Technical ECU swap due to no spark- any way to use a secondhand ECU ?

[richardllew]

Our Mk2 1.2 8v is now firing on 2 cylinders only. The coils are OK, it seems to be the ECU, which appears to be a common problem.
I have another Mk2 1.2 8v, and I tried swapping the ECUs over but the engine code light stays on so there is no spark at all.
Its a bit frustrating having spare parts, but with no interchangeability.

Question ???? Is there a separate immobiliser module as well as an ECU module, and do the modules recognise one another?

I think I will have to fork out £45 or so on eBay for a flashed ECU, but would prefer to get it running temporarily to confirm it's the ECU.

 

[Most Easterly Pandas]

You'll need the key from the donor vehicle of the replacement ECU to deactivate the immobiliser, if you've the locket you could fit this as well, so basically changing the ECU and lock set from the donor vehicle should sort you out

 

[s and b]

hi richard
you dont give much information
please give more and i can help
cars
years
models

 

[richardllew]

Thanks for the replies.

The car thats not working is a 2001 Punto Mk2 1.2 8v and the other car I can swap bits with is a 2000 Punto 1.2 8v. Both cars appear to be the identical.

I've swapped the ECU over and displaced the sender ring from the key barrel so I can use the original key to turn the ignition on but use the key that matches the ECU for the sender ring. This still gives the engine code warning.

What I've done is set up as "Most Easterly " has recommended, but it does not seem to work. To me it looks like there is a separate immobiliser module, but the Haynes manual will never give details on these.

 

[Most Easterly Pandas]

Ah, I'm not sure if you need to replace the body computer also?

TBH s and b is going to be better informed on what to do from here.

 

[a1ant]

Hi mate,

Have you transferred over the BCU from the donor car as well?

The reason the ECU's you buy on ebay are "virginised" is so that they "pair" straight away with the existing BCU. Obviously the one you've taken off the donor car cant do this as its paired to ITS existing BCU.

The code from the key is first read by the BCU before it gives the all clear to the ECU to allow the engine to start. If the two are not paired, it wont give the ECU signal to start.

Alan

 

[s and b]

Hi mate,

Have you transferred over the BCU from the donor car as well?

The reason the ECU's you buy on ebay are "virginised" is so that they "pair" straight away with the existing BCU. Obviously the one you've taken off the donor car cant do this as its paired to ITS existing BCU.

The code from the key is first read by the BCU before it gives the all clear to the ECU to allow the engine to start. If the two are not paired, it wont give the ECU signal to start.

Alan

to add
you must first disconnect battery
you will probably lose radio code too
both cars theoretically have one lambda so what you do is as suggested is body computer/ecu and just to confirm your diagnosis take the key reading ring off the ignition barrel place it on the floor and loosely put the key apllicable into the empty hole and reconect main battery and start car

ignore things like dash flashing and speedo showing 120 miles per hour on test drive as you are only confirming ecu fault

 

[fingers99]

By the by, the sender ring is just a dumb device -- it sends information from the key chip. but does not interpret it.

 

[richardllew]

Thanks for the knowledgeable replies.
I can't find a proper reference to the BCU in the Haynes manual, they keep well away from any security issues, which is not much use when you want to fix a car.
It's pretty clear now that the ECU needs replacing, and I need a virginised one otherwise the immobiliser kicks in.
For future reference where is the BCU located ?

Thanks again, you're a great lot !

 

[a1ant]

Hi mate,

The BCU or Body Control Unit is located on the back of the interior fuse box (the one by your right knee in the Uk). You remove it as one whole unit.

On ebay you will see 2 types of ECU options available.

One being a virginised ECU which will pair with your original BCU one time only.

And a complete ECU + BCU and lock set.

Easiest route is probably the virginised ECU as its basically plug and play.

Alan

 

[maggers]

Yeah, and if you buy a 2nd hand BCU it has to be the same spec. as yours IE 3/5 door etc. So I was told by our local "expert" Fiat breaker anyway.

 

[s and b]

Yeah, and if you buy a 2nd hand BCU it has to be the same spec. as yours IE 3/5 door etc. So I was told by our local "expert" Fiat breaker anyway.

prefer the 'comfort' one myself

 

[Most Easterly Pandas]

BCU - in English / UK / Fiat UK Tech talk is the body computer

 

[RaulCarnahan]

Being someone who has been through this I can say it is the easiest way to get a virginized ECU from ebay.
Make sure you get one thats similar to the existing one as already mentioned. Mine was an M2 something and when I got one that was M3, it didn't work (if you look at the code on the ECU, you'll know what I mean)

 

[richardllew]

It's now fixed !
I got a virginised secondhand ECU from AMS Cars YO8 4BU via eBay. The guy gave good instructions and even gave his mobile number in case there were any problems.
Ordered on Sunday 29th December and arrived Tuesday 31st December, good or what?
The only problem I had was that in swapping stuff round at the hard shoulder of the motorway ( before it was towed off, I even had a spare coil with me) I got the HT leads swapped round. Thankfully I worked this out after a bit of coughing and spluttering, ( the car not me).
As Raul says there are variants of these ECUs which look identical apart from the code label M2 or M3 etc, luckily AMS were clearly advertising different versions which alerted me to this.
AMS Cars say that the main cause of ECU failure is as a result of ignition coil failure. I swapped the rear coil 2 years ago as this was faulty. This was the coil which wasn't being switched by the ECU. I tested the primary resistance of both coils and my spare coil which were identical, but as a precaution I put the spare coil in place of the one which wasn't being switched. Maybe the faulty coil 2 years ago could have weaken the ECU.
Thanks for all your advice.

 

[a1ant]

Hi mate,

Glad it's all sorted, well done!

Alan

 

[s and b]

hi richard you seem a sensible guy
order some ngk plugs for your car via registration number from your factor and fit them soonest
ive had to do 2 ecus this last 4 weeks both down to old plugs

 

[jaydeesq]

It's now fixed !
I got a virginised secondhand ECU from AMS Cars YO8 4BU via eBay. The guy gave good instructions and even gave his mobile number in case there were any problems.

What are the right instructions for replace ecu? needed disconnect battery?

 

[varesecrazy]

What are the right instructions for replace ecu? needed disconnect battery?

Post is 10 years old..

Nobody likely to reply directly.. MEP maybe..

Yes - disconnect the battery before you start