ECU V6 still playing up but some new diagnostics

Paulxmski · Post by **Paulxmski** » 19 Nov 2004, 04:32

Hi,
Yes I still haven't been able to track down the ECU problem on my V6. At the moment I'm still removing the ECU connector and replacing it when the poor start condition (chugging and no acceleration) occurs. Tonight when it happened (well it would as it was snowing) I noticed that the fan for the airconditioning which is always set at auto did not come on even after I drove it up the road some way in that condition. When I stopped in a layby and reset the ECU i.e pulled and replaced the plug. When I restarted the cabin fan came on full blast. Any ideas on how the aircon might be affected by the state of the ECU Please [?][?][?][?][:(]

xantiav6 · Post by **xantiav6** » 19 Nov 2004, 11:59

I done't know any details of the software on your model car, but it sounds like the Engine Management has gone into "limp home" mode and this disables the A/C to reduce unnecessary load on the engine. If there is a limp home mode, it could be triggered by the failure of just about any sensor, or a bad connection in the wiring. Good luck.

Paulxmski · Post by **Paulxmski** » 21 Nov 2004, 08:00

Hi Mike thanks for that info. I don't think it is limp home since when it is in this condition, which only occurs on initial cold start, it just won't go at all especially on even a slight incline when the speed drops to 5mph and it stalls and switches the injectors off until the revs drop below about 1500. I think it might be something to do with the accelerator overrun. Anyway. I just pull the plug now and after that it goes fine. I would like to fix it but it's not worth spending the money on computer diagnostics as it was a cheap to buy car anyway

David Goddard · Post by **David Goddard** » 25 Nov 2004, 04:35

Sounds like the coolant temperature transmitter. On failure these RTD's can drop to zero ohms - the ECU then thinks the engine is hot, when in facts it's cold and needs a richer mixture. On Xantia's this transmitter is green.

Paulxmski · Post by **Paulxmski** » 27 Nov 2004, 04:28

Thanks David, I will investigate that.

DomF9 · Post by **DomF9** » 27 Nov 2004, 05:57

Hi All
My SI 2L Turbo Auto seems to have this "limp home" problem - cuts out at 4500rpm and the engine management light on. How do you reset it, and how long does it last for? Oddly, all week it's been cutting out but tonight on several occasions it has quite happily accelerated to 6000rpm without cutting out, but still with the management light on. Any clues, people?

Paulxmski · Post by **Paulxmski** » 01 Dec 2004, 04:07

Hi DomF9,
I don't think you have a similar problem to mine since I can't get beyond 1500rpm on a cold start before the engine cuts out then cuts back in at 1000 rpm. Also my engine management light has never come on otherwise I would really be freaked out. However have you tried stopping the car when it cuts back to 4500rpm and pulling the plug off the ECU and replacing it. In order to make it simple to do this I took the front plastic fuse box off (discovering that the relays were just lying in the bottom of the box since all their tabs were broken off) and put it in the boot. Then it's just a matter of flippig the lid off the ECU box, pressing in the metal tag with one finger and pulling up the plug from the right side since it is hooked under a plastic lug on the left side. If you're not very careful you will either bust your nail, skin the finger or both as the plug unhooks.

I don't know what effect this may have in your case but in my case it relieves the problem for a day or two at most.[xx(]