ECM/PCM Power Input Signal Range/Performance
The switched-battery input to the ECM/PCM is present, but the level or transient behaviour is out of plausibility — sagging during cranking, slow ramp-up after main-relay close, or noisy. Often caused by aged main relay contacts or a weak battery feed under load.
Affected components
- Main relay
- Power distribution
- Battery cables
Common causes
- High likelihood: Aged main relay contacts with rising contact resistance
- Medium likelihood: Weak battery sagging during crank
- Low likelihood: Sensor element aged beyond calibration window
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.