Audi Q5 Diesel Glow Control Unit Causing Multiple Issues

Had the same problem with a 2011 Audi A4 diesel engine. The symptoms match exactly, constant preheating lamp, check engine light, and exhaust smoke under acceleration. A diagnostic test revealed faulty connections in the glow plug control module. The issue turned out more complex than initially thought. The heating element in one glow plug had failed completely, causing engine misfire and vehicle stalling issues. The wiring harness connecting to the control unit was also corroded, creating intermittent electrical problems. The repair required: Replacing all glow plugs as a set, Installing new control module, Rewiring the connector assembly, Clearing fault codes This was a serious repair requiring specialized diagnostic equipment. The vehicle needed to stay at the shop for 2 days due to the complex nature of accessing the components. After the fix, the diesel engine performance returned to normal with no more warning lights or smoking issues. Worth getting it checked soon as continued driving can cause further damage to the injection system and potentially lead to complete engine failure.

Thanks for sharing your experience. I had similar issues with my Q5 recently. My engine light would come on during cold starts and the engine misfire was quite noticeable, especially in the morning. The glow plug system needed a complete overhaul. The symptoms seem identical to what you experienced. Did you remember how much the total repair ended up costing? Also curious if any other issues came up since getting it fixed? Asking because after my repair I noticed the vehicle stalling occasionally, which turned out to be an unrelated fuel system problem.

Thanks for asking about the follow-up costs. After seeing the mechanic, the glow control unit defective issue was much simpler than in your case. The diagnostic showed just a loose cable connection to the control unit causing the problems. The repair only needed a cable fix and proper reconnection, costing 95 Euro for parts and labor. No complete system overhaul was necessary in my case. Since fixing the faulty connection, the diesel engine has run perfectly with no engine misfire or vehicle stalling issues. The warning lights disappeared completely and cold starts work normally again. The quick fix saved me from more extensive damage to the injection system that could have developed if left unattended. Unlike your situation, I haven't experienced any additional fuel system problems or other car maintenance issues since the repair. This really shows how similar symptoms can have different root causes in diesel engines, ranging from simple connection problems to more complex system failures that require complete overhauls.

After dealing with all these issues, I finally got everything sorted out with my Q5. Took it to a different mechanic this time who actually found multiple problems with the glow plug system. The glow control unit was completely shot and two of the glow plugs were burned out. The total repair came to 780 Euro, including: New glow control unit, Complete set of glow plugs, Labor costs, Diagnostic testing The diesel engine runs perfectly now, no more smoke, warning lights, or cold start problems. The mechanic also checked the fuel system while fixing the glow plug issues, which prevented potential problems down the line. The repair took about 6 hours but was worth every cent. Really glad I didnt wait longer as the mechanic mentioned the failing glow plugs were starting to affect other engine components. Much better experience than my previous repair attempts. Best decision was switching to a shop specializing in diesel engines rather than a general repair place. Should have done this from the start and saved myself some headaches with the initial misdiagnosis.