This 2004 Cadillac CTS came in with the complaint of no stoplights. I decided to start by checking the bulbs. To do this I first had to remove the black plastic nuts that also serve as hooks for the cargo net.
After the nuts were removed I pulled the trim panel up that goes across the lower lip of the trunk. This had to be done in order to pull back the side panels.
With the side trim panels pulled loose and out of the way, I could now reach my hand around and remove the two 10 mm nuts that hold the light assemblies in the car.
This is a picture of the holes in the rear fender that the light attaches to. Sorry, there was no room for a picture from the inside.
The studs that attach the light to the car.
The upper socket is for the stoplights and on this car it was grey in color.
If you look closely at the bulb you will see the stoplight element is laying in the bottom of the bulb instead of being attached to the shorter leads.
Another picture of the bulb showing that the shorter or lower element is missing.
The side stoplights were simple enough. Now on to the CHMSL (center high mounted stoplight). I removed the retainers on the left side of the trunk lid trim panel.
Moved the panel out of the way far enough to access the wiring and tested for power on the white wire while the brake pedal was depressed. I had power.
In looking at the wiring diagram I noticed that the CHMSL and the tag lights share a common ground. A quick check of the tag light operation showed that the ground was present in the truck deck lid. Diagnosis of a faulty light assembly. I checked on a replacement light and found that the $668 list price was too much for the customer to handle at this time. I don’t blame them.
Anyways I guess two stoplights are better that none.
