What it means
The control module monitors the alternative fuel tank A level sensor circuit. It sets this code when it detects an electrical fault, such as a signal outside the expected circuit range.
At a glance
- Usually lights the check-engine light
How it works
The alternative-fuel tank A level sensor reports how much fuel is in that tank to the control module. P01AF sets when the module detects an electrical fault in tank A's level sensor circuit, so the displayed alternative-fuel level may be wrong or unavailable.
Common causes
Most likely first.
- Level sensor failure
- Open or short in sensor wiring
- Loose, damaged, or corroded connector
Symptoms
- Check-engine light on
- Alternative-fuel level reading may be inaccurate or unavailable
- Alternative-fuel system warning may appear
How to diagnose it
- Scan for freeze-frame data and compare the reported tank A level with the actual fuel level and any available alternative-fuel warning.
- Inspect the tank A level sensor connector and accessible wiring for looseness, corrosion, moisture, or damage.
- Check the sensor signal and associated circuit wiring for opens or shorts using the vehicle wiring diagram.
- Check connector terminal fit and circuit continuity, moving the harness gently to reveal an intermittent contact.
- Test the tank A level sensor against the manufacturer's specification if its wiring and connections are sound.
Common fixes
- Reconnect and secure the tank A level sensor connector.
- Clean corroded terminals and repair damaged wiring.
- Repair an open or short in the tank A level sensor circuit.
- Replace the tank A level sensor if it fails testing with a sound circuit.
Can I keep driving?
Do not rely on the displayed alternative-fuel level to judge how far you can travel; keep adequate fuel in tank A and refuel conservatively. If an alternative-fuel warning or abnormal running occurs, stop safely and have the system checked.
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.