the pipework is misbehaving.

The symptoms in no way mirror those described both by the Vx agent, and others on this site, as being an SCV problem - indeed the fault code for that has never shown.