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

[Laird Scooby]

Originally Posted by 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.

That is almost the same advice offered on the other forum i mentioned Rob, granted it's a different car but who really knows exactly how Volvo configured them?

While my approach may cost a bit more to start with, having the full set from a working car should guarantee any future ECU faults can be overcome, whether they happen to be linked or not.

[TonyS9]

Originally Posted by 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.

Did you confirm the immobiliser function actually worked without the RFID chip?

To clarify to others, I assume you mean no "coded" link. There is of course a data link between the reader and the ECU.

I feel we should try to replicate this.

Anyone have a spare reader? or 96 on car in NI?

[Piet22]

The Volvo documentation (TP3604031) says that the immo control unit is locked onto a specific type of ECM and not to a specific unit.
This suggests it should be possible to swap ECM's of the same type.

[Rversteeg]

Did you confirm the immobiliser function actually worked without the RFID chip?

To clarify to others, I assume you mean no "coded" link. There is of course a data link between the reader and the ECU.

No, the immobiliser function does NOT work without the right RFID chip / key. Therefore the immobiliser module (reader) and RFID chip are coded together.
Appearently there is no such coding between immo module and ECU.
I cannot confirm what Piet suggests, but as far as I know the -984 ECU is the only one with an immobiliser function.

When you start, the ECU sends a signal to the immo module (reader). The module checks if the RFID chip is present near the antenna ring. If so, it returns a signal to the ECU which releases the fuel pump. I do not know what kind of signal there is sent between reader and ECU, but it is not an individually coded signal as suggested by the Volvo literature.

[Piet22]

Link to relevant pages in TP3604031:

https://www.pscvdplas.com/s/CFFdjwBr222BvUm

https://www.pscvdplas.com/s/HmOce4LsYEkM8fG

With "type of ECM" I think Volvo means either LH 2.4.4. (940) or Motronic 4.4 (960/X90)

[loki_the_glt]

I have successfully swapped out the orange immobiliser relay for another one after the immobiliser decided to stay immobilised. I still have the original relay, but it's sitting in the passenger door pocket these days...

[Rversteeg]

The immobiliser I am referring to with RFID chip in the key does not have an orange relay. The immobiliser communicates directly with the chip in the ECU.
The immobiliser unit itself is black and has the size and shape of a cigarette package.

[TonyS9]

Originally Posted by loki_the_glt

I have successfully swapped out the orange immobiliser relay for another one after the immobiliser decided to stay immobilised. I still have the original relay, but it's sitting in the passenger door pocket these days...

Thats the alarm/immobiliser, they arn't coded to anything except the alarm fob. Immobiliser works on the starter motor. You can just pull it out and bypass it easily. Having said that 96-on ones are harder to get to, but could be bypassed with a wire in the engine bay.

The Key chip immobiliser we are talking about, actually immobilises the Fuel management ECU and is fitted to 96 on 940s. To bypass it you need to change the chip in the ECU or fit an older ECU. This is Thatcham grade security (locking bracket for the ECU and connector is also part of it). The engine won't start without the key with an authorised chip in it (similar to a swipe card).

[Rversteeg]

The Key chip immobiliser we are talking about, actually immobilises the Fuel management ECU and is fitted to 96 on 940s. To bypass it you need to change the chip in the ECU or fit an older ECU. This is Thatcham grade security (locking bracket for the ECU and connector is also part of it). The engine won't start without the key with an authorised chip in it (similar to a swipe card).

If your immobiliser fails, on first try the engine will still start and pick up for one or two seconds and then die. Maybe it will do the same on second try, but as the fuel pump is not running it will only crank and certainly not pick up anymore on a third try. All the time you will see the MIL on, even during the short running period. Funny thing is that during such an immo failure a Volvo OBD scanner can only access the LH, not the EZK.