2008 GMC Sierra Denali, Multiple Electrical Problems

This 2008 GMC Sierra Denali came in with multiple electrical complaints. The blower did not work. The left side stoplight, all left side turn signals, the right side mirror turn indicator. All of the power windows except for the right rear window did not work. There were a multitude of codes scattered through various modules. Most were stored in the DDM and the PDM. I did some testing of various circuits and decided there must be a problem with some of the major power supply fuses.

The 40 amp Blower fuse at position #70 was blown.


The 60 amp LBEC2 fuse at position #72 was also blown.


The underhood fuse box legend


Some of the testing that lead me to the underhood fuse box was the fact that all of the fuses in the row I am pointing to with my test light were unpowered even with the ignition on.


The driver’s side fuse box legend.


It took a little bit of looking around but I found where the wires were shorting out above the parking brake assembly.


A little bit better view of the shorted wiring harness.



A clear view of the shorted out wires with the harness tape pulled back.


In the end I had to cut and splice one of the wires back together. The other two only had the insulation slightly damaged so I wrapped them with live rubber tape. Wrapped that with regular electrical tape. Wrapped the wiring harness back up where the tape had previously been removed then covered all of that with some large split loom. I also reformed the harness to stay away from the parking brake assembly.


I found it easier to work by removing the under dash panel on the driver’s side of the truck. There is a 10 mm headed bolt that holds the parking brake release handle in place.


Once the bolt was removed the handle assembly had to be slid towards the firewall in order to disengage the hooks.


There are two phillip’s headed screws along the lower edge of the panel that have to be removed. One at either corner.


Then the panel can be pulled from the dash by pulling it towards the seat. That will disengage the retaining clips.


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