VW Touareg ECU Chaos: Multiple Faults Won't Clear

As someone with moderate experience working on VWs, I faced nearly identical issues with my 2016 VW Tiguan 2.0 TSI. The automotive diagnostics showed similar unusual fault codes and active memory problems. The root cause turned out to be undervoltage in the vehicle electrical system at 11.8V, which made the computer system act erratically. Replacing the main ECU would have been overkill and unnecessarily expensive. The solution involved: 1. Testing the battery condition 2. Checking all ground connections 3. Inspecting the alternator output 4. Running a complete electrical system diagnostic The total repair came to 240€, which included: Full system diagnosis, Cleaning corroded ground points, Replacing a faulty voltage regulator, Recalibrating the computer system To help diagnose your specific case, could you share: Current battery voltage readings, Age of the battery, Whether fault codes persist after short or long drives, If there are any other electrical issues like dim lights The car electronics can be sensitive to voltage fluctuations, and storing unusual fault codes is often a symptom of power supply issues rather than an actual ECU failure.

Had my last service done at 93540km. After following your advice, I checked the battery voltage, it reads 11.6V, even lower than what you mentioned. The battery is original from 2014, so that could explain the ECU diagnostics showing these unusual faults. The codes mainly appear after longer drives, and I have noticed slightly dimmer headlights lately. Think I will start with testing the electrical system and replacing the battery before considering the control unit replacement. Seems like a more logical first step, especially given the age of the current battery and the symptoms matching what you described. Has anyone else had success with just a battery replacement solving these computer system glitches?

Thanks for those details. Yes, your 11.6V reading is definitely problematic and eerily similar to what I experienced. After replacing my aged battery, about 90% of the electrical gremlins and fault codes disappeared on my Tiguan. For reference, a proper charging system should maintain: 12.6V with engine off, 13.8-14.4V while running The automotive diagnostics I ran after the battery replacement showed the alternator was actually fine, it was just struggling with an old, weak battery. The repair steps in my case were: 1. New battery installation: 180€ 2. ECU diagnostics reset: 60€ 3. Basic electrical system check: 40€ Total cost came to 280€, which was far cheaper than the 1200€+ quote for an ECU replacement. The fault codes never returned after this fix. Consider having a full charging system test done when fitting the new battery, this can identify if your alternator or voltage regulator need attention too. Since your symptoms (dim lights, codes after long drives) match the classic signs of a failing battery affecting car electronics, starting with the battery replacement seems like the right approach.

You're absolutely right that a new battery makes more sense as the first fix. Just got back from checking the garage down the road, they can fit me in tomorrow for a full electrical system check and battery replacement if needed. The voltage readings really helped explain why my car electronics were acting up. My regular mechanic agreed that 11.6V is way too low for proper ECU operation. He explained how these automotive diagnostics can show misleading fault codes when the power supply is unstable. Makes total sense why the control unit kept recording unusual errors. I am definitely going to skip the expensive ECU replacement for now. Will post an update once I get the results from the electrical system test and possibly new battery installation. Really hoping this solves those persistent fault codes like it did in your case. The repair costs you shared also seem much more reasonable than the 1200€ estimate I got earlier. Has anyone else used a specific battery brand that works particularly well with these VW systems?