What it means
Alt fuel rail temp sensor signal voltage above expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The alternative fuel rail temperature sensor reports fuel temperature to the control module through an electrical signal. P01B7 sets when the signal voltage is above the expected range, which can happen when the signal circuit is open or connected unintentionally to battery voltage.
Common causes
Most likely first.
- Signal wire open
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light on
- Alternative-fuel rail temperature reading may be inaccurate or unavailable
- Poor running or reduced power may occur
How to diagnose it
- Save freeze-frame data and check whether rail temperature data is unusually high, fixed, or unavailable while the fault is active.
- Inspect the rail temperature sensor connector and harness for a disconnected or backed-out pin, corrosion, broken wires, or damaged insulation near a power source.
- Monitor rail temperature data while gently moving the accessible harness to see whether the reading changes with movement.
- Using the manufacturer's wiring information, check the sensor signal circuit for an open and for an unintended connection to battery voltage.
- If the wiring checks out, test the rail temperature sensor and its supply and ground against the manufacturer's specification.
Common fixes
- Reconnect or repair a loose rail temperature sensor connector and its pins.
- Repair an open signal wire or wiring that is shorted to a power source.
- Replace the rail temperature sensor if it fails the manufacturer's test.
Can I keep driving?
The alternative-fuel system may receive an unreliable rail temperature reading, and poor running or reduced power may occur. Avoid demanding driving if performance is affected and have the circuit checked promptly.
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.