Audi Q7 Diesel Glow Plug System Causing Smoke And CEL

Had similar issues with my Audi A6 2015 diesel. The constant preheating lamp and engine preheat malfunction pointed to a wiring problem in the ignition system. The smoke during acceleration was concerning, but the root cause turned out to be a defective part in the preheating control module. The repair involved testing the vehicle heater connections and replacing corroded plug connectors. While diagnosing, the technician found that moisture had damaged the wiring harness connecting to the preheating unit. This is actually a common issue that can occur even with regular maintenance. Not a major mechanical problem, but it requires proper diagnostic equipment to pinpoint the exact connection fault. The repair took about 4 hours to complete, including testing all control module functions. Most important was verifying that all preheating cycles worked correctly after the fix. Worth noting that ignoring these symptoms can lead to starting problems and potential engine damage, especially in cold weather. The complete diagnostic check is essential as similar symptoms can also indicate glow plug issues.

Thanks for sharing your experience with the preheating unit problem. I went through almost exactly the same with my Q7 last winter. Really helps to know the car electronics diagnosis pointed to similar wiring issues. Since having it fixed the preheating lamp has stayed off and no more smoke issues during acceleration. Quick follow up, can you remember roughly what the total repair cost was? Also curious if youve had any other ignition system problems pop up since getting the defective part replaced?

Thanks for asking about the costs. After getting the electrical fault fixed at the shop, I havent seen any ignition system problems return. The repair focused on the preheating control unit which was showing defective signals. The total came to 95 Euro for fixing the faulty cable connections. The car electronics diagnosis confirmed it was just the wiring connection causing the issue, not the entire control unit itself which would have been much more expensive. The engine preheat system has worked flawlessly since the repair. No more warning lights or smoke problems during acceleration. Good preventive maintenance of the ignition system helps avoid these issues from recurring. Regular checks of the control unit connections are worth doing, especially before winter weather hits.

Had my Q7 checked at a repair shop last week. The mechanic found similar wiring issues with the preheating unit. They did a complete car electronics diagnostic and spotted corrosion in the connectors, just like your case. Total bill came to 120 Euro for fixing the electrical fault and cleaning the connections. The vehicle heater now works perfectly, no more warning lights or smoke issues. The engine preheat cycle runs smoothly, especially during cold starts. Honestly relieved it wasnt a major problem like I first feared. The mechanic suggested I get the connections checked yearly before winter to prevent future issues. Makes sense given how a simple wiring problem can trigger so many warning signals. Glad I got it sorted before any serious damage occurred.