What it means
The pressure signal of alternative fuel tank C does not match plausibility checks against tank temperature and fill level. Sensor drift.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
The AFCM compares alternative fuel tank C pressure with expected values based on tank temperature and fill level. This code sets when the sensor signal remains electrically readable but falls outside those plausibility checks, which can happen if the sensor has drifted or shifted at its mount.
Common causes
Most likely first.
- Sensor zero drifted
- Sensor mounting loose - bias offset
- Sensor element aged beyond calibration window
Symptoms
- Check-engine light
- Alternative-fuel warning light
- Inaccurate tank pressure or fuel-level indication
How to diagnose it
- Save freeze-frame data and compare tank C pressure with fuel level and temperature in live data to identify the mismatch.
- With the vehicle in the conditions specified by its service information, check whether the pressure reading changes plausibly as tank conditions change.
- Inspect the tank C sensor mount for looseness or displacement that could bias its reading.
- Check the connector and wiring for damage or poor contacts that could distort the pressure signal.
- If the mount and circuit are sound, test the sensor against the manufacturer's specification and replace it if it has drifted.
Common fixes
- Secure the tank C pressure sensor correctly if its mounting is loose.
- Clean or repair poor connections in the tank C sensor circuit.
- Replace the tank C pressure sensor if its reading remains outside the specified plausibility range.
Can I keep driving?
Driving may be possible if there are no other symptoms, but tank C pressure, fuel level, or remaining range may be inaccurate and alternative-fuel operation may be restricted. Do not rely on the displayed range when planning a trip.
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.