Swapping Multiplex Ecu's On Later Psa Models

[Anthony 1,003]

A colleague at work is having no end of problems with his Phase 2 Xsara VTS ever since jump starting it, and is convinced (although I am not) that it is an ECU fault caused by a spike from jump starting. Possible, but seems unlikely, given that the engine does start and run briefly.

 

I've got a spare ECU from a Phase 2 Xsara VTS that I broke last month and was going to give it to him to try on his car and see if it fixes the problem.

 

The only thing that I'm not sure about given that the Phase 2 VTS's are multiplex is whether it's as simple as just swapping the ECU's over, as it would be on the earlier Phase 1 VTS's and most other Peugeot and Citroen models late 90's and earlier that have conventional wiring and independant ECU's. On those, you'd just go through the unlock procedure (if it has an immobiliser on the ECU), swap the ECU over, start it up and job's a good 'un.

 

Is it that easy on Phase 2 VTS's and other multiplex wiring models, or as I suspect do you have to get the ECU coded in some way so that it will talk to the rest of the devices connected to the multiplex wiring?

[S@m 156]

A colleague at work is having no end of problems with his Phase 2 Xsara VTS ever since jump starting it, and is convinced (although I am not) that it is an ECU fault caused by a spike from jump starting. Possible, but seems unlikely, given that the engine does start and run briefly.

 

I've got a spare ECU from a Phase 2 Xsara VTS that I broke last month and was going to give it to him to try on his car and see if it fixes the problem.

 

The only thing that I'm not sure about given that the Phase 2 VTS's are multiplex is whether it's as simple as just swapping the ECU's over, as it would be on the earlier Phase 1 VTS's and most other Peugeot and Citroen models late 90's and earlier that have conventional wiring and independant ECU's. On those, you'd just go through the unlock procedure (if it has an immobiliser on the ECU), swap the ECU over, start it up and job's a good 'un.

 

Is it that easy on Phase 2 VTS's and other multiplex wiring models, or as I suspect do you have to get the ECU coded in some way so that it will talk to the rest of the devices connected to the multiplex wiring?

 

I believe the ECU's are matched to the BSI, so require coding. A good way to check is look up the ECU on servicebox and see if there is a coded/uncoded part number. Failing that i can check myself in work on monday.

 

Sam

[Alastairh 47]

I am fairly sure it needs coding etc £££'s.

[Rob Turbo 3]

What exactly are the problems he's having?

 

BSI's are known for throwing wobblies after being jump started.

[jackherer 543]

First dibs on the rear beam

[Redtop 14 2 Cars]

Im away at the min, but a fella that comes into my work works on older vehicles and he uses somewhere in england to wipe the ecu, so he can start again and just code the thing straight in again with his diagnostic software. I must ask and see if he can get me any more details on this for you. Mind you most of the stuff he works on is diesel but can't see this being any different.

[Anthony 1,003]

Thanks for the info - sounds like my suspicions were right and it's not a simple swap, but rather ballache and expense.

 

What exactly are the problems he's having?

From what he's said (as I've not seen it) the engine very reluctant to start, and when it does eventually fire, doesn't run particularly well and cuts out after 20-30 seconds or so, refusing to restart again.

 

Sounds far more to me like something like the MAP sensor has failed and the fuelling is all over the place, and that it's probably more likely that something has failed or suffered damp where the car stood for a few weeks (hence the battery going flat) and it's just coincidence with the jump start.

 

Personally, I'd expect a knackered ECU to just not start or to have a very definite hard fault with it.

 

First dibs on the rear beam

You'd be onto a winner as I only rebuilt it for him earlier this year.

 

I feel it's probably good manners that I wait at least a week or two before circling around it like a vulture and offer buy it to break for parts though

[S@m 156]

Heres something i ripped from the dealers xsara workshop manual taht might be relevant;

 

It is necessary to reinitialise the engine ECU, after any of the following operations :

 

* Clearing of the faults

* Disconnection or replacement of the ECU

* Disconnection or replacement of the battery

* Disconnection of the ECU supply relay(s)

* Downloading a program to the ECU

* Replacement of the idle regulation stepper motor

* Replacement of the throttle potentiometer

 

Failure to reinitialise the engine ECU, after any of the above operations, will cause the following driving defects :

 

* Engine hesitation

* Engine cuts out when returning to idle

* The engine stalls on starting

 

----

The procedures for reinitialising it all involve the dealer diagnostic tool but i believe theres another way of doing it; think i saw it on the xsara forum. Oh and i checked, you definetly can't just swap the ECU's over wihout coding.

 

Sam

[Anthony 1,003]

Thanks for that Sam

 

If I'm reading that correctly though, that sounds utterly ridiculous that you potentially need to take the car to a dealer/specialist for mundane stuff like swapping a battery - I would have expected something similar to the earlier GTi-6's where the ECU reverts back to an "unlearned" setup and then re-learns by itself after a few minutes running. What you've put above seems to imply that rather than doing it automatically, you need to force the ECU to do it on the later cars by plugging it into the diagnostics...

 

Christ I'm glad that I drive older cars without any of that nonsense if that's the case!

[S@m 156]

Here is the topic on the xsara forum about how to reset the ECU;

http://www.cxoc.net/index.php?topic=5774.0

 

Although, there seems to be some disagreement on how to do it exactly.

It does imply that you need a dealer for simple operations, but from a manufacturers point of view thats fantastic! (bastards!) Multiplexing does seem to have more pitfalls than advantages imho. Im terrified of doing anything electrical on my xsara - even fitting a new headunit is 10x more complicated than the old 306!

 

Sam

Edited September 5, 2011 by Sam306

[smithy 1]

That's the way Many pugs ecu's were reset

Battery disconnected for a while so settings lost then reconnected,start engine with lights,fan rear screen heater going then leave to idle until fan kicks in.

Then it needs 45 mins driving,15 mins at high revs,15 mins at speed on motorway and then 15 mins round town at different speeds and loads.

Pug used to call it the rally method made a massive difference to drivability of the non multiplex,it was hit and miss on multiplex if it don't work it needs to go on diag2000

[pug_ham 245 3 Cars]

As mentioned by Rob above, jump starting the car can cause issues with the BSI, iirc when you jump start the car you should put an electric load on (ie; heated rear window or fan) before you disconnect the jump leads due to voltage spikes upsetting them or something.

 

g

[sickomotorsport 4 2 Cars]

i take it you have put it on diagnostic machine? if not this is first port of call, also if the engine ecu is at fault you can replace the bsi,key and ecu all out of the same car and this will work and wont need coding.