M20 cold start relay mod

Post Mon Jul 14, 2014 7:17 pm

Can anyone help with how the wiring is done.

We used to have a diagram but can't find it and forgotten how to do it. Its been a few years

Looked in wiki but no help really with the wiring up

Cheers

Post Tue Jul 15, 2014 11:56 am

As far as I know this was only required on the 073 ECU and was a bodge that didn't work very well.

Get a 173 ECU. It's a straight swap and works a lot better.

Ben

Post Tue Jul 15, 2014 7:32 pm

cool thanks i have a look for one tomorrow

Post Wed Jul 16, 2014 11:59 am

073 for 173 ECU requires an engine harness change ! not a plug and play swap !

Post Thu Jul 17, 2014 1:54 pm

Sorry about that.

Was going by memory rather then checking.

My 1989 manual cab came with a 164 (not 073) ECU and had the cold start bodge fitted by BMW.

I swapped it for a 173 and stripped out the bodge wiring and it was fine.

Strange that the wiki says a 164 is for automatics.

Ben

Post Thu Jul 17, 2014 2:16 pm

The 163/164 ECUs were an early version of Motronic 1.3, but had twin PCBs, as per the earlier Motronic 1.0/1.1 ECUs.

They also don't work with the later Motronic 1.3 chips.