Electrical issue - things work for 4 seconds after I release brake pedal

[rpeter46]

I have a 2003 Tahoe with approx 140k on the clock. I just isolated a large parasitic battery drain to the instrument cluster(fairly common). While the cluster is out of the vehicle being repaired, I still have another electrical issue. Here is a list of items that DO NOT WORK unless I press the brake pedal:

-entire radio system
-window controls from driver's seat(they work from the individual doors, but not from driver's controls
-engine temp gage, charging gage, oil pressure gage
-backup lights(all other lights seems normally operative)
-push-button 4x4 switches

When I press the brake pedal, all these systems work properly for approximately 4 seconds, then quit working again. Does anyone know of a some common short that might be causing these syptoms? Am I losing my ground on a circuit? Thanks for any good advice...

 

[rpeter46]

I was hoping someone with experience might be able to make some suggestions.

I went ahead and did some exploring- I found that when I remove the connector from the brake pedal switch, everything comes on as it should! I immediately ordered an OEM switch from the dealer and installed it. The issue remains-I thought it may have been a switch with a short in it. Any ideas where to check next? Pull Taillights and look for missing grounds??

 

[Doubeleive]

ya I would start at the tail light's and look for anything there otherwise that sounds like a serious ground problem and you may be able to trace it from the brake pedal harness with a meter.
one question though how old is the battery? and have you checked the battery terminals?
second question how do know the gauges are not working if the cluster is out?

 

[Kraig]

Check your grounds—seems like maybe something is backfeeding

 

[rpeter46]

ya I would start at the tail light's and look for anything there otherwise that sounds like a serious ground problem and you may be able to trace it from the brake pedal harness with a meter.
one question though how old is the battery? and have you checked the battery terminals?
second question how do know the gauges are not working if the cluster is out?

Thanks for the response. I know the gauges were not working before I pulled it. I have since replaced the gauge cluster after getting it rebuilt. Symptoms are unchanged as original posting

 

[rpeter46]

Check your grounds—seems like maybe something is backfeeding

SOOO many places to check grounds, right? I guess start with the taillights? Unless you all can point out another common suspect to check first. Isn't there a harness under the driver seat that is suspect?

 

[rpeter46]

I went through the brake lights, and pulled the module that breaks out the taillight wire harnesses and mounts onto the body. It is bolted to the body underneath the Rear A/C unit on the passengers side. I pulled all plugs, cleaned and lubricated contacts with CRC contact cleaner. In addition, I turned on the ignition and cranked up the radio as I wiggled wiring from one end of the vehicle to the other-hoping if there was a loose connection I would find it. No dice yet.

 

[ncalvo]

I had a bad parasitic drain on my 2003 tahoe at 145k miles. It took me a while of doing things before I noticed it was fixed.

My car was always dead, but a new alternator and new battery helped.
Sometimes my right blinker would come on solid when I stepped on the brake.
Sometimes my dash cluster would peg both ways and flash warnings.
My headunit would not turn off when I took the key out of the ignition, and it would stay on until the battery was depleted.

I added a battery disconnect switch to prevent draining. Cleaning and tightening the terminals helped.
I also pulled the fuse for my radio, and with out power to my radio I have not had a single problem anymore.
My 8 year old 7" pioneer dvd head unit must be the issue and I plan to replace it soon. Until then I drive around without audio - it's better than a dead car.

Everything functions normally again. Interestingly enough, I tried to pop the radio fuse back in to see if I could get some music for a 1 hour drive I was making - as soon as I put it in my dash cluster pegged both ways and gave me crazy warnings and said unknown driver, etc. Again, the head unit stayed on even with the key out.

I am happy to be past these electrical problems, and I hope when I re-do my sound system I don't experience any of these weird issues again.

good luck!