Sensor Reference Voltage "A" Circuit Low
The 5 V reference voltage on the A circuit (used by multiple sensors) is below threshold — short to ground or excessive current draw by a single sensor pulling the rail down.
Affected components
- Sensor reference circuit
- Ecu
Common causes
- High likelihood: Sensor or harness shorted to ground
- Low likelihood: ECU reference output damaged
- Low likelihood: Connector pins corroded - high contact resistance
Possible symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- Reduced-power or limp mode may occur
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.