[Joe1217]

Today I took my 03 CTS to the shop for new tires and alignment. I had no problems leaving the shop but after my first stop I could not get it to shift out of park and none of the brake lights were working. I was able to open the shifter boot and manually disengage the lock and drive home. I researched forums and tried most of the recommended fixes with no luck, so any input would be greatly appreciated. So far I have tried: checking ohms on the brake light switch and the cruise control switch closed and open (they both seem to be functioning fine), Checked all fuses in the rear fuse panel and disconnected battery. I don't have a code scanner on hand, but I'm not getting any warning lights on the dash. I will try and get it scanned tomorrow.

Thanks!

Joe H.

 

[ngoodnight01]

Looks like the RIM fuse and the IGN 3 fuse in the rear fuse block control the shift interlock check those

 

[MsMac]

Good morning.
I am by no means a mechanic or now anything about auto repair but...I had the same issues with my CTS. I went to a shop that did a few tests and took out a small black box from under the dash on the drivers side. The signal lights are now working. Oh let me also say that I had changed the bulbs - still nothing so i replaced the entire light assembly trying to fix myself! I now have a left & right tail light assembly that is not broken and sitting in a box! I am going back to the shop on my next day off so the shift issue can be fixed. I have to put the key in and press the brake pedal before turning the key then it shifts no problem. The technician told me what the name of the part was but...I forgot. It has to do with some part by the brake pedal why the shift won't dis-engage. My issues were running lights/fog lights, brake light, turn signal, front headlight, shift from park to reverse/drive. Little things but it's frustrating and can be costly!
Good luck - let me know if this helps at all.
Denver