P1668

DTC P1668
Anti-Theft Alarm serial link fault Drive cycle A:Signal out of range - above maximum.

Possible causes by suggested order of priority:
- Open circuit - C637/33 (LGS) to C661/10 (LGS).
- Connectors C661, ECM C637 (B).
- Alarm ECU Faulty.
- Alarm ECU not fitted.

Open circuit - C637/33 (LGS) to C661/10 (LGS).
- Check resistance > 1M Ohm

Connectors C661, ECM C637 (B).
- Check for connector not correctly latched, backed out pins, damaged pins, corroded pins

Alarm ECU Faulty.
CHECK THE FOLLOWING:
- Carry out BCU diagnostics.
POSSIBLE FAULTS
- Problem with alarm ECU (BCU).

Alarm ECU not fitted.
CHECK THE FOLLOWING:
- Verify that the vehicle is intended to have an alarm. If so check that market programming options are correct and that the correct ECUs are present.
- If the vehicle is not intended to have robust security re-program the Motronic ECM for non-robust security.
POSSIBLE FAULTS
- Problem with vehicle configuration.
- Problem with ECM security set-up.