Audi Q7 No-Start: Terminal 15 Circuit Investigation

Having dealt with a similar starting issue on my 2014 Audi Q5, I can share my experience as someone with some mechanical knowledge. When my car wouldn't start, the starter solenoid was engaging and the engine would crank, but it wouldnt fire up. After checking the basic stuff like battery terminals and fuses, it turned out to be a faulty connection in the ignition switch wiring. The workshop found that one of the main circuit breaks was due to a corroded connector in the ignition wiring harness. The repair involved replacing the damaged section and reconnecting everything properly. Total cost was 95 Euro including diagnostics and labor. Before suggesting specific solutions for your Q7, it would help to know: Are there any other warning lights on the dashboard? Does this happen consistently or intermittently? Have you noticed any electrical issues before the car won't start situation? What's the exact error code you're getting? This could help pinpoint whether you're dealing with a similar ignition switch issue or something else in the starting circuit.

Thanks for sharing your expertise. My Audi Q7 has 154991 KM on the clock and I replaced a few fuses already but still get the same error code. I noticed a voltage drop when testing with a multimeter at several points in the circuit. The power supply to the ignition module seems inconsistent. I also observed that all dashboard lights work normally until I try to start the engine. A few weeks back the car had some minor electrical glitches but they seemed to resolve on their own. The fuse box was checked during my last service 3 months ago and everything was marked as OK. Would it make sense to get the entire ignition wiring harness checked? Or should I focus on testing individual components first?

Thanks for the additional details about your Q7. The voltage drop you measured is a crucial clue pointing toward a potential wiring harness issue. On my Q5, before the complete failure, I also noticed similar voltage fluctuations, particularly around the ignition switch area. The inconsistent power supply to the ignition module combined with your previous electrical glitches suggests a failing connection somewhere in the circuit. The starter solenoid should receive a steady voltage when engaging, and any fluctuation can prevent proper engine start. From my experience, I would recommend: 1. Test the voltage at the ignition switch while someone turns the key 2. Check continuity through the main wiring harness sections 3. Inspect all ground connections near the starter circuit 4. Verify the starter solenoid operation with a direct voltage test Getting the entire wiring harness checked makes sense since intermittent electrical issues often indicate broader connection problems. The repair might cost between 150-400 Euro depending on what needs replacement. Quick tip: Pay special attention to any corroded or loose battery terminal connections, as these can cause similar symptoms even when they look fine externally.

Thanks everyone for the insights. After reading about your Q5 issues, I'm convinced my Audi needs a thorough electrical inspection. The voltage drop symptoms match exactly what I'm experiencing, and those intermittent electrical glitches now make more sense as warning signs. I'll focus first on testing the ignition switch and starter solenoid connections as suggested. A complete wiring harness inspection seems worth the investment, considering the car's mileage and the consistent voltage issues I measured. The fuse box will need another check too, even though it was serviced recently. Even if the repair ends up costing 400 Euro, it beats being stranded with a car that won't start. Will schedule an appointment with my mechanic tomorrow and have them specifically look at the electrical connections around the ignition circuit. Hoping it's just a matter of fixing some corroded wires rather than replacing the entire system. I'll update once I get the diagnostic results. The voltage testing points you shared will help me discuss the issue more effectively with the mechanic.