ECU Swap/Repair 1996 850R

wackenhut · Post by **wackenhut** » 12 Nov 2020, 08:43

If I am having issues starting the car and the last resort is to check the ECU, is this something that can be swapped out without any issues? How do you remove the ECU and where is it located? I was just wondering if an ECU is specific to each car.

Thank you.

yanga001 · Post by **yanga001** » 12 Nov 2020, 08:47

swap is 1:1 for another 850 R Ecu. What issue are you having? (for newer cars it is not 1:1)

yanga001 · Post by **yanga001** » 12 Nov 2020, 09:03

Stupid suggestion as per pm, but did you try replacing the ignition coil? Ive had a v70 that would go from hard cranking to no start since we fried the coil. Replacing it let it start like nothing. If a wire is frayed there (super rare, but your car seems to be a special case) it might not let it start at all although you did mention its a no start so the starter must be going. Only other thing i can think of is a ground fault causing the voltage to drop. Coil could do that or other main power components.

Post by **RickHaleParker** » 12 Nov 2020, 09:08

wackenhut wrote: 12 Nov 2020, 08:43 I was just wondering if an ECU is specific to each car.

Hardware is going to be the same you have M4.3 vs M4.4. The ECU is not tied to the car but there are different versions of software for different configurations.

The ECU/ECM is under the hood, in the black box on the right side. You will need a ECU tool to unlock it from the socket. , or , Remove the sides of the box and slide the locks on both sides with a small screwdriver or something else you can push the locks with.

You can learn a lot at M44 Wiki. Including how to copy and transfer your R software to new hardware.

yanga001 · Post by **yanga001** » 12 Nov 2020, 09:09

I do not think the pre 99's need a tool, i recall they have a switch on them that desockets and slides them out. (might be wrong)

Post by **RickHaleParker** » 12 Nov 2020, 09:18

yanga001 wrote: 12 Nov 2020, 09:09 I do not think the pre 99's need a tool, i recall they have a switch on them that desockets and slides them out. (might be wrong)

Went out and took a peek at my 1998 C70. You are correct the M4.3 & M4.4 have a release lever on each unit. It the ME7 and beyond that need the tool. Guess some CEO at Bosch wanted the cost of the release levers to pay the mortgage on house #3 .

Post by **erikv11** » 12 Nov 2020, 09:57

There is no ECU tool needed (or even produced) for a 96 850. You can swap in any USA market T5 ECU 95-98, it can be an R ECU or not. You may get a CEL for not having matching emissions equipment but it will start the car. I'd get an m4.4 ECU.

To copy and transfer your exact R software to new hardware is not routine at all, I don't suggest getting into that unless you are already skilled at programming. However flashing a spare ECU with a generic R tune is pretty easy. These points can be investigated at the wiki that Rick referred to.

wackenhut · Post by **wackenhut** » 06 Dec 2020, 14:44

Does anyone have a spare ECU that I can put in my 1996 850R to see if that fixes the intermittent no start issue? As long as it is just a quick plug and play replacement to test and see. If it requires any compatibility issues to deal with etc, this option does not make sense.

Thank you.

Post by **Chuck W** » 06 Dec 2020, 15:55

I have a couple '96-'97 "Turbo"/T5 ECUs that will drop in and run your car. (From a '96 or '97 non-R HPT)

wackenhut · Post by **wackenhut** » 06 Dec 2020, 17:34

I would feel more comfortable swapping the same year and “R”.

I have a whole discussion on my car:
Issue with 96 850R Starting Not Turning Over

Just wanted to prepare myself should the positive battery cable replacement not fix the issue.

Thank you.