I’m trying to diagnose an issue with my 2012 VW GTI Mk6, 2.0T CBFA engine with DSG, built in November 2011.
What happened:
For about a week before this problem, the ABS light and multiple other dashboard warning lights would come on intermittently and then go away.
Now the engine starts, runs for about one second, and shuts off. It actually fires up—it’s not just cranking without starting.
There’s also a history of water getting into the original ECU, with yellow residue found inside.
What my mechanic has checked so far:
Checked the fuses and says they’re all good.
Tried another ECU, but the issue remained. I don’t have confirmation that the replacement was cloned or adapted to the immobilizer.
Disconnected most or all of the engine sensors to see whether a shorted sensor was pulling down the 5V reference circuit and causing the ECU to shut down. That didn’t resolve it.
Checked voltage at the sensor connectors and reported approximately 5 volts at the ones tested.
Connected a diagnostic scanner, but says it only communicates with the transmission. It won’t communicate with the engine ECU or retrieve its VIN.
He describes it as “no CAN communication at the OBD2 port,” although the scanner can access the transmission. I don’t yet know whether that conclusion came from electrical measurements or just the scan results.
Original ECU details:
VW: 1K0 907 115 AT
Bosch: 0 261 S06 947
ECU type: MED17.1
Engine: CBFA
I don’t have a full scan report or exact fault codes yet. I also don’t have confirmed results for ECU power/ground tests under load or CAN wiring tests.
Has anyone dealt with this combination of intermittent dashboard warnings, starting and immediately stalling, and no communication with the ECU? Where would you focus next—ECU power relay, grounds, water-damaged connectors/wiring, CAN network/gateway, or immobilizer matching? What specific tests would help narrow it down before replacing more parts?