OBD2 Aba swap woes, cranks but no spark or fuel...

[tgibson]

Posting this up for a buddy. We're in the process of an aba swap in his 90 Jetta, and it's gone seemingly well until this point.

We bypassed the starter interlock, and we can get the car to crank with the key. We have the main red power wire plugged into 30 and 30B using the mk3 red jumper piece.

Because the swap is OBD2 we've read that we don't need the #32 relay (position 3) for the ecu power. Having it in or not makes no difference.

The problem is not the ecu, we've tried multiple ones. I keep hearing about some mythical wire that if i don't give 12v the ecu won't power up.

The car will crank and crank but never show any sign of the ecu getting power. No spark or fuel. What are we missing?

[tgibson]

No ones had this issue?

[tgibson]

This is the best part of searching btw...

[unfamousk]

BUMP out of curiousity....doing the same swap and agree searching is useless when all photos are outdated and broken links

[Sputterputz]

When you turn the key on, can you hear the throttle body humming? If not, you are not getting power to the ECU,

Have you checked your pins on the ECU?

Pin 01 Gound - Brown/Red
Pin 23 SW 12v- Black/yellow
Pin 54 12v C - Red
Pin 56 Ground - Brown/black

If you have those, your ecu will power up. if youre missing one, its not going to... after that, youll need power for the coil, and fuel injectors/TB/sensors ect... but all of that comes off the body harness and doesnt run to the ECU...

Have you looked over a2 resource ? all your questions are answered in those diagrams...

[tgibson]

I think we were on a2 resource for 6 hours yesterday...

The throttle body does it's little clickity calibration thing when we turn the key. So the ecu is getting power?

As for the body harness powering everything. Would something with that explain why the fuel pump doesn't prime/ do anything? We don't have spark either, which is what it confusing.

The ecu has power, but does nothing. So what are we missing?

[tgibson]

We don't have a ground at pin 56 at thr ecu plug. Could this cause the no fuel or spark? Also where does it lead to, we're untaping and following it now...

[Sputterputz]

Make sure the power supplied via the switched power stays present during cranking.

That 56 went to either the fuseblock ground or directly to the battery -.

[tgibson]

Success

We followed that wire for forever and said screw it, so we just spliced in another ground to it. Car fired on the first try.

I would be a hypocrite now if I didn't post some final answers, so I'll take some pictures of how the fuse box is set up to hopefully help some future people out.

[Sputterputz]

Good deal!!

[Greg_J]

bump because i turned up in the search result picture