What it means
Voltage on the pressure sensor signal line of alternative fuel tank C is below the expected window. Wire shorted to ground or sensor short.
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 monitors the signal voltage from the pressure sensor on alternative fuel tank C. This code sets when that signal is below the expected range, pointing to a signal short to ground, a shorted sensor, or a poor connector contact.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Check-engine light
- Alternative-fuel warning light
- Inaccurate tank pressure or fuel-level indication
How to diagnose it
- Check freeze-frame and live data to confirm that tank C pressure is stuck low or implausible when the code sets.
- Inspect the tank C pressure-sensor connector and signal-wire routing for corrosion, pin damage, or a wire rubbed through to ground.
- Using the manufacturer's wiring information, check the sensor's reference supply and ground before assessing the low signal.
- Test the signal circuit for a short to ground and check its continuity between the tank C sensor and AFCM.
- If the wiring and connector pass, test the tank C pressure sensor to the manufacturer's specification for an internal short.
Common fixes
- Clean corroded pins and secure the tank C pressure-sensor connector.
- Repair the signal wire where it is shorted to ground or damaged.
- Replace the tank C pressure sensor if it fails the manufacturer's circuit test.
Can I keep driving?
A shorted-low reading can make tank C pressure and fuel indications unreliable and may limit alternative-fuel operation. Drive only if the vehicle operates normally, avoid relying on its range display, and stop if drivability or fuel-system warnings worsen.
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.