Fuel Supply Heater Control Circuit High
Voltage on the fuel supply heater control line is above the expected window. The sensor heater warms the element to operating temperature (~600 °C); without it the lambda sensor stays inactive in closed loop and the ECM cannot trim mixture.
Affected components
- Fuel supply heater
- Wiring harness
Common causes
- High likelihood: Control wire shorted to B+
- Medium likelihood: Open relay coil
- Low likelihood: Connector pins corroded - high contact resistance
Diagnostic notes
- The malfunction indicator lamp may illuminate
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.