P068A Error: Engine Won't Start (Relay J271) (Solution)

P068A is a common error code in modern VAG diesel vehicles, which often leads to the engine failing to start ("engine cranks but does not start"). The fault relates to the main relay for the engine control unit (J271), which is either not switching off correctly or has worn contacts.


What does P068A mean?
The engine control module (ECM) continues to receive voltage through the main relay (J271) even after the engine is turned off, and reports this as a fault. The relay "sticks" or fails to open properly. Conversely, a faulty relay can also prevent the control module from receiving the correct voltage during startup, which would cause the engine not to start.


Typical symptoms:
- Engine won't start (starter motor turns, but engine doesn't ignite).
- The engine only starts after multiple attempts.
- The battery is draining overnight (the control unit remains active).
- Engine check light is on.
- No communication with the engine control unit during diagnostics.
- Engine stalls while driving (rarely).


Most common causes:
- Faulty relay J271 (main motor control unit relay), contacts worn or stuck, defective solder joints internally.
- Corrosion on the relay carrier/fuse box in the engine compartment (due to water ingress).
- Fuses for the engine control unit are blown or broken.
- Corrosion on the motor control unit's ground connection.
- The control unit itself is defective (very rare).


Diagnosis with VCDS:
- Auto-scan: Error code P068A is present in the engine control unit, but often the control unit cannot be accessed (the engine control unit is without power!).
- Determine the location of relay J271 within the vehicle (location varies depending on the model).
- Remove the relay and test it with a multimeter (check switching behavior and contact resistance).
- Measure voltage at the motor control unit (ECU) pins with the ignition ON and OFF.
- Check the fuses in the engine compartment fuse box.