Aftermarket ECU for '97 850 T5 (Wagon)

t5estate · Post by **t5estate** » 02 Oct 2025, 18:42

Ok, so, to start off, I'm the third owner of this specific T5 -- second owner bought it off auction after first owner sold it off. I've had a problem with misfires for a couple months now, and didn't really pay too much mind to it, up until about a couple weeks ago. Check engine light popped on after a while, and the codes showed for a cylinder 3 misfire (earlier codes brought up cylinder 2 (2 codes), and then later on 1+3 (4 codes). Now, I can definitely feel the misfire, and it doesn't help that I have a mysterious oil leak (5 quarts lost in 2 months..). Anyways, I sent it in to a local shop that I trust to take a look at it and diagnose / fix it. They told me that I have an aftermarket ECU (I never knew about it), of which has no visual identifiers. They couldn't figure out what make / model / etc. of ECU it is, and also told me I'm getting a grand total of 103 codes. They said they didn't feel comfortable working on it, and redirected me towards a branch of ipd. The tech that I talked to on the phone told me that he didn't know of any aftermarket ECU's for my specific model. Are there genuinely any ECU's that it could be, or am I cooked, so to speak?

Post by **Sveedy** » 02 Oct 2025, 19:31

I'm going to guess that you have a ECU that was reprogrammed by a tuner at some point in the past.

Post by **matthew1** » 02 Oct 2025, 20:58

Welcome to MVS, t5estate. Look around for a proper ECU. They're very easy to pop in and out. eBay would be where I'd try first.

Post by **erikv11** » 03 Oct 2025, 12:25

What Matt said - get a generic t5 ECU for starters. May not match your emissions setup but sounds like those few codes will be minor.

1997 T5 was Motronic 4.4, the 1996 turbos were Motronic 4.3 so better to *not* get a 96 or earlier ECU.

Post by **matthew1** » 03 Oct 2025, 12:47

Which of these it is I don't know...

https://usparts.volvocars.com/productSe ... l%20module

Post by **Sveedy** » 03 Oct 2025, 13:40

I'd reach out to a tuner first before spending that kind of $$. Might just be a matter of reprogramming it, which would probably be less than $200.
https://www.vasttuning.com/

Post by **scot850** » 03 Oct 2025, 15:03

I like they sell an AWD P80 fuel pump as a complete unit for a reasonable $300 US + shipping. Also an AWD downpipe although I'd need to see if it fits a 19T turbo on a 00 R.

Neil.

Post by **matthew1** » 03 Oct 2025, 15:16

Sveedy wrote: ↑03 Oct 2025, 13:40 I'd reach out to a tuner first before spending that kind of $$. Might just be a matter of reprogramming it, which would probably be less than $200.
https://www.vasttuning.com/

Agreed, for sure don't buy a new $700+ ECU. I posted that link to show part numbers. I should have added a disclaimer

Looks like eBay has 850 ECUs for $50-150ish.

Post by **Chuck W** » 03 Oct 2025, 16:30

erikv11 wrote: ↑03 Oct 2025, 12:25 What Matt said - get a generic t5 ECU for starters. May not match your emissions setup but sounds like those few codes will be minor.

1997 T5 was Motronic 4.4, the 1996 turbos were Motronic 4.3 so better to *not* get a 96 or earlier ECU.

Only the GLT(US) LPT was M4.4 in '97 (Well, for the turbo cars at least) . It however is NOT the same as the 98MY M4.4.

A '97 T5 is M4.3.

aeg · Post by **aeg** » 03 Oct 2025, 16:41

What does it look like under the lid of the ECU box?