What it means
Voltage on the alternative fuel temperature sensor signal line is above the expected window. Wire shorted to B+ or sensor open.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The AFCM monitors the signal voltage from the alternative fuel temperature sensor. This code sets when the signal rises above its expected range, which can point to a signal wire shorted to battery voltage, an open sensor, or a poor connector contact.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open temperature sensor
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine or alternative-fuel system warning light
- Alternative-fuel operation may be limited
- Reduced fuel economy
How to diagnose it
- Review freeze-frame and live data to see whether alternative-fuel temperature is fixed high or otherwise implausible.
- Inspect the temperature-sensor connector and harness for corrosion, loose pins, and contact with power wiring.
- Use the manufacturer's wiring information to check sensor power and ground and identify the temperature signal wire.
- Test the signal circuit for a short to battery voltage and check continuity between the sensor and AFCM.
- If the wiring is intact, test the temperature sensor for an open condition using the manufacturer's procedure.
Common fixes
- Reconnect or clean the temperature-sensor connector and repair damaged pins.
- Repair a signal wire shorted to battery voltage or an open in the circuit.
- Replace the temperature sensor if it is open or fails the specified test.
Can I keep driving?
The AFCM may limit alternative-fuel operation when it cannot trust the temperature input, and fuel economy may worsen. Drive only if the vehicle operates normally and heed any fuel-system warnings.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.