ECM/PCM Power Input Signal Low
The ECM/PCM switched-battery input reads below threshold while the ignition is on. Either the main relay does not close, the supply wire is broken or shorted to ground, or the battery is too low. Engine usually fails to start until the input recovers.
Affected components
- Main relay
- Power input wire
- Battery
Common causes
- High likelihood: Main relay does not pull in
- Medium likelihood: Open supply wire
- Medium likelihood: Severely discharged battery
Diagnostic notes
- The malfunction indicator lamp may illuminate
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.