Freddybob
TYF Newbie
- Joined
- Jul 14, 2025
- Posts
- 2
- Reaction score
- 0
I have an 04 Suburban 2500 with an 8.1 that until recently had a strange problem with the cruise control. I spent forever tracking down the actual problem and wanted to share what I found to hopefully help someone else.
I replaced my hydroboost because of a hydraulic leak and then all the problems started. I didn't have any codes, but the cruise control didn't work. Brake lights worked, trailer lights worked, but when viewing the data from the TAC module on a Tech2 I couldn't see the "Cruise Release Brake Pedal" show as "Activated" (meaning the pedal press wasn't being registered), but the Stoplamp Pedal Switch signal did work.
I followed the troubleshooting guide and verified connectivity in the circuits between the pedal, tac module, ecu, and ebcm. I replaced the brake light switch twice, and even replaced the TAC module.
In desperation, I decided to remove the brake pedal switch and activate it with a screwdriver while viewing the data on the Tech2. Low and behold, the cruise release showed Activated! I assumed that the brake light switch wasn't being actuated far enough by the pushrod from the booster, and turns out, that was the case.
Shimming the end of the pushrod runs the risk of bottoming out the switch or engaging the brakes, neither of which I wanted to do. Instead, I took apart the switch (just four clips, pretty easy) and discovered the center circuit (the one that carries the cruise release signal) was not opening unless the switch travel was nearly maxed out.
I ended up being able to put a piece of rubber tubing (windshield washer to be exact) around the middle post on the lever to fill the gap between the post and contact blade so that it opens immediately. This simple fix resolved my issues, and the cruise control works again!
Now with the rubber in there, the cruise release circuit opens while the PCM circuit does and just prior to the physical brake lights come on which is the behavior that I would expect.
I replaced my hydroboost because of a hydraulic leak and then all the problems started. I didn't have any codes, but the cruise control didn't work. Brake lights worked, trailer lights worked, but when viewing the data from the TAC module on a Tech2 I couldn't see the "Cruise Release Brake Pedal" show as "Activated" (meaning the pedal press wasn't being registered), but the Stoplamp Pedal Switch signal did work.
I followed the troubleshooting guide and verified connectivity in the circuits between the pedal, tac module, ecu, and ebcm. I replaced the brake light switch twice, and even replaced the TAC module.
In desperation, I decided to remove the brake pedal switch and activate it with a screwdriver while viewing the data on the Tech2. Low and behold, the cruise release showed Activated! I assumed that the brake light switch wasn't being actuated far enough by the pushrod from the booster, and turns out, that was the case.
Shimming the end of the pushrod runs the risk of bottoming out the switch or engaging the brakes, neither of which I wanted to do. Instead, I took apart the switch (just four clips, pretty easy) and discovered the center circuit (the one that carries the cruise release signal) was not opening unless the switch travel was nearly maxed out.
I ended up being able to put a piece of rubber tubing (windshield washer to be exact) around the middle post on the lever to fill the gap between the post and contact blade so that it opens immediately. This simple fix resolved my issues, and the cruise control works again!
Now with the rubber in there, the cruise release circuit opens while the PCM circuit does and just prior to the physical brake lights come on which is the behavior that I would expect.
