VW Polo Diesel Glow Plug Control Unit Failure Signs

Had the same electrical fault symptoms on my VW Golf TDI 2011. The engine preheat system showed identical warning signs, constant glow plug indicator and check engine light, plus black exhaust smoke during acceleration. The diagnosis revealed a defective part in the preheater control module, specifically corroded cable connections at the glow plug harness. The car preheater system requires proper voltage distribution to all glow plugs. When connections deteriorate, it affects the entire ignition system performance. The repair involved replacing the complete glow plug control module and harness assembly, plus cleaning all connection points. Not a simple fix since accessing the components required partial removal of the intake manifold. The repair prevented potential long-term engine damage, as faulty preheating can lead to improper fuel combustion and injector issues. If experiencing these symptoms, recommend having a full electronic diagnostic scan done first. The fault codes will indicate if its specifically the preheat control unit or related components in the ignition system. Best to address this promptly to avoid more serious engine complications.

Thanks for sharing your experience. I had very similar symptoms on my Polo 1.6 TDI. The heating module was failing and the mechanic confirmed it with diagnostic tests. The engine preheat warning stayed lit even after warm-up, which was quite annoying. Just wondering, can you remember roughly how much the total repair cost you? In my case, replacing the defective part and labor came to around 380€, but prices can vary. Also, has everything been working properly since the fix or did you notice any other issues? Looking back, dealing with preheating unit problems early definitely saved me from bigger headaches down the road. Getting a proper diagnosis really makes a difference with electrical problems like these.

After getting the preheating control unit fixed at my local shop, everything has worked perfectly. The total repair was much cheaper in my case, just 95€ to repair a faulty cable connection in the preheating system. The mechanic found the electrical fault was due to a damaged plug rather than needing to replace the entire control unit like in your case. The engine preheat cycle now works as intended, with no more warning lights or smoke issues. What really helped was the thorough diagnostic scan they did first to pinpoint the exact problem in the vehicle heater system. Been driving for 6 months since the repair without any related problems. Good point about addressing these electrical issues early. A failing preheating unit can lead to much costlier engine repairs if left unchecked. Your repair cost seems reasonable given they had to replace the complete unit rather than just fix connections like in my case.

Had to share an update after getting everything sorted. Took the car to a different mechanic who specializes in car electronics and VW systems. Right away they did a proper diagnostic scan that confirmed the faulty preheating control unit. The repair process was smoother than expected. They replaced the entire preheater assembly and fixed some corroded wiring connections they found during inspection. Total cost came to 380€ which included parts and labor, seemed fair considering the thorough job they did. Really glad I switched mechanics. The new shop took time explaining the electrical fault they found and showed me the defective part they removed. Since the repair, the car starts perfectly even in cold weather, no more warning lights, and the black smoke issue is completely gone. Looking back, finding a mechanic who actually knows their way around modern car electronics made all the difference. Would definitely recommend getting a proper diagnosis done if anyone runs into similar preheating unit problems.