Went to a pressure sensing (MAP) setup instead of a MAF. The ECU was unhappy without the MAF signal so threw a PSM/ABS failure. This is a race car so ABS is a good thing to have in these cars. Had already disabled the PSM so some lights were on but still had ABS with old setup using MAF. Now switch to no MAF. Installed a GT2 pump from an '04+ car (V5.7 so same as TT). There were a couple pinout issues with the left rear wheel sensor, but most else was OK. What I get is an error in the ABS system that it can not communicate with the ECU. The pinouts for Can+ and Can- are correct, and I can communicate to the ABS unit with Durametrics. The ECU has been programmed with the GT2 coding. So actually there are ZERO indicators for PSM that come up now.

Has anyone done this and made the ABS functional? Have tried a couple more things, but car cannot be started at moment. There has to be a simple reason this is not functioning...

 

-Motronic reprogrammed to 2WD, ( or changed to 2WD one )
-ABS/PSM unit wiring changed accordingly
-clutch and brake pedal switches working
-MAF is operational

You have 3 out of 4, and I guess that you're getting the code P5525 ( or was it 5252 )?

I struggled with PSM/Motronic compatibility issues last autumn, and after PSM unit was changed to 4WD one, as the Motronic is, and wiring changed accordingly ( IIRC there's another different pin than LR wheel sensor ), only codes I got were from the MAF. When it was the working, the system also worked. If The MAF is out, so will ABS be too.
ABS/PSM unit can't be programmed, not even with PIWIS.

I'd suggest you to find a Porsche Motorsport ABS unit from a GT3 xx that's running without a MAF. Big $$$ unfortunately.

 

GT2 unit does not care about the MAF. That is why I went to it. So yes I have 3 of your 4 and the 4th is irrelevant now with GT2 ABS pump not the standard TT pump with PSM (about 3/4 the size also). I have no other codes anywhere. The engine codes are fine. Just the ABS cannot commumicate with ECU. Yeah on the left wheel sensor one pin is moved one position, and then the input/output is swapped. Only on that one. Motorsport ABS cant work in these cars without wholesale mods.

So sounds like you went from GT2 to TT????

 

Nope, turbo engine into a C2 with working bells & whistles.

GT2 ABS doesn't care about the MAF, that's interesting...but somehow quite logical if there's no electrical aids.
Difficult to say what's your problem, ABS-Motronic datatransfer has a life of it's own, and those who really know it are very few. If you can loan a GT2 Motronic, try it and see if that cures your problem. While you can't re-program an ABS-unit there might also be something unprogrammable in Motronics too.

 

Motronic has been programmed ala GT2 requirements. That is why looking for anyone who has done this and may know the solution. Thanks though.