Hi, I'm trying to gather all and any info for the 89-92 LH 2.4 ECUs used in 200 and 700 series Volvos. From my long search of the archive I found out this:

1. # 0280 000 561 seems to be the original for all '89-90s.
2. # 0280 000 951 seems to replace (improve?) the 561s.
3. Generally the fault rate for (both?) ECUs is much higher than previous and later models.
4. When 561s fails - the car usually won't start (the fault is in the fuel pump relay circuit).
5. The EPROM chip can be replaced with an improved version, fixing... the cold start? Or what?
6. Some suggestions that 561s fail because of bad quality solder (like the fuel pump relays).
7. Confusing info on whether the 561 is the most faulty one or the 951, or both.

Any corrections, additions, suggestions, links to more info, etc. are very welcome.
I also need to find the data that needs to be "burned" to the EPROM chip as it can get corrupted after 13-14 years (from 1989 to 2003...) and also source for the chips or replacements (or at least electronic part ##).

I'm trying to fix my 561 ECU. It died about a week ago by sticking in very rich mode. I was able to borrow a used 951 and the car ran very well with it. Unfortunately I don't have enough even for used ECU at the moment, so the only option is to try to fix the one I have.

If I'm successful in fixing it, I'll post here all steps, procedures and info.

Thanks,
Andrew