Audi Q4 E-tron Brake Pedal Issues Need Fix

Had a similar problem with my 2020 Q4 Sportback e-tron last winter. As someone with some experience working on EVs, I initially thought it was related to worn brake pads, but it turned out to be more complex. The workshop diagnosed an undervoltage issue affecting the brake system electronics, specifically the interface between the hydraulic brakes and regenerative braking system. The squeaky brakes and spongy pedal feel were symptoms of the system not properly managing the transition between regenerative and disc brakes. The fix involved recalibrating the brake system and replacing a faulty voltage regulator. Total cost was 240 Euro, including diagnostic work. Since the repair, the brake pedal feel has returned to normal with no vibration or sponginess. To better assist with your situation, could you provide: Any recent changes in regenerative braking settings? Whether the issue occurs more frequently when the battery is at a specific charge level? If you notice any changes in brake caliper response during cold vs warm weather? Have you checked the brake fluid level recently? These details would help determine if your issue matches what I experienced or if it might be something different with your brake calipers or control module.

Thanks for sharing your experience. After my latest service at 134543km, the workshop performed several tests but found no immediate issues. My brake fluid levels are normal, and there is still plenty of pad material left on the metal brakes. The pedal feedback actually varies depending on the battery charge. When the battery is below 30%, the spongy feeling becomes more noticeable. The regenerative braking seems to engage differently at lower charge levels, affecting how the disc brakes respond. The brake system warning lights remain off, and the stopping power is consistent. Going to schedule another diagnostic check specifically for the brake control module and voltage regulator based on your experience.

Thanks for the additional details about your Q4 e-tron brake system behavior. The correlation between battery charge levels and brake pedal feel strongly suggests this is indeed similar to my previous voltage regulator issue. The brake system in these EVs uses a complex integration between regenerative and traditional metal brakes, controlled by voltage-dependent signals. The symptoms match perfectly, especially the increased sponginess during low battery charge, which is when the system struggles most with managing the transition between regen and hydraulic braking. Since your brake fluid levels and brake pads are good, and given my experience with the identical model, I strongly recommend having the voltage regulator checked. The brake rotors and calipers are likely fine, but the electronic control module might be receiving inconsistent power supply. The repair should be relatively straightforward, similar to my case with the recalibration and regulator replacement. The total cost might have increased slightly since my repair, but it should still be a reasonable fix compared to replacing brake system components. Until you can get it checked, try keeping the battery charge above 40% if possible, as this might help minimize the brake pedal feedback issues. Keep monitoring for any changes in brake system performance or warning lights.

Thanks for the detailed feedback regarding the voltage regulator issue. It helps knowing I am not alone with these symptoms, and the connection to battery charge levels seems to be the key factor in diagnosing the problem. I called the workshop and scheduled a diagnostic check for next week. They confirmed they will specifically examine the voltage regulator and perform a full brake system calibration. The service advisor mentioned they have updated diagnostic software for the brake control module that might help identify any voltage-related issues affecting the hydraulic brakes. The quote for the potential repair including labor and parts is around 290 Euro, which seems reasonable considering the complexity of the integrated brake system. Until then, I will maintain higher battery charge levels as suggested to minimize the spongy pedal feel. Will update once the workshop completes their diagnosis and any necessary repairs to the brake system. Hopefully, a regulator replacement and recalibration will resolve the interference between the regenerative and disc brakes, just as it did in your case.