Multiple RS4 Systems Down, Clutch Switch Suspected

Had a very similar experience with my 2018 RS5 last winter. Having some experience with electrical issues, I initially thought it was more severe, but it turned out exactly as you suspect. The car stalling and multiple system failures pointed toward a faulty switch, specifically the clutch pedal safety switch that was causing the ignition problem. The gear selector display going dark was the biggest clue, as these systems are interconnected through the safety circuit. Took it to my regular workshop where they found corroded connections at the clutch pedal wiring harness. The whole repair including diagnostics and new parts cost 95 Euro. The mechanic showed me the damaged cables and explained how a single faulty switch can trigger multiple system failures due to the safety interlocks. Before suggesting more specific fixes, could you share: Are there any warning lights on the dash? Does the clutch pedal feel different than usual? Have you noticed any intermittent issues before the complete failure? What engine variant does your RS4 have? Getting these error codes would also help pinpoint if we are dealing with the same root cause.

Thanks for your detailed response. My RS4 is showing those exact same symptoms after 168704 KM. The most recent service was done 4 months ago and everything was perfect until yesterday. To answer your questions: The dash has a flashing engine light and gearbox warning. The clutch pedal feels normal but makes a faint clicking sound when fully pressed. Before the complete electrical fault, the cruise control would out of nowhere disengage for about a week. The car stalling issue matches what you described with the safety switch. My main concern is that replacing just the clutch pedal switch might not solve all these interconnected problems. Though hearing that your repair bill was only 95 Euro gives me hope this wont be a major expense. Would really appreciate if you could share what specific error codes showed up in your case. Just waiting for my code reader to arrive tomorrow to compare.

This definitely reinforces my earlier diagnosis. After experiencing the same issues with my RS5, those symptoms are textbook for a faulty clutch pedal safety switch. The clicking sound you mentioned is particularly telling, I had the exact same noise right before my complete system failure. The error codes in my case were related to the transmission control module and engine management system, specifically pointing to input signal problems from the clutch position sensor. The car stalling was triggered by the safety mechanism not receiving proper clutch pedal position data. Your mileage reading of 168704 KM is actually quite common for these switches to start failing. In my case, the safety switch started acting up around 155000 KM. The unusual cruise control disengagement is also a typical early warning sign, exactly how mine started before the complete failure. The interconnected problems might seem overwhelming, but they all stem from this single faulty switch in the safety circuit. Once replaced, all systems should return to normal, just as they did in my case. The repair itself is straightforward, and the low cost is due to the switch being a relatively inexpensive part. When you get your code readings tomorrow, look specifically for transmission and clutch sensor related codes. These will likely match what I experienced and confirm the diagnosis.

Thanks for the feedback. Just got the error codes and they match exactly what was mentioned, transmission control and engine management errors pointing to the clutch sensor input. The clicking sound at the clutch pedal seems to be the smoking gun here. Given all the matching symptoms, the car stalling issues, and especially the gradual cruise control problems before the complete electrical fault, I feel confident enough now to get this fixed. Will schedule an appointment to replace the clutch pedal safety switch and check the wiring harness for corrosion. Really relieved this is likely just a safety mechanism issue rather than something major with the gear selector or transmission. The 95 Euro repair cost reference helps a lot with setting expectations at the shop. Will update once the repair is done, but based on the shared experience here, replacing that faulty switch should bring all systems back online. Appreciate the detailed help in narrowing this down before heading to the workshop.