VW Phaeton Stalling: Faulty Start-Stop System Alert

I had a similar issue with my VW Touareg 2009 diesel. Having some experience with VAG diesels, I initially thought it was related to the idle stop system acting up, but it turned out to be more serious. Despite the battery being seemingly fine, my workshop discovered it was actually a battery issue causing the engine stalling. The battery tested OK on basic checks but was heavily discharged and not maintaining proper voltage under load. This affected multiple control units and created unusual system failures, including false eco mode activations. The repair involved: Deep battery testing with specialized equipment, Replacing the battery, Full system reset and control unit adaptation, Clearing all fault codes Total cost was 290€ and the problem never returned. The unusual stalling completely stopped after fixing the battery situation. For better diagnosis, could you share: Current battery voltage readings, Which specific fault codes are stored, Whether the issue occurs more frequently when the engine is cold or warm, If any other electrical systems show unusual behavior, Complete service history regarding the battery and charging system Even with a new battery, there could be charging system problems causing similar symptoms. The alternator or voltage regulator might need checking.

Last service was performed at 64768km just two weeks ago. Thanks for the detailed writeup. I know we ruled out battery issues initially, but your case makes me want to double-check. The fault codes stored are P0380 and P0683, both pointing toward glow plug control module problems. The stalling happens more in warm conditions, especially during city driving when the engine start cycles are frequent. The voltage readings seem normal, 14.2V while running and 12.6V at rest. The audio system occasionally resets itself though, which might indicate an underlying electrical problem as you mentioned. Maybe getting the charging system thoroughly tested would be worthwhile before jumping to replace the glow plug module. How long did your diagnostic process take? Did they find any correlation between the engine stalling and specific driving conditions?

Thanks for sharing those details. Your symptoms sound similar but slightly different from what I experienced. In my Touareg case, the diagnostic process took about 2 days because they wanted to monitor the charging system under various conditions. The automatic restart problems I experienced were mainly happening during slow traffic, but yours showing up more in warm conditions with those specific glow plug codes points in a different direction than my battery issue. The glow plug control module would explain the starter motor struggling and engine start issues, especially with P0380 and P0683 codes present. When mine was properly diagnosed, they found no glow plug related codes at all, it was purely electrical system related. Your voltage readings actually look better than mine were (I was seeing drops to 11.8V at idle). The audio system resets could still indicate voltage fluctuations that regular measurements might miss. However, given your codes and symptom pattern, I would focus on the glow plug system first. With my case, there was a clear correlation between engine stalling and heavy electrical load situations. The workshop confirmed this by running load tests. Since your symptoms seem more tied to operating temperature and have specific glow plug codes, your root cause is likely different from what I dealt with. Would suggest having a proper load test done on the charging system to completely rule out electrical issues, but be prepared that the glow plug control module might need replacement.

The fault codes stored point toward glow plug control module problems, specifically P0380 and P0683. The stalling happens more frequently in warm conditions, particularly during city driving when engine start cycles are frequent. The voltage readings appear normal at 14.2V while running and 12.6V at rest, though the audio system occasionally resets itself. This could indicate an underlying electrical problem as you suggested. Getting the charging system thoroughly tested seems like a good step before replacing the glow plug module. Regarding your diagnostic timeline question, that level of testing would be valuable. The consistent pattern I notice is that the automatic restart problems and stalling occur mainly during warm operating conditions. The start-stop system seems most affected during frequent stop-and-go driving. My voltage readings look solid compared to your former situation with 11.8V drops. However, the audio resets do make me wonder if there are voltage fluctuations that basic measurements might miss. Still, given the specific glow plug codes and symptom pattern, I should probably focus investigation there first while still verifying the charging system is fully healthy. I appreciate the detailed comparison to your case. Even though mine shows some similar traits, the fault codes and temperature correlation suggest a different root cause. I will proceed with load testing the electrical system to rule that out before moving forward with the glow plug control module replacement.