VW Golf TDI Glow Plug Issues Cause Smoke & Warnings

Had almost the exact same issue with my 2013 VW Jetta TDI. I have some experience working on diesel engines, but this particular problem required professional diagnosis. The symptoms matched yours precisely, persistent glow plug indicator light, check engine light, and smoke under load. After the engine misfire became more frequent, I took it to a workshop for a proper diagnostic test. The technician found that the glow plug control unit had a faulty connection, specifically a damaged wire harness to one of the heating elements. The whole repair, including parts and labor, cost 95€. They had to replace the damaged wiring and check all glow plug connections. What started as an occasional glitch turned into a real performance issue. Getting it fixed promptly prevented potential damage to other components. Before offering more specific advice, could you share: Have you noticed any starting problems, especially in cold weather? Are there any other warning lights active? Has the fuel consumption increased? Did these symptoms appear gradually or suddenly? Understanding these details would help determine if your issue is similar to what I experienced with the control unit wiring.

Last service was at 85000km and everything was fine back then. After reading this reply, I checked the cold start behavior more carefully, engine cranks longer than usual before starting, especially in the morning. The smoke is light gray and only visible during hard acceleration. No other warning lights besides the ones mentioned. Fuel consumption seems normal. The symptoms started about 2 weeks ago, first with just the glow plug indicator, then the engine light came on a few days later. The symptoms match exactly what you described with the faulty control unit. Based on the similar experience shared, I will have the glow plug system checked professionally. It sounds like delaying the repair could lead to more serious engine problems.

Thanks for those additional details about the cold start behavior, that extended cranking time is really telling. My repair experience with the similar issue on my Jetta TDI matches your situation exactly, right down to the progression of symptoms. The light gray smoke during acceleration combined with the cold start issues strongly suggests a glow plug system problem affecting fuel combustion. When my control unit failed, the diesel engine also struggled with proper combustion, leading to those exact symptoms. After my repair, the cold start performance improved dramatically. The engine would fire up instantly, even in cold weather, and the smoke issue disappeared completely. The fix also prevented what could have developed into more serious engine misfire problems. Since your vehicle maintenance was up to date and the symptoms developed gradually just like mine did, it really points to the glow control unit being the culprit rather than a maintenance-related issue. One thing I learned from my experience, while the repair itself isnt extremely expensive, letting it go too long can cause carbon buildup and potentially damage other components. Getting it diagnosed soon would be the smart move, especially given how closely your symptoms match what happened with my car. Would recommend documenting when exactly the symptoms occur (like during cold starts or acceleration) to help the technician diagnose it more efficiently.

Based on the similar experience you shared and my latest observations, I will definitely schedule a diagnostic test this week. The cold start issues and smoke patterns you described match my situation perfectly. Since these symptoms appeared gradually over the past 2 weeks, starting with the glow plug indicator and progressing to include the check engine light, I want to address this before it causes more serious problems. Your experience with the faulty control unit wiring and its repair cost gives me a clear picture of what to expect. The car maintenance history shows everything was fine at the last service, so this sudden change in heating element performance points strongly to an electrical issue rather than general wear. I will document the cold start behavior and smoke patterns during acceleration as suggested, this should help speed up the diagnostic process. Given how a failing glow plug system can impact the diesel engine performance and potentially cause additional damage, getting this fixed promptly seems like the best course of action. Thanks for sharing your repair experience. It helped confirm my initial suspicion about the glow plug control module and convinced me to take action sooner rather than later.