Expert: Rob Painter - 4/6/2011

Question
I its me with the electrical problems with the cadillac, the orginal problem was when i remove the head unit one all or one of of three wires touched the 12v constant, the car was at accessory, he smoke came out of the ipc none of the lights worked on the ipc only the speedo and tach, thats why i replaced the ipc, after replacement the change trans fluid message came on and wont reset, RAP, turnsignals, and the fuel gauge do not work, the fuel gangue moves a little bit upon start up but only to the bottom of the E

Answer
Hi,

Sounds like you have a real mess there. You still have not said as to why you removed the head unit in the first place.

Whenever electrical issues are being performed other than checking circuits, the battery needs to be disconnected.

I have no idea what else you burned up, hence the cascading effect. You could have burned up the bcm (computer) and if you replace that, something else may burn it up again if you don't physically check all wiring. Even the manual is limited to help you there for diagnostics when you are dealing with burned out electronics you can run into the vicious cycle.

Hopefully you did not burn up the wiring as well. Once there is smoke, there should be a very severe concern. When dealing with a short circuit, which obviously you had with power to ground, all bets are off. Not only do you fry the electronics, but the wiring as well. It takes a nano second to melt the insulation off the wiring and if power and ground are arced together, you can have a fire. If two power wires are melted together, then you have a feed back situation that can blow out the electronics.

You are now looking at a tremendous amount of work checking everything just to prevent a fire, much less saving the electronics.
I will tell you, if I had to repair this car, it would be on an open ticket with no estimate. Look, I am not criticizing you for trying to save yourself some money, but there are some things that cost the owner far more when trying to fix their car themselves, especially in the blind with no meter, no service manual. There are far too many electronics in these cars to make a mistake with.

This is what I would do if I were working on this car. I would disconnect the battery. I would remove not only the IPC, but the dash as well.

I would check all the wiring. Every bit of it for melted insulation. You have the manual now and you need to check the wiring with an ohm meter for the fuel gauge, the trans fluid change light circuit, Rap and what ever else you are dealing with.

There is the possibility that you burned up the fuel tank sending unit which is part of the fuel pump in the tank or the wiring leading to it.

It is possible that the electronics might be OK and that you have wires fused together. Right now, you don't know what you have until you physically check all the wiring.

If you continue to replace parts, you are not going to fix anything. You will not find any diagnostic chart that will consider the situation you have, because once there is smoke connecting something all bets are off!

After you physically check ALL wiring in the dash and you need to hope that is the only place you may find burned wiring because electricity flows to the location of least resistance. I would, if I were you, install a different BCM and IPC after confirming you have no melted wiring. If you are lucky, this will get you fixed. Then reconnect the battery and see what you have.


I would not use the IPC you have right now because there could be internal problems in the electronics and the same goes with the BCM.

Good luck and let me know what you find.

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