SPN 629 is a diagnostic trouble code for Controller #1 Bad Intelligent. Usually a voltage anomaly.
FMI 12 – Device Or Component
FMI 8 – ECM error, engine off timer fault
ECM calibration and connections, fuses
FMI 2 – Data Erratic, Intermittent, or Incorrect
This FMI indicates that the data from the control module is inconsistent, intermittent, or incorrect. Check the connections between the ECM and other control modules, as well as the wiring harnesses and power supply. Look for loose connections, corrosion, or damaged wires.
FMI 3 – Voltage Above Normal or Shorted to High Source
This FMI suggests that the control module is experiencing a high voltage issue or a short circuit. Inspect the wiring and connections for any signs of damage or a short circuit. If the wiring and connections appear to be in good condition, the control module itself may be faulty and need to be replaced.
FMI 4 – Voltage Below Normal or Shorted to Low Source
This FMI indicates that the control module is experiencing a low voltage issue or a short circuit to ground. Check the wiring and connections for any signs of damage or a short circuit. If the wiring and connections are in good condition, the control module may be faulty and need to be replaced.
FMI 12 – Bad Intelligent Device or Component
This FMI suggests that there is an issue with the control module itself, such as a faulty microprocessor or internal component. The control module may need to be replaced or reprogrammed.