David_UM

I have a 98 TA body, with a 99+ PCM and harness. Body harness is still a 98. The car was also a4 but is now T56 swapped. Complicated I know lol.

I recently finished this T56 and harness swap as the 98 harness was chewed up and in bad condition. I spliced and wired all the C plug connections needed to make it work inside the cabin.

The issue is that I cannot crank the motor with the key, but if I manually jump the starter, the car will turn on

I have swapped the starter and ignition relay. Iginition switch was swapped over about a year ago so it’s still brand new. I have also bypassed the clutch switch with the green and purple wire so the clutch does not have to be pressed to start. Furthermore, I have also grounded the 12th yellow and black wire on the BCM to ground for start, just to rule out a bad Module. Nothing.

I can hear the fuel pump cycle on so I know it isn’t a VATS issue, I also have HPtuners so I turned that off years ago.

Lastly, I turned off the theft deterrent system just in case it was alarm based still nothing.

Any suggestions would be appreciated.

JimTA

iTrader: (10)

Have you checked your starter relay trigger? With an auto it runs through the VSS, how are you triggerjng now? So yellow from ignition switch through 15a starter fuse to VSS(purple/white) i think then dk green is output to relay. The yellow black is ground side of that relay...

David_UM

Yes, the relay is good.
I actually don’t know how I’m triggering it now? How is it supposed to be with a manual? I just have it wired up through the pcm directly to the VSS as I have a m6 harness.

JimTA

iTrader: (10)

Not sure on manual but guessing a wire from clutch switch to relay. Keeps from starting if clutch not depressed. Relay probably has 4 wires.. battery voltage, output to s terminal on starter, the little terminal, purple wire I think the the wire that grounds one terminal, this is the black/yellow circuit wire you grounded then 12v trigger from clutch switch. Check purple wire when key is in start or you should hear relay click I would think if triggered.

JimTA

iTrader: (10)

And sorry meant NSS neutral safety switch.. either my fat fingers or android thought it new better

David_UM

Got it. I’ll do that tonight and report tomorrow

JimTA

iTrader: (10)

I am at my computer now so easier to explain. Good hunting
here is the starting diagram for my 2002.. Assuming it is same for your 99 harness (LS)..
the purple boxes are the points I would be checking
since you replaced all the parts in the circuit I would start with finding that Neutral Safety switch (3) and make sure it hooks to clutch start switch.
If that is good check
1 - Yellow wire should have 12V with key in crank position only this 12V comes through ignition switch so radio and other stuff works you are probably good there.
2- The same ignition circuit feeds the start relay so probably good there
3 - this is where yellow 12V and 15A starter fuse feed through the clutch switch giving the relay power. This is my guess where your issue is
4 - Normally the BCM would ground this terminal based on VATS to let Relay start car. In your case you have already grounded, but check at relay to be it is...
5 - if point 3 has 12v and point 4 is grounded when in crank you should see 12v here if yes then there is a problem in your purple wire (because you can jump the terminals on starter it sounds like starter is good)

David_UM

Ok, so I get nothing at point 3 which is the green wire

On the starter relay, I get signal at all points except pin 85

David_UM

And purple wire gets 12v when cranked!

JimTA

iTrader: (10)

Then your problem must be in the purple wire between relay and starter... That shouldn't be too bad.

David_UM

Ok Jim, let me run this by you from the beginning because I think I might have confused both of us on accident, My bad not yours!

Ill use this diagram just cause its a litte easier to explain.

1. I get 12v from the yellow wire to the mini fuse which than powers the purple/wht wire that leads to inside the cabin. Awesome.
2. PPL/WHT wire, is than hard wired to the DK Green wire which than leads to the starter relay under the hood and leads to pin 85 on the relay.
3. On the relay Pin 86 is grounded and i get a signal, pin 30 is power and constant and there is power when checked. When pin 87 and 30 are jumped, the starter engages, therefore confirming the purple wire to the starter is in fact working.
4. Pin 85 on the relay is supposed to be 12v, since it is the PPL/WHT and DK green wire which are connected, at this pin I get no signal

This is where I currently am.

JimTA

iTrader: (10)

so sounds like your pin 85 is not getting 12V? you get 12V at yellow wire but is the fuse good and sending voltage on purple/white? Sounds like you are close now at least.. if pin 86 is grounded and jumping 30 and 87 cranks can't be any more than the relay bad or fuse/wire bad i would think... i believe the fuel pump relay and others are same.. you might swap one real quick just to see.

David_UM

I'm completely stumped. Fuse is good I had spares. And yes, ppl/wht wire is getting 12v. I tried rigging pin 85 with 12 and still nothing

JimTA

iTrader: (10)

Swap relay with fuel pump relay. Make sure you have good ground in yellow black... Easy for me to say 😉.