No power to CAB

Tiny
WILLIAM WARNER
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 195,000 MILES
My gauges all quit working except speedometer and tachometer. The 4x4 switch won't light up, dome light won't work, windows, door locks, cruise control, A/C, rear defrost all don't work. Took it to a shop to have it scanned and won't communicate with anything. Replaced BCM and no difference. Checked all grounds and cleaned them. Any help would be appreciated.
Wednesday, February 12th, 2020 AT 7:18 AM

7 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Good morning,

Did the shop test for voltage to the fuse block under the hood? It sounds like there is not power coming from the fuse block to the accessories.

Roy
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Wednesday, February 12th, 2020 AT 8:34 AM
Tiny
WILLIAM WARNER
  • MEMBER
  • 4 POSTS
There is power everywhere, all fuses are good also.
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Wednesday, February 12th, 2020 AT 8:54 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
When you replaced the BCM, was it new and did you have it flashed to your VIN?

The BCM does control most of those functions.

Beyond that, you have a wiring issue somewhere.

Roy
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Wednesday, February 12th, 2020 AT 9:16 AM
Tiny
WILLIAM WARNER
  • MEMBER
  • 4 POSTS
Yes, I had it flashed to my VIN. Doesn't make sense of why a scanner can't communicate with anything.
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Wednesday, February 12th, 2020 AT 9:18 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Was there power to the data link connector? Did the shop verify that?
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Wednesday, February 12th, 2020 AT 9:20 AM
Tiny
WILLIAM WARNER
  • MEMBER
  • 4 POSTS
Yes there is power to it.
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Wednesday, February 12th, 2020 AT 9:21 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
Okay, back to power. Did the shop check for powers to the modules? The ECM would be the first one to check.

Does the check engine light come on with the key in the on position?

I attached the powers and grounds to the ECM to be checked. Check those pins for power and the grounds as well.

https://www.2carpros.com/articles/how-to-check-wiring

Roy
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Wednesday, February 12th, 2020 AT 9:30 AM

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