Nothing works inside the car except for the windows power button and mirror adjuster

Tiny
TGEILING
  • MEMBER
  • 2005 PONTIAC GRAND PRIX
  • 2.4L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 165,000 MILES
My car starts runs great! Horn honking, hazards flashing, windshield wipers going crazy, headlights stay on won't shut off. Nothing works inside the car except for the windows power button and mirror adjuster. No radio, instrument panel, air or heat or information center. Has anybody had this problem? I had to pull the fuses to stop the horn and wipers.
Please help. Thank you
Saturday, June 18th, 2022 AT 1:23 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

It sounds like an issue with the body control module. However, that is a theory at this point.

Here is what we need to do. If I was to try and direct you, it would be a guess and not a good way to diagnose. What you really need to have the can-bus needs scanned.

CAN stands for controller area network. Basically, all the different computers/modules are tied together via a few wires. They use these few wires to communicate back and forth.

If you have the can-bus scanned, it will identify diagnostic trouble codes regardless of the module storing them. This will point us in the right direction for diagnostics and repair.

Here is a link that shows how it's done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

It really isn't difficult to do, but it does require a scan tool with the capabilities.

If possible, have this done, and let me know what codes are retrieved. That way I'll know how best to help you.

Let me know what you find.

Take care,

Joe
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Sunday, June 19th, 2022 AT 9:15 PM
Tiny
TGEILING
  • MEMBER
  • 3 POSTS
Hi Joe, I have absolutely no power on the inside of the car. It starts and runs great, my lights, horn, windshield wipers and hazards stay on. I pulled the fuses for the horn and the wipers.
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Monday, June 27th, 2022 AT 3:57 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

If you have no power to the inside fuse box, there are three fuses to check under the hood. I suspect two are good because you mentioned the horn and wiper fuses had to be removed.

If you look below, I attached the wiring schematic. I highlighted the wires between the under-hood fuse box and the interior fuse box. Check the three fuses I circled.

Let me know what you find.

Joe
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Monday, June 27th, 2022 AT 8:42 PM
Tiny
TGEILING
  • MEMBER
  • 3 POSTS
Hi Joe, I tested all fuses inside and out! They are all good. :(
would the ignition switch cause these problems?
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Sunday, July 3rd, 2022 AT 7:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

Something has likely shorted in the Body Control Module (BCM). That is a theory based on the need to remove the fuses for the horn and wipers.

We have two ways to approach this. My first suspect is the body control module has failed. You could replace the BCM and hope I'm right (which I don't want to do) or we can scan what is called the can-bus.

CAN stands for controller area network. Basically, the different computers/modules in the vehicle are tied together via a few wires and communicate with each other.

A traditional scan tool wouldn't read these codes, so a scan tool having the ability to read the can-bus is needed. If there is an issue with the BCM, there should be a code identifying an issue. Here is a link that explains how it's done.

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

I don't know if you have one or access to one, but this is what I would suggest. Regardless, let me know your thoughts and I will do my best to help.

Take care and Happy 4th of July.

Joe
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Sunday, July 3rd, 2022 AT 8:23 PM

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