Question on MIL light

[Sdannenberg3]

Cannot find the answer to my specific question and it's a long shot here, but I figure i'll try.

E36 BMW LS swapped, with HP tuners. What I want t know is, is my MIL light now controlled ONLY by the GM PCM? or can the BMW chassis computer still throw DTC that cause the MIL to be on?

In case specifics are needed, when I read the DTC with HP Tuners, I get P1637 which seems to be something with the Alternator. I checked the tune thats on the PCM and it has code P1637 set to not report error. Clear the DTC codes and engine light stays on. Check again and it's code P1637 again. NOW, BMW has a code P1637 as well, and its related to throttle blade position sensor or something to that nature. So could the chassis computer be throwing that code (for obvious reasons) and then HP tuners is just reading that code? Or is the Camaro computer that came with the ls1 I bought the only thing that controls the MIL light?

[cobaltssoverbooster]

i dont know exactly what your asking here.
if you connect to the ls ecu and use the hpt scanner to read codes then the codes you receive are for the gm ecu.

[Sdannenberg3]

Hey! thanks for the reply

Right, I cannot read any BMW codes from HPtuners connected to the GM ecu.
What I am asking then, is can anything else (like the BMW chassis computer) cause the check engine light to come on? Or is the check engine light ONLY being controlled by the gm ecu?

[5FDP]

If the GM computer is standalone from the BMW harness and cluster the GM computer can not make the check engine light come on.

If you wired the check engine light in the cluster to the wiring harness for the GM computer/OBD2 port then it's likely to show up.

[Sdannenberg3]

The wire harness was built by wiring specialties. So it has everything to run the LS standalone, with the GM ecu. But It also does hook up to a connector that ties into the BMW chassis harness. So the GM ecu can send info to the dash. So my speedo and tach work, off the gm ecu.

And in HP tuners, if I manually turn the MIL off, it turns off. Unhighlight off, and its back on again. Just trying to see if there is any other system, like a BMW chassis computer that could still possibly be (also) making my check engine light stay on, because I've set the tune up to not report the code P1637, which is the only code that pops up when I scan DTC with hp tuners, and I clear the code, and it keeps coming back and my light stays on.

[Sdannenberg3]

Im having a hard time explaining what im asking.. Maybe this is a better way to ask...

The Check Engine light should only be physically wired up and controlled to one computer. Like either the stock BMW ecu with the stock engine, OR the GM ecu and engine that I now have in it correct? And there shouldn't be another system in the car (like the ones that control the other stuff like windows, door locks, air bags, ABS, etc) to be able to possibly make that light turn on?

[cobaltssoverbooster]

you would have to verify the gm harness is terminated on the pin that signals the engine light.
once you find out which one is pinned to the light you know which one is making the light come on.

[QTR FMS]

its only gm ecu that is throwing code i dont think bmw have body module on e36,

how do you have your alternator wired?

[Sdannenberg3]

Ok, so it is only the GM ecu throwing the code. So I did test and told the tune to ignore code P1637 and reflashed and check engine light went off. So all is well there. Turned it back on and now time to fix the problem in the first place.

I have the exciter wire plugged into the 4 pin plug on the back. This was done by wiring specialties, so hopefully its right. The battery is charging. But the positive lead is going right to the starter. Can grab a picture in a bit.