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Replacing the engine ECU |
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ChrisW
 
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  Member No: #1335
Location: Surrey |
Has anyone replaced the engine ECU or can advise me on this? It's a 2008 2.7HDI Lignage. The ECU sometimes puts the car in limp mode for no apparent reason. No fault code on my Ancel code reader. Normally when the car goes into limp mode for whatever reason, simply turning it off, waiting a few seconds, and restarting gets it out of limp mode. But sometimes, when it is restarted, it goes straight back into limp mode even without touching the accelerator, putting it into drive or any other controls. This happened yesterday and I had to do a 100 mile journey in limp mode. It was then parked for a few hours. The fault corrected itself and the journey home was perfect. I don't know if this is a "real" fault with the engine or a fault with the ECU. I can buy a "tested and guaranteed" engine ecu from ebay taken from a C6 with the identical engine. So this could be a quick and low-cost fix. Or would confirm it's a real fault. But does the replacement ECU have to be retuned to be compatible with my engine? I understand this is a specialist job. Or, as the engines as the same, can it simply be fitted? Any advice gratefully received. Thank you. |
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MGmike
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   Member No: #3151
Location: South Queensferry |
Chris, I'd be very surprised if you have an ECU fault but I suppose it's not impossible. Which Ansel reader are you using as some will not read all the possible Citroen codes. You really need to get a diagbox/lexia on it (or one of the high end aftermarket units like the Ancel v6 Pro). But if you do want to replace the ECU it needs to be coded to match the BSI and other ECU's in the car. I'm not even sure if you can code one that's already been used but others may know. I think you'd need to replace the ECU, BSI, keys and the ignition switch pick-up. Michael |
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onthecut
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 Member No: #2793
Location: West Mids |
Hi Chris. The ECU from another car definitely won't just plug and play, plus - unless you've seen a diagnostic on the replacement piece, you don't know whether it has any issues of its own. Don't forget the absolute basics -- have you checked the condition of the battery and charging system? The fact that the issue went away after a good run may just point at a voltage issue. As MGMike says above, best thing is to get a better diagnostic done. I don't think it's an issue with the C6, but it may also pay to disconnect the ECU and physically check the pins for any sign of corrosion.If you do, don't forget to follow the battery disconnect / reconnect sequences. (Although to be honest, I've never bothered on the various occasions I've disconnected the battery on mine and it's always come back to life just fine). For what it's worth, have never had an issue with the engine ECU on any car I've had. Mike. |
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ChrisW
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Member No: #1335
Location: Surrey |
Hi Michael and Mike Thank you for your replies. It's a very basic Ancel but has served me well in the past and has always identified any limp mode fault. What makes me suspicious of the ECU is that it has at times been impossible to clear the limp mode and it would go into limp with no evidence of a fault and with the engine simply idling. I'm pretty sure it's not the electrics. Both the alternator and battery are fairly new, with no evidence of a fault. The fault appeared at the end of a 200 mile journey, so everything would been fully charged. I have been through the rigmarole of disconnecting the battery and leaving the ECU to discharge overnight. It had no effect. I like the suggestion of checking and cleaning the pins on the ECU because a bad connection could create this type of fault. But, having removed the ECU for this job, I am tempted to try the replacement to see what happens. It is only £60 with a 3 month guarantee. I have contacted the seller to ask if it's a direct replacement without the need for reprogramming. He deals with replacement ECUs and other parts and gets excellent reviews. So I assume he knows his stuff. Also the "breakerlink" website says it can be done and how to do it. If he says yes, I'll give it a try. After all, £60 hardly buys a pub lunch these days! Chris |
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cit-rotti
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Member No: #3753
Location: Bayern |
Good luck then - and please share the result Wolfgang |
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Jas16
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 Member No: #2994
Location: West London |
my car goes into limp mode if the dpf is clogged sufficiently to obstruct high air flow. so as above there are many other reasons that cause the limp mode. looks like you are in surrey, depending where you are, we can use my diagbox as a trial. |
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ChrisW
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Member No: #1335
Location: Surrey |
Thank you Jas for your offer to use your diagbox, much appreciated. At the moment the car is running very well, but I may take you up on it if the problem returns. Re replacing the ECU, the vendor's answer was not very helpful - "if the part numbers match it should work okay but it might need programmed". As everything is fine now, I will not attempt replacement. Thank you everyone for your helpful advice on this. I will keep you posted if there are further developments. Chris |
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