S4 Glow Plug Warning Light Haunts Audi Owner

Had the same glow plug trouble on my 2016 Audi A6 TDI. The symptoms matched exactly, constant preheat light and error codes. Rough idle during cold starts was the biggest red flag, especially in cold weather. The diagnosis revealed two failed glow plugs causing incomplete engine combustion. This affected fuel efficiency and engine performance significantly. The repair involved replacing all glow plugs as a set, plus the glow plug control module which was also damaged. This is considered a serious repair since faulty glow plugs can lead to starting problems and potentially damage the engine if left unchecked. The diesel engine relies heavily on proper glow plug function for optimal combustion, particularly during cold starts. The repair resolved all issues, no more warning lights, smooth cold starts, and restored fuel efficiency. Would recommend getting it checked soon, as continuing to run with failed glow plugs risks further engine complications. Make sure to use OEM parts for the repair. Aftermarket glow plugs often dont last as long and can cause similar issues to resurface sooner.

Thanks for sharing your experience. Dealing with similar cold start and glow plug problems currently. Curious about the repair cost for the full set of plugs and control module? My engine misfire issues during cold starts are getting worse and the check engine light just came on too. The rough idle is especially noticeable in the morning. Good point about using OEM parts, planning to stick with those. Has everything stayed fixed since the repair or have you noticed any other issues popping up?

Thanks for asking about the repair costs. After seeing the mechanic last month, the total came to 440 Euro for fixing the defective glow plugs and related issues. This included replacing the full set of glow plugs using genuine OEM parts. Since the repair, the diesel engine starts perfectly even in cold conditions. The rough idle issue completely disappeared, and fuel efficiency returned to normal levels. Engine combustion is smooth now, especially during those critical morning cold starts. No additional problems have emerged since the fix. The check engine light hasnt returned, and the preheat indicator now functions normally. The investment in OEM parts was worth it for reliable engine performance and proper glow plug operation. If your symptoms are worsening, especially the engine misfire and rough idle, getting it repaired sooner rather than later will prevent potential damage to other engine components. The fact that your check engine light is now on suggests the problem might be escalating.

Thanks for the advice. Finally got the repair done last week and wanted to share my experience. The mechanic found 3 bad glow plugs causing the cold start problems. Total repair cost was 520 Euro including labor and OEM parts. They also discovered the glow plug control module had minor damage, but it was still functional so we left it for now. The engine misfire issues and rough idle are completely gone. Cold starts are smooth again and the check engine light cleared up right after the repair. Really glad I didnt wait longer, the mechanic mentioned the failing glow plugs were starting to affect other components. The diesel engine is running much better now and fuel consumption has improved too. Definitely worth fixing it properly with quality parts rather than trying cheaper alternatives. No more problems since the repair and the preheat indicator is working normally. Engine combustion is back to optimal and morning starts are no longer an issue.