Audi Q5 Battery Issues Trigger Multiple Error Codes

Had similar issues with my 2018 Audi Q7 diesel when the auxiliary battery started failing. The symptoms match exactly what you describe, error messages, difficult cold starts, and car electronics acting unpredictably. The auxiliary battery supports various electronic control units and comfort functions while the main battery handles starting. When the auxiliary battery malfunctions, it creates cascading issues throughout the electrical system. My car showed multiple stored error codes related to voltage drops. The workshop diagnostic confirmed low voltage readings from the auxiliary battery. The problem required: Full electronic system diagnosis, Auxiliary battery replacement, Battery control module reset, System adaptation This was a serious issue requiring immediate attention since failing auxiliary batteries can lead to unexpected electrical system shutdowns and potential safety concerns. The repair was complex due to the need to properly integrate the new battery with vehicle systems. Recommend checking both batteries voltage levels first. If auxiliary battery shows less than 12V when measured, it likely needs replacement. Best to have this done at a shop familiar with Audi electrical systems due to the programming requirements. The symptoms will only get worse if left unaddressed, potentially affecting critical car electronics and control modules. Based on your mileage, this timing for auxiliary battery replacement is quite typical.

Wow, thanks for the detailed response on my Audi power management issues. The symptoms you described match mine perfectly, those unusual error messages and voltage drop warnings are really concerning. The auxiliary battery replacement sounds like the most likely fix based on what you explained. Got a couple quick follow-ups: Do you remember roughly what you paid for the full repair including diagnosis? Also curious if youve had any similar battery malfunction issues since getting it fixed?

Since having the auxiliary battery malfunction fixed on my Q7, the electrical system has been running perfectly with zero issues. The repair shop found the low voltage problem was indeed caused by a failing auxiliary battery, just as suspected. The total cost came to 290 Euro which covered the complete diagnosis, new battery installation, and all the necessary programming to integrate it with the power management system. The investment was worth it since proper auxiliary power is critical for modern Audis with their complex electronics. The engine start issues and unusual error messages completely disappeared after the repair. This kind of battery failure is pretty common at higher mileage, but once properly fixed, the system should work reliably for years. My suggestion would be to get it checked soon, as leaving a weak auxiliary battery can potentially damage other electrical components. The battery malfunction symptoms you described are textbook indicators that its time for replacement.

Thanks for the input. Just wanted to close the loop on my Audi electrical problems. Finally got it fixed last week and wanted to share my experience. Took it to a specialized Audi shop after getting those insights about the auxiliary battery. The diagnostic confirmed low voltage issues stemming from a failing auxiliary battery. The car electronics were going haywire because of the power management problems. The total repair came to 310 Euro including: Full system diagnosis, New auxiliary battery, Programming and adaptation, Battery control module reset. Been a week now and all the error messages are gone. Cold starts are strong again and no more battery malfunction warnings. The shop explained these auxiliary power issues are common in newer Audis with lots of electronics. Really glad I got this sorted before it caused damage to other systems. The car feels like new again and all electrical functions are working perfectly. Definitely worth the investment to fix it properly.