changed synergie ecu now wont start

parksy · Post by **parksy** » 04 Aug 2010, 19:27

i have a citroen synergie and also have my old peugeot 806 as a spare, my ecu needed replacing so i used the one from the pug! worked great after it was changed, left it for a couple of hours and went to go out and it wouldnt start......keep trying but it wont do anything it turns over but will not start, does anybody have any ideas as to what i have to do. thanks

khand · Post by **khand** » 04 Aug 2010, 21:31

Put it back on 806 and see if it works on that? (Still)
What RP nos' are we talking about?
Keypad immobiliser or chip key?

Regards

Kevin

wheeler · Post by **wheeler** » 04 Aug 2010, 21:31

You dont say what year both cars are or if they have a keypad imobiliser or transponder. Generaly Ecu's are not interchangeable on modern cars without changing a few other bits & pieces. It probably started initially because the ecu would have been unlocked depending on how soon it was disconected off the other car after switching the ignition off, after the ignition has been switched off for a few minutes then tried to restart the codes on the ECU wouldnt have matched the imobiliser code hence the now non starting. Are you sure the original ECU was the fault ??

parksy · Post by **parksy** » 04 Aug 2010, 23:34

right...... the 806 is a 1998 the synergie is a 1999.....they are both chip immobilisers and both ecu's have the same code....would using the chip from the 806 key solve this problem?? the citroen ran really lumpy...missfiring on cylinders 2-3....replaced coil pack plugs and leads with brand new but no different......ran perfectly when the 806 ecu went in so i thought great but now refuses to start!!

wheeler · Post by **wheeler** » 05 Aug 2010, 16:31

You would also need to swap the CPH unit from the other car as well as the keys. The ECU, CPH & keys are all matched to each other.
I cant remember the exact location of the CPH on the synergie/806 but it's behind the dash, It's a small black box about half the size of the ECU with a yellow and a black plug

This is a pic of one here but a bit of the plastic has been cut away around the plugs.

parksy · Post by **parksy** » 05 Aug 2010, 19:39

yeah he got that and the bit around the barrel plus the other key but it still wont start..................if we put the old ecu back in it starts fine but misses terribly................i was just wondering if maybee there is something we missed replacing when we were trying to figure out why it was missing, does anybody have any ideas why it was missing so badly that dont involve the ecu???.............or maybee we did fix the missing with the new coil pack but the ecu remembered that something was wrong so it has stopped firing on those two cylinders to avoid damage and now the ecu needs resetting?????.......really dont know what else to do i'm confusing myself now!!! haha

Post by **CitroJim** » 05 Aug 2010, 21:15

With the old ECU in and the engine running, is the engine management light on?

parksy · Post by **parksy** » 05 Aug 2010, 22:00

yes the engine management light is on with the origional ecu in situe

Post by **CitroJim** » 05 Aug 2010, 22:06

parksy wrote:yes the engine management light is on with the origional ecu in situe

Best you get a Lexia diagnostic carried out to see why. There are manifold reasons why it might be on and it's impossible to guess why without diagnostics. There's a good few of us here with a Lexia and hopefully one of us is near you...

parksy · Post by **parksy** » 05 Aug 2010, 22:13

ok will try to find someone with diagnostics thanks for your help