190ecosworth

Hi everyone, New to the forum but I really need your help. I’m completely stuck on a Skoda Superb II 2.0 TDI (170Hk) DSG6 (manual ignition key, NO electronic steering lock/ELV) and I’m officially out of ideas. I really hope someone here can point me in the right direction. The Backstory: The car died while driving due to a failed alternator (battery drained completely). The car was driven home, parked, and the battery was disconnected. While replacing the alternator, a faulty xenon ballast was also replaced. A brand-new battery was installed. Upon reconnecting the battery terminals (there was a normal minor spark), the car's ignition went completely dead. Current Symptoms: No Terminal 15: Turning the key does absolutely nothing. The instrument cluster (dashboard) is 100% pitch black—not even the center MFD screen turns on or gives any warnings. Working Comfort Electrics: Central locking, interior lights, hazard lights, radio, and parking lights work perfectly. Manual Jumpering: If I manually jumper the Terminal 15 relay under the steering wheel (bridging pins 30 and 87), power is successfully sent to the cabin fuse box (verified 12V at dashboard fuse SC6, and steering column fuses SC2 and SC16). However, the cluster still remains completely black. Diagnostic Data (OBDeleven): When the Terminal 15 relay is manually jumpered, I can establish VCDS/OBDeleven communication with the car. BCM / Central Electrics Live Data: BCM successfully registers the physical key positions! Terminal 15 (input) and Terminal 50 (input) switch from OFF to ON when I turn the key. The Conflict: However, another live data channel shows Terminal 15 (via LIN) / Steering column switch information as "Not Installed". Fault Codes: The system is flooded with permanent communication codes that cannot be cleared: Terminal 15 implausible signal No signal/communication / Lost connection to: Instrument Cluster (J285) and Steering Column Module (J527). Network Status: Modules like the ECU, TCU, ABS, Gateway, and BCM are fully awake and communicating with the scanner, but they ALL complain about missing communication from specifically the Cluster and the Steering Column Module. What has been verified and tested so far: Fuses & Relays: Every single fuse (engine bay E-box, cabin fuse box, and the large SA-metal strip fuses in front of the engine e-box) has been continuity tested and confirmed OK and power-supplied. All "Relay 100" relays have been bench-tested and function perfectly. No pins in the relay carriers are backed out or damaged. Ignition Switch & Lock: The mechanical lock and the electrical ignition switch (D-switch) behind it have been tested and are fully operational. Steering Column Module (J527): The module's internal circuit board has been inspected and measured—it appears to be fully functional. (Note: The indicator stalk had some intermittent glitches months prior to this event, and the car occasionally threw a steering angle sensor G85 code before, but worked fine). Wiring & Grounding: Tested with a jumper cable directly from battery negative to the engine block with no change. The wiring harness near the engine/DPF/ABS is verified intact and has not been pinched or damaged during the alternator swap. B+ on the new alternator is connected correctly to the designated M8 post. LIN-bus: The LIN-bus wire from the alternator regulator is verified not shorted. The Dilemma: Since the BCM sees the key turning "ON" in live data, the hardware signal gets into the car. But the BCM refuses to ground the Terminal 15 relay automatically. Even when I bypass the relay manually, the Cluster and J527 refuse to boot up on the CAN-bus network, leaving them completely dead to the rest of the car. It feels like a digital lockout or a specific power line (Terminal 30/constant power) to just these two modules has died, but all fuses are intact. Has anyone encountered the BCM or Gateway completely dropping/disabling the LIN-bus to the steering column after a battery reconnect? Could a voltage spike during battery connection have locked the BCM logic, or am I missing a hidden fuse/fusible link somewhere? Any input or crazy ideas are highly appreciated. I am completely out of options! Thanks in advance.

I just did the same work for the second time, But did not bolt off the ac compressor and did not take off the bumpers. I just raised the engine and took the radiator fan off. Same engine. 2h in total.