Is the engine control unit for a V90 programmed to the car?

[martin calva]

If the engine control unit in a V90 dies, can a replacement just be dropped in or does it need to be programmed to the car?

Thanks for any information.
Martin

[TonyS9]

I'm not that familiar with the V90, but the later 940s are coded to the key RFID interface (immobiliser that works on the fuel ECU). Although we have had some conflicting results, the volvo data says they are coded and I confirmed this myself, but at least one other person has has some success swapping them over.

Its more the immobiliser is coded to the fuel ECU, but I doubt there is anything else in the car that needs coded to it. There is no CANbus or body computer, its all hardwired. I've transplanted a later 940 system into another car, along with the immobiliser.

In the 940 you just need to get the immobiliser module with ther ECU, or swap the main chip to a non-immobilised firmware.

[martin calva]

Tony. thank you. My reading of your reply is that the ECU probably can't simply be swapped for a good one from another car if it goes bad.

Thanks again,
Martin

[TonyS9]

Well it can (in the 940) if you get the immobiliser module aswell (and ideally the key chips which come out easily).

Do you have a key with a chip in it? They usualy have 2 different colours of plastic and the inner part can be slid out (maybe needs a sharp blade to get it moving).

[Laird Scooby]

In addition to Tonys excellent advice, try to see the donor car running so you know the ECU and alarm/immobiliser modules and fob(s) work.

Are you sure you have an ECU problem?

Often a dead or dyeing battery can cause strange things to happen with the ECU including rough running, cutting out and other wonderful phenomena as can obscure sensors that won't necessarily bring the EML on but can cause problems.

Also a near-death ignition amplifier module can cause cutting out, misfires etc without reporting any faults to the ECU - if you haven't already done it, remove it, clean the back of it and the heatsink with a non-abrasive cleaner (meths, carb cleaner, IPA or similar and polish up with something like Solvol Autosol then apply some fresh heatsink compound and refit.

That may cure the problem i'm guessing you have, assuming you've done the usual checks before coming to the decision the ECU is faulty.

[TonyS9]

The 940 fuel ECU immobiliser isn't anything to with the alarm fob. The alarm is indepenant of the fuel system, it has its own immobiliser for the starter motor.

The RFID chip in the key system works without any buttons, its frictionless as they call it now. But yes it would be nice to see it working before removal.

The RFID module will give a little click (of a relay) when it authorises on ignition on. It then sends some data to the fuel computer and unlocks it. The relay seems to just connect the data line to the ODB connector.

It should be programmable to different key chips, but I've no idea how to do that.

[Laird Scooby]

Originally Posted by TonyS9

The 940 fuel ECU immobiliser isn't anything to with the alarm fob. The alarm is indepenant of the fuel system, it has its own immobiliser for the starter motor.

The RFID chip in the key system works without any buttons, its frictionless as they call it now. But yes it would be nice to see it working before removal.

The RFID module will give a little click (of a relay) when it authorises on ignition on. It then sends some data to the fuel computer and unlocks it. The relay seems to just connect the data line to the ODB connector.

It should be programmable to different key chips, but I've no idea how to do that.

The scenario you hint at there Tony is why i suggested getting the whole shooting match, i know of some cars if one ECU goes down, the ECU, CCU, fob and receiver and key (with built-in transponder) ALL need to be replaced as a matching set. It would also remove any problems of one not being compatible with another through different ages/production times etc.

[martin calva]

My thanks to all for the helpful and informative replies.

The car is running perfectly but, along with some other bits, I have been offered an ECU for the V90 at what seems a very reasonable price.

I was wondering whether it made sense to acquire it and put it in a drawer with the idea that in the event of ECU problems I would then have a spare to try a swap.

But it seems there would be a lot more to it than simply plugging it in to replace the existing ECU so I think my best course would be to pass on its acquisition. But I'd welcome any advice on whether or not it would make sense to add it to my stockpile of parts.

My thanks again for all the very helpful and welcome information.

[Laird Scooby]

Originally Posted by martin calva

My thanks to all for the helpful and informative replies.

The car is running perfectly but, along with some other bits, I have been offered an ECU for the V90 at what seems a very reasonable price.

I was wondering whether it made sense to acquire it and put it in a drawer with the idea that in the event of ECU problems I would then have a spare to try a swap.

But it seems there would be a lot more to it than simply plugging it in to replace the existing ECU so I think my best course would be to pass on its acquisition. But I'd welcome any advice on whether or not it would make sense to add it to my stockpile of parts.

My thanks again for all the very helpful and welcome information.

If you can get the whole set of ECUs including the alarm/immobiliser and fobs, receivers (i'm not wildly familiar with the V90 set up) and whatever else is onvolved so you have the full matched set from just one car, i would say yes.

On older cars such as mine, it's not necessary to do that as the various ECUs aren't coded. However with any that have a linked alarm/immobiliser unit, i would treat them as all being coded and therefore a matched set.

I appreciate what Tony says about them not all being linked and matched but experience on another forum where someone suggested not everything was needed proved that the right course of action was to get the lot, as the recipient found out when he got them on the other side of the planet!

[Rversteeg]

From personal experience I can say that there does not seem to be any link between immobilizer and ECU. The only link seems to be between immobilizer module and the RFID key.
I have exchanged -984 ECU's without a problem. I also tried a different immobilizer with matching RFID key taped to the antenna ring and this also worked fine.