VW Lupo Transmission Sensor Causes No-Start Issue

Had similar symptoms on my 2003 VW Polo with the automatic transmission at 82000km. The shift lock system was preventing engine start due to a faulty transmission control unit. The gear shifter would not properly register the park position, causing safety systems to prevent startup. Main symptoms matched yours: Unable to start, Check engine light, Rough shifting before complete failure, Transmission position sensor errors The transmission repair involved replacing the defective control unit and recalibrating the gear shifter position sensors. This was a serious electrical issue affecting the transmission management system, but not a mechanical transmission failure. The neutral position and park brake mechanisms also needed adjustment during the repair. Parts typically involved: Transmission control module, Shift lock solenoid, Position sensor assembly, Associated wiring harness While this requires specialized diagnostic equipment, its significantly less costly than a full transmission replacement. Would strongly suggest having a transmission specialist examine it rather than a general mechanic given the specific nature of these electrical/sensor issues.

Thanks for your detailed reply. Really sounds like the exact same issue I am dealing with. The gear linkage symptoms match perfectly, especially the problems with the shift lock system. Did they need to replace your entire transmission control unit or just repair the wiring? Also wondering about the total repair cost in your case and if you had any other transmission issues since getting it fixed? Looking to get a rough estimate before taking it to a specialist. Currently checking local transmission repair shops that focus on European cars.

Just wanted to update on the repair outcome. The automatic transmission problems were completely resolved after replacing the faulty control unit. Like your case, the shift lock system was not recognizing the gear shifter position correctly. The repair cost came to 1000€ for the new control unit, programming, and labor. The transmission specialist confirmed the gear linkage and mechanical components were actually in good condition, it was purely an electrical/control issue. Have put about 15000km on the car since the repair with zero transmission issues. The gear shifter now smoothly engages all positions and the neutral position safety interlock works perfectly. Starting reliability is back to 100%. Based on your identical symptoms, sounds like you are dealing with the same control unit problem. The investment was worth it since it avoided a much costlier full transmission replacement.

Thanks for the helpful advice. Just got back from the transmission specialist. Great news, it was indeed the control unit causing the transmission issues, just as suggested here. The repair bill came to 950€ total including parts and labor. The specialist found the original control unit had water damage which caused the gear linkage malfunction. They installed a new unit, recalibrated all the sensors, and cleaned up some corroded wiring while they were at it. Car starts perfectly now and the automatic transmission shifts smoothly again. The parking lock engages properly and that annoying check engine light is finally off. Really glad I asked here first, saved me from potentially getting overcharged for an unnecessary transmission replacement. Will update in a few months on how its holding up, but so far the transmission repair seems to have fixed all the issues. Thanks again for steering me in the right direction with the control unit diagnosis.