I have a B5254T engine with a T5 ECU (without immobilizer).

My car does not either have immobilizer.

I found a 850R ECU on ebay and got it home. When I try this ECU the car fires up, but dies after a second. I suspect this new ECU to have a immobilizer firmware and is awaiting signal that running is allowed.

Does anyone know if this behaviour is correct if the ECU is missing immobilizer signal?

Is there any way to bypass or fool this new ECU to make my car start?
Some say it's only a 12v signal to the ECU, but in the wire-schematics I cannot find which one. I find a white wire which goes from a original immobilizer to the ECU (B36) and also to the autotrans and OBD connectors.

sounds about right. i was told that you cannot mix ecu's and the motors not intended to run with them. this is a prime example of why. plus no telling what other incompadible issues you will have. one big problem with swapping motors is correctly matching the ecu and main harness, plus it has to program harmony with the trans computer for proper signals and reactions. the emobilizer is the start of your problems. you may be able to flash the ecu to bypass the emobilizer, or get complete wire diagram for both the specific year and make of the ecu donor and you current 850's wire diagram, you canthen figure out what wire ports coincide with the nessasary sensors or relays you need the signals from. possible to mimick the signal you need. anything is possible.

This is probably another one of those areas where there are differences in opinion.

I have been using an OBD1 ECU for quite some time now, without much issues. I have even been swapping the ECUs over and over, just for the fun of it.

And a buddy of mine has been purchasing and trying on ECUs of many-many-many other cars as well. None with much issues. Most of which he secured from the scrap yard, so we have NO IDEA if the car was actually running with immos or not to begin with. Even with that kind of risk-taking, very-very few (like 1 or 2 of the many ECUs that he bought) are totally useless.

By useless, i mean drivability is a concern. No boost, etc. But in all of the ECUs, the car would start as normal!

I dont know if that would give you any added information.

Cheers.

I contacted Bosch and got comfirmed that my ECU had an immobilizer enabled firmware.

Also today I'm using a T5 ECU on my 5254T engine without any issues. This engine is supposed to have another ECU with Motronic 4.4 firmware. But I have changed the wire harness to match the ECU.

The 850R ECU is also using Motronic 4.3 firmware and should indeed be able to run with the same engine and harness I'm using today.

But then the immobilizer signal is missing the ECU shuts down. I've studied the wire diagrams but cannot find a voltage input. Google doesn't either provide any information about communication between the immobilizer and the ECU.

I have found a immobilizer kit that was in sale from Volvo earlier. The volvo part number is 3474024 and may be compatible with the ECU. Called Volvo today, but they could not confirm this.

Aaaah, that explains it.
THe immo function is the culprit, then.

Try calling Bosch and see if they can help.
They SHOULD be able to at least pass you something that is already printed or so, right? Unless they are lazy, like some of the sales people i know around me here. Hehe.

[quote=kjetil,Sep 9 2008, 09:50 AM]"I'm using a T5 ECU on my 5254T engine without any issues. This engine is supposed to have another ECU with Motronic 4.4 firmware."
" I have changed the wire harness to match the ECU." 
[right][snapback]91307[/snapback][/right]
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:thumbsup: aahaa.....
"The 850R ECU is also using Motronic 4.3 firmware and should indeed be able to run with the same engine and harness I'm using today." yes, and the 4.4 is just updated firmware of the 4.3......

[right][snapback]91307[/snapback][/right]
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yes, and the 4.4 is just updated firmware of the 4.3......

exactly.......
and bear, yes i see the room for opinion, im not sure of the related ecu's you guys may have swapped in the present, or past, but i stood at the parts counter at volvo and asked about mixing breeds (ecu- motor- tcm- trans). It is theory that this is not a "good" idea due to performance issues, smog levels, and complete harmony of all nessasary functions needed for satisfactory performance. Thats where I drew arguement of the same nature, but it makes sense, are you completely sure you are getting 100% true performance, not just motor and feel, but all workings under the powers of the ecu? unless youve measured every connection, every signal, every pulse, then you will see why they refrain from endorsing ecu and powerplant mixing.
desired performance and saying your problem free is purely opinion, if it feels great it must be good right? wrong. things prove out in the long run, and unless your a scientist on the board of volvo design, you wouldnt pinn you problems on the true source, we as consumers dont have the technology. :thumbsup:
but who are we to conform, right? just look at our 850's :thumbsup:

Bosch is telling that there's no way to go around the immobilizer function. The only way is to get the immoblilizer that's supposed to operate with this ECU (from the same car).....

All hope is out for this ECU I think.

Does pulling any of the immobilizer fuses make any difference?

no. the american issued 850 was in series. 93's dont work with 94's or later, 94's dont work with any other year, most 95-97.5's will interact if your lucky and match according to options and close manufacturing dates.
Pulling the fuses or relays is the equivilent of hot wiring or tampering with the ignition, this is how the ecu will identify any obscure actions and will not function.
Really, this is bad news even for me. Ive found that you cant get around total rebuilding your own powerplants for absolute trouble free situations like this. The ideas of the 850 was so new to volvo back then, they changed things drasticly, even more so for the not so forgiving american markets and guidelines. want a new world of power? try a canadian model, even more differnt, but closer to e-spec numbers and right over the toll borders, but, they dont operate with our emmissions and smog standards. GO GREEN! :thumbsup:

:grin:

I thought the main idea was just to see if it works. :)
I mean, i agree with you. In fact, a properly tuned ECU would need to incorporate all the neccessary 'inputs' when programming. And as such, when swapped to another car that doesnt have the components, the performance inevitably would not be the same. Granted. I agree with that 100%. No qualms.

But if he wanted to know if the ECU can be used. THe answer is still a YES.
:)
Unless of course, the fault or damage lies with the ECU itself.

Cheers, bro.

Well, that adds another entry into my "Bad things about immos" book.
:grin:

... actually thats not true lah.
:)

:haha: :thumbsup:
well, mabey this guy should just try another ECU? or mabey get the alarm module from the car he got the ecu from? Stick a fork in that one, its dead. :clap:

Maybe chipping this ECU will erase the immobilizer function. Anyone knows if this immobilizer function is hw or sw (chip) ?

To get the original immobilizer I think may be difficult. The ECU is from Spain (ebay). I live in Norway.... :-)

Yeah, i guess its as good as so, bro.

:clap: