RS4 Electrical Gremlins Point to Failing Auxiliary System

Recently dealt with similar auxiliary battery issues on my 2017 RS4. The symptoms matched exactly, error messages, weak starts and inconsistent electrical behavior despite a healthy main battery. The auxiliary power system had degraded, causing power management issues throughout the vehicle. The auxiliary battery provides backup power for various control modules and electronic systems while the engine is off, so when it fails, multiple systems get affected. The fix required: Complete diagnosis of the power management system, Replacement of the auxiliary battery, Recalibration of the battery monitoring system, Software update for the power management module This was not a minor issue since the auxiliary battery malfunction can potentially affect critical systems like start-stop functionality and basic electronics. The degraded auxiliary battery was causing voltage fluctuations that confused various control modules. Would definitely recommend getting the auxiliary battery tested first. These symptoms typically indicate auxiliary power issues rather than main battery problems. The auxiliary battery often fails earlier than the main one due to constant drain from modern electronics. This type of electrical system diagnosis requires proper diagnostic equipment to accurately assess the power management system and auxiliary components.

Thanks for sharing your experience with auxiliary battery failure. I had pretty much identical issues with my 2020 RS4 last year, constant error messages and weak starts despite having a good main battery. Had it fixed and the car has been running perfectly since. Curious how the repair costs compared, my auxiliary battery replacement plus the system diagnostics and recalibration came to 450 Euro. Did you end up having any other electrical gremlins pop up after getting it fixed? The battery malfunction really had me worried about potential long-term damage to other systems. Still keeping an eye on my voltage readings just to catch any early warning signs of low voltage issues. Worth being cautious with these complex power management systems.

After fixing the auxiliary battery malfunction at the shop, my RS4 has been running flawlessly with no electrical issues. The total repair cost was 290 Euro, which covered the battery replacement, diagnostics, and system recalibration, quite a bit less than what you paid. The voltage drop problems completely disappeared after the repair. No additional electrical gremlins have surfaced in the car electronics since the fix. The engine start is strong and consistent now, and all those annoying error messages are gone. Smart move monitoring your voltage readings. Regular checks of the auxiliary battery can help catch potential issues early. Modern car electronics are quite sensitive to power fluctuations, but once properly addressed, the system usually remains stable. The battery replacement solved all the problems in my case, and the power management system has been working as intended. No lingering effects or damage to other components, which was also one of my concerns initially.

I took my RS4 to a different mechanic this time and had a much better experience. They immediately diagnosed the auxiliary battery issue using proper diagnostic equipment, something my previous shop missed completely. The technician found the voltage drop was indeed coming from a failing auxiliary battery. The replacement process went smoothly, including a full power management system check and recalibration. The whole job took about 2 hours. Total cost was 380 Euro, which seems reasonable compared to other quotes. Most importantly, the electrical gremlins are completely gone now. No more error messages, the engine starts perfectly, and all systems are working as they should. Really glad I switched mechanics. The new shop clearly understood modern vehicle electronics and power management systems. They even showed me how to monitor for early warning signs of low voltage issues in the future. Going to stick with this shop from now on. Worth every cent to have the problem properly diagnosed and fixed rather than continuing to chase electrical ghosts.