MikeSwidz Posted February 21 Share Posted February 21 My AUDI A8 (Diesel) has experienced several random but immediate engine shut downs at town driving speed resulting from sudden and unexpected RED "Drive System Fault/Fail" warnings flashing up. This has now occurred 4 times in as many weeks. The car is booked in for a diagnostics check with Audi. Fortunately all the faults and engine stops have occurred at relatively low speed. However, as the engine cuts out immediately there is no chance to pull over safely and I have caused traffic to back up as a result of the occasional mid-road "breakdown". The engine restarts almost immediately after stopping and the RED fault light clears. No other warning lights come up prior to the RED warning. The fault has so far not occurred at motorway driving speed - and I hope it does not given that the engine shuts off immediately. The car is regularly serviced by AUDI and no modifications have been made. I have been using the same fuel and fuel stations that I have done since buying the car from new in 2019. What is odd is that the warnings appear to be clearing and not showing up on the car warning and information log NOR on the myAUDI app. Any ideas/suggestions? Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted February 21 Author Share Posted February 21 Yes, it's an Audi A8 V6 50 TDI - first registered July 2019. As mentioned, there is nothing showing up on the cat fault log history that I can access as driver. Would the OBD codes show up during the car diagnostics check? Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted February 22 Author Share Posted February 22 Hi Jason, a follow-up to your Waste Gate Actuator fault suggestion: 1. So far the RED Drive System fail/fault and engine shut-off has only occurred at low town driving speed. 2. I did however follow up on your Waste Gate Actuator suggestion. I did a self test by trying to rev the engine hard in neutral. Interestingly the engine refused to rev past 2500 RPM. Not sure if this is by Audi design or whether indeed there is a fault with the Waste Gate Actuator or Turbo System. 3. No warning signs come up when I try to rev the engine hard - just the limitation of RPM to around 2500 RPM. Car goes into Audi garage for diagnostics check next week. Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted February 22 Author Share Posted February 22 Regarding the Software update - will do. Regarding the points you raise in item 2: 2. I've read (web posts) that the engine management system may have a default engine rev limit of 2500 RPM for the V6 TDI when stationary to prevent over revving? I Will never the less report this to Audi when I check the car in for the diagnostics check. 2a. Probably. I guess this is an original factory setting. 2b. Yes - steady at just under 1000 RPM 2c. No - steady on tick over. Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted February 22 Author Share Posted February 22 Regarding your Point 3 - no, not that I've noticed. A bit difficult keeping an eye intentionally on the Rev Counter whilst driving ;o} I too have wondered if the car is stalling at low speed. Bit unusual for a diesel automatic - but you never know? Would the RED Drive System Fault/Fail light come on if the engine stalls? Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted February 22 Author Share Posted February 22 Thanks Jason. If the car is indeed stalling does this point to a transmission or clutch issue? Hydraulics? Hopefully more will be revealed next week. Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted March 26 Author Share Posted March 26 OK - mystery solved !!! Initial diagnostics pointed to a faulty stop/start generator (AKA Alternator). A replacement was ordered and required shipping from Germany as none in the UK. The part was delivered and then an instruction received by my Audi garage NOT TO FIT THE PART and run another check - per Audi instructions. This new check indeed revealed the root cause of the problem that I have been experiencing. The problem was due to a defective Auxiliary Belt Tensioner. Required parts were fitted and included a replacement belt - this was more a precaution than requirement as the defective belt tensioner may have contributed to premature excessive wear. I insisted that the car was taken for an extensive test drive before taking it back. All was well - and still is. I now have the car back (after 2-3 weeks off the road while awaiting parts). Will monitor the situation, but reasonably confident that this time Audi have got it right. 1 Quote Link to comment Share on other sites More sharing options...
Hallam109 Posted March 29 Share Posted March 29 I have the same problem which Audi garage did you take it to and what was the cost Quote Link to comment Share on other sites More sharing options...
MikeSwidz Posted March 29 Author Share Posted March 29 My local Audi is in Worthing (Roundstone). Tell your Audi Service Dept that Audi have issued a bulletin (March 2024) regarding this fault and that it has nothing to do with the stop/start generator. If they find nothing then ask them to get in touch with Audi Worthing for details. The cost of the repair (parts/labour/VAT) was around £200. Hope this is the "fix" for your fault. 1 Quote Link to comment Share on other sites More sharing options...
Magnet Posted March 29 Share Posted March 29 Many thanks for the very useful update Mike. Kind regards, Gareth. . Quote Link to comment Share on other sites More sharing options...
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