Audi TT Terminal 15 Starting Issue, Expert Help Needed

I experienced a very similar issue with my 2017 Audi TTS. With some experience working on ignition systems, I can share what helped resolve this problem. The symptoms matched exactly, no starter engagement and error codes related to the ignition circuit. After initial troubleshooting, it turned out the ignition switch wasnt sending proper signals through the circuit. The voltage drop testing showed inconsistent power supply to the starter solenoid. The root cause was a loose connection in the wiring harness leading to the ignition switch. The workshop found damaged insulation had caused intermittent circuit breaks. Total repair cost was 95 Euro, mainly for diagnostic time and repairing the connection. Before workshop visits, you might want to check: Voltage at the starter solenoid while attempting to start, All fuses related to the ignition circuit, Power supply connections at the ignition switch itself To provide more specific guidance, could you share: Current battery voltage reading, Exact error codes showing up, Whether dash lights illuminate normally, If this happens consistently or intermittently This info would help determine if youre dealing with the same connection issue or potentially something else in the ignition system.

Last serviced at 86593KM, but after inspecting the voltage drop patterns more closely on my starter solenoid, I suspect a deeper issue. Using a multimeter, I found unstable readings from the ignition switch to the main fuse box. The circuit break seems intermittent, which explains why sometimes the dash lights flicker before failing completely. The battery voltage stays steady at 12.6V, but there are significant drops when attempting ignition. The wiring harness visual inspection revealed no obvious damage, though the connection points near the starter look slightly corroded. Thanks for the detailed breakdown of your repair, it gives me a clearer direction for further investigation. All error codes point to terminal 15 circuit issues: P0615 P0914 P1511 Will focus on testing the connections around the ignition switch before booking a workshop appointment.

Thanks for providing those voltage readings and error codes, they actually mirror what I experienced before discovering my wiring harness issue. The steady 12.6V battery reading with drops during ignition attempts matches the symptoms I encountered. Those error codes definitely confirm the Terminal 15 circuit problems we discussed. In my case, the P0615 was the key indicator that led to finding the faulty connection. The corrosion you mentioned near the starter is concerning, this could create additional voltage drop issues beyond the initial circuit break problem. After fixing my TTS, I learned that the power supply path through the ignition switch is particularly sensitive to connection quality. The workshop found that even slight corrosion in the fuse box area can cascade into these intermittent circuit issues. A thorough cleaning of the battery terminals might help, but based on your voltage readings, I suspect youll need similar harness repair work to what fixed my car. The flickering dash lights particularly match my experience, it was the first sign something was wrong with the voltage distribution through the system. Would recommend getting the workshop to specifically check the harness connection points near both the ignition switch and fuse box. That resolved the terminal 15 issues completely in my case.

Thanks for the insight about the harness connection points. After spending more time with the multimeter, I can confirm the voltage drop patterns match what you described. The dash lights continue to flicker, and Ive noticed the battery terminal connection, while clean, shows some resistance variation during testing. Current readings show: Battery steady at 12.6V, Voltage drops to 8.2V during start attempts, Circuit break seems to occur mainly when the key is in start position The error codes (P0615, P0914, P1511) persist, but your experience with the wiring harness repair gives me hope its a relatively straightforward fix. Going to schedule a workshop visit focusing specifically on the ignition switch connections and harness inspection. Just to be thorough, I cleaned all accessible battery terminals and connection points, but the intermittent circuit issues remain. Based on your repair cost reference, this sounds more reasonable than my initial fear of needing a complete ignition system replacement. Will proceed with professional diagnosis targeting the areas you mentioned, particularly the harness connection points near the fuse box.