Right rear lights situation Help Please

[TimMcC]

Hi, I have a 2008 GMC Sierra 2500 HD 4x4 Duramax and my brake light, blinker and running light on the rear passenger side is not working. The back up lights work. I have checked all fuses, replaced all the bulbs, replaced the rear wiring module and the harness from the module to the right tail light. All this is done and I have the same results. So when I turn the right signal on, it flashes 3 times normal and then hyper speed after that. have check to see if there is any voltage running to the harness and it is a little bit less than the driver side. I have heard there is a relay under the dash that might fix it. But I can not find that. I have ordered a new brake pedal switch, the cruise does not always work either, and read this could make the tail lights act funny too. Thoughts?
Thank you

 

[2004LB7]

brake pedal switch would be my guess or a bad ground at the rear light circuit. the BCM does all the switching so there is no relays in line that could fail. also the wrong bulbs can do that too

 

[TimMcC]

brake pedal switch would be my guess or a bad ground at the rear light circuit. the BCM does all the switching so there is no relays in line that could fail. also the wrong bulbs can do that too

I have tried several different bulbs, even the ones from the drivers side, no of them work in the passenger side.
I just replaced the Brake pedal switch... no change.
Where would this rear light circuit be hiding?

 

[2004LB7]

 

[2004LB7]

 

[TimMcC]

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Thank you for this. This is the module I replaced. Perhaps I need to clean all the connections and put some electro grease in each one. This is frustrating beyond!

 

[TimMcC]

So I cleaned the module and all harnesses with electroclean and then greased with dielectric grease. Found a blown light in the 3rd eye on top the cab, replaced it and everything is working the exact same. The brake pedal switch fixed the cruise control though. So does anyone else have any information that might fix this?

 

[1FastBrick]

Usually that stupid junction block module has an internal problem.

If you replaced it with a known good one or new one one and it didn't fix it , Then I Wonder if the issue is with the BCM???

 

[TimMcC]

So I cleaned the module and all harnesses with electroclean and then greased with dielectric grease. Found a blown light in the 3rd eye on top the cab, replaced it and everything is working the exact same. The brake pedal switch fixed the cruise control though. So does anyone else have any information that might fix this?

Just pulled out the seats and checked the SDM Airbag module. Very clean no corrosion, sprayed them and greased them. Same problems are occurring. Could this be a bad BCM???

 

[TimMcC]

Usually that stupid junction block module has an internal problem.

If you replaced it with a known good one or new one one and it didn't fix it , Then I Wonder if the issue is with the BCM???

That was my next question. Perhaps a BCM. Well Ill try that and see. Thank you

 

[Ron Nielson]

Tim
With electrical problems, you need to get your test light and DVM out and find out where the problem is. No one can tell you where you have a broken wire, short, corrosion, bad ground, bad pin fitment, etc.

 

[2004LB7]

^^^ yep. as Ron said. I have provided the electrical diagrams and connector pinouts. now it's up to you to probe them and see where you are and are not getting proper voltage. I'd measure it right at the BCM, then at the next connection until you find the issue. if the voltage is low at the BCM then you found your problem. if it good then it is in the harness or connection somewhere and we can't do much from here to help you find it. if you can't figure it out then maybe it's better to take it into a shop and have them fix it