Audi S5 Cruise Control Failure Linked to Faulty Sensors

Had exactly this issue on my 2020 Audi S4 with the same 3.0L engine. The cruise control suddenly stopped working and displayed error messages on the dash. After troubleshooting, the root cause was a faulty brake pedal switch that incorrectly signaled the brake was engaged. The cruise control system constantly thought the brakes were being applied, causing it to disengage. The steering wheel controls appeared functional but would not activate the system. The repair involved testing the pedal switch connections and replacing the complete brake pedal switch assembly. The speed sensor and other components tested fine. This was not a major repair in terms of complexity, but proper diagnostic equipment was essential to pinpoint the exact issue. Important to note that a bad throttle position sensor typically causes additional symptoms like rough idle or inconsistent acceleration, which were not mentioned in your case. The isolated cruise control failure points more toward the brake pedal switch based on these symptoms. Would recommend having a certified shop check the brake pedal switch and its wiring connections first before exploring other components. The diagnostic process needs specialized equipment to properly test the cruise control system inputs.

Had exactly this issue on my 2020 Audi S4 with the same 3.0L engine. The cruise control suddenly stopped working and displayed error messages on the dash. After troubleshooting, the root cause was a faulty brake pedal switch that incorrectly signaled the brake was engaged. The cruise control system constantly thought the brakes were being applied, causing it to disengage. The steering wheel controls appeared functional but would not activate the system. The repair involved testing the pedal switch connections and replacing the complete brake pedal switch assembly. The speed sensor and other components tested fine. This was not a major repair in terms of complexity, but proper diagnostic equipment was essential to pinpoint the exact issue. Important to note that a bad throttle position sensor typically causes additional symptoms like rough idle or inconsistent acceleration, which were not mentioned in your case. The isolated cruise control failure points more toward the brake pedal switch based on these symptoms. Would recommend having a certified shop check the brake pedal switch and its wiring connections first before exploring other components. The diagnostic process needs specialized equipment to properly test the cruise control system inputs.

Thanks for the detailed response on the brake pedal switch issue. Good to know it wasnt a major repair, my first thought was it would need the whole throttle position system replaced which had me worried. I noticed the cruise control behaves exactly as you described, with the steering wheel buttons appearing normal but the system refusing to engage. Would you mind sharing what the repair ended up costing? Also curious if you encountered any other related issues since getting it fixed? My local shop does have the right diagnostic tools but they seemed unsure about testing the brake light switch connections properly. Might need to find a more specialized place for this.

Thanks for the detailed response on the brake pedal switch issue. Good to know it wasnt a major repair, my first thought was it would need the whole throttle position system replaced which had me worried. I noticed the cruise control behaves exactly as you described, with the steering wheel buttons appearing normal but the system refusing to engage. Would you mind sharing what the repair ended up costing? Also curious if you encountered any other related issues since getting it fixed? My local shop does have the right diagnostic tools but they seemed unsure about testing the brake light switch connections properly. Might need to find a more specialized place for this.

Just had the cruise control issue resolved last week, you were spot on about the brake pedal switch being the culprit. The total repair came to 95 Euro, which covered fixing a damaged cable connection at the brake light switch assembly. The steering wheel controls now work perfectly with no error codes. Since the repair, the cruise control has been functioning flawlessly. No other related problems have surfaced. The key was finding a shop that properly diagnosed the connection between the brake light switch and the cruise control system. They found a loose connection that was causing intermittent signals to the cruise control module. The speed sensor and other components checked out fine during testing. Make sure wherever you take it can properly test the fuse box and wiring connections, a blown fuse wasnt the problem in my case, but its often overlooked during initial diagnosis. Definitely worth getting it checked by a shop that specializes in electronic diagnostics. The brake pedal switch is a common failure point in these systems, but proper testing equipment is essential to confirm the exact issue.

Just had the cruise control issue resolved last week, you were spot on about the brake pedal switch being the culprit. The total repair came to 95 Euro, which covered fixing a damaged cable connection at the brake light switch assembly. The steering wheel controls now work perfectly with no error codes. Since the repair, the cruise control has been functioning flawlessly. No other related problems have surfaced. The key was finding a shop that properly diagnosed the connection between the brake light switch and the cruise control system. They found a loose connection that was causing intermittent signals to the cruise control module. The speed sensor and other components checked out fine during testing. Make sure wherever you take it can properly test the fuse box and wiring connections, a blown fuse wasnt the problem in my case, but its often overlooked during initial diagnosis. Definitely worth getting it checked by a shop that specializes in electronic diagnostics. The brake pedal switch is a common failure point in these systems, but proper testing equipment is essential to confirm the exact issue.

Thanks for the input. Finally got my cruise control fixed and wanted to share the outcome. Took it to a certified shop specializing in electronics and diagnostics. They immediately focused on testing the brake pedal switch connections like suggested here. Turns out there was a failing clock spring causing intermittent connectivity issues with the steering wheel controls. Also found a loose connection in the fuse box that was contributing to the problem. The dashboard light would out of nowhere flash when the cruise control failed. Total repair cost was 280 Euro including parts and labor. The shop was thorough and showed me exactly what was wrong. Been driving for a week now with zero issues, cruise control works perfectly and no more error codes on the dash. Really glad I found a better shop this time. Their diagnostic equipment picked up the issue right away compared to the first place that seemed lost. Definitely worth paying a bit more for proper service.

Thanks for the input. Finally got my cruise control fixed and wanted to share the outcome. Took it to a certified shop specializing in electronics and diagnostics. They immediately focused on testing the brake pedal switch connections like suggested here. Turns out there was a failing clock spring causing intermittent connectivity issues with the steering wheel controls. Also found a loose connection in the fuse box that was contributing to the problem. The dashboard light would out of nowhere flash when the cruise control failed. Total repair cost was 280 Euro including parts and labor. The shop was thorough and showed me exactly what was wrong. Been driving for a week now with zero issues, cruise control works perfectly and no more error codes on the dash. Really glad I found a better shop this time. Their diagnostic equipment picked up the issue right away compared to the first place that seemed lost. Definitely worth paying a bit more for proper service.