MSPNP2-B8793 - wiring a variable TPS (BMW E34)

Tuning concepts, methods, tips etc.

Moderators: jsmcortina, muythaibxr

Post Reply
Neeek
MS/Extra Newbie
Posts: 4
Joined: Mon Jul 11, 2016 1:23 am

MSPNP2-B8793 - wiring a variable TPS (BMW E34)

Post by Neeek »

Background - have the above MS PNP in a 1989 BMW 535i (manual trans), turbo M30 motor.

The stock TPS on these cars (with manual trans) is a 3-wire affair - idle, WOT and ground, so not variable. These three wires are:

18 - ground
3 - goes to pin 53 on the harness for WOT
2 - goes to pin 52 on the harness for idle

Now, automatic 535i cars have a variable TPS, with 6 wires. These are:

1 - 5v in
2 - ground
3 - signal out
4 - ground
5 - WOT
6 - idle

In wiring up the auto TPS to my manual car (and thus so that MS PNP can get a variable TPS signal), I'm pretty sure I don't want to hook it up like this:

(manual TPS loom --> auto TPS plug)

18 --> 4
3 --> 5
2 --> 6

Because that would basically mean no change, according to the schematic I have of the stock harness. I'm led to believe that the auto TPS should use the other three wires to talk to the MS PNP.

So given that my unit is a PNP and its innards are a mystery to me, I'm left with three wires going into the MS PNP through the factory 55-pin plug (WOT signal, idle signal and ground). Which of the six wires from the auto TPS should I use to connect to the three that feed to the MS PNP?
Neeek
MS/Extra Newbie
Posts: 4
Joined: Mon Jul 11, 2016 1:23 am

Re: MSPNP2-B8793 - wiring a variable TPS (BMW E34)

Post by Neeek »

I may have answered my own question, actually, as I think it's in the documentation that came with the PNP. Should've looked there first!

http://www.megasquirtpnp.com/docs/mspnp ... ?isModel=1

Based on the above:

1 - 5v in -----> Pin 53, WOT, BRN/BLK wire in the BMW harness
2 - ground -----> BRN-ORG in the BMW harness
3 - signal out -----> Pin 52, IDLE, BRN/BLU in the BMW harness
4 - ground
5 - WOT
6 - idle

So 4-6 on the 6-pin plug are not used as these are the non-variable part of the TPS, and 1-3 ARE the variable part; from the factory they go to the auto trans computer first before making their way back to the DME.

At least I think so. Will look to hooking it up over the weekend, but if anyone knows if I'm right or wrong, chime in!
Post Reply