Open circuit in the sensor signal or ground wire, or a damaged connector; Faulty alternative fuel rail temperature sensor; Corroded, loose or contaminated sensor connector pins; Signal wire shorted to a voltage supply; Poor sensor ground or reference supply fault; Fault inside the engine control unit or the alternative fuel control unit; Incorrect or faulty aftermarket conversion wiring or sensor installation.

P01B7

Alternative Fuel Rail Temperature Sensor Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
B7: FaultThe specific fault in that area

What it means

P01B7 means the engine control unit has seen the signal from the alternative fuel rail temperature sensor sit higher than its expected voltage range. This sensor is fitted to the secondary fuel system on bi-fuel or dual-fuel vehicles, such as gas or flex-fuel setups. A high reading usually points to an open circuit, a short to voltage or a failed sensor. Exact sensor location and wiring depend on the model and fuel system.

Symptoms

Engine warning light on
Poor or rough running on the alternative fuel
Hard starting or long cranking on the alternative fuel
Car switching back to petrol or the main fuel unexpectedly
Reduced power or poor fuel economy

Possible causes

Open circuit in the sensor signal or ground wire, or a damaged connectorlikely
Faulty alternative fuel rail temperature sensorlikely
Corroded, loose or contaminated sensor connector pinspossible
Signal wire shorted to a voltage supplypossible
Poor sensor ground or reference supply faultpossible
Fault inside the engine control unit or the alternative fuel control unitrare
Incorrect or faulty aftermarket conversion wiring or sensor installationrare

How to diagnose

Read all stored and pending codes and record the freeze frame data, noting which fuel was in use when the code set.
Check for related codes on the alternative fuel system, sensor supply or ground circuits, and look up any manufacturer or conversion-specific guidance for the model.
Inspect the sensor, its wiring and connector for damage, chafing, heat damage, corrosion or water ingress, especially if the system is an aftermarket conversion.
With a scan tool, view the live fuel rail temperature value. A very low or implausible reading, or one that does not change as the engine warms, suggests an open circuit or a sensor fault.
With the ignition off and the connector unplugged, check the sensor resistance against the specification for that model and compare it with the ambient temperature.
Check the signal wire for continuity to the control unit and for any short to voltage. Also check the ground circuit and the reference voltage at the connector.
Wiggle-test the harness and connector with the engine running or in live data to find intermittent faults.
If the wiring and sensor are good, check the control unit connector and power supplies before suspecting the control unit.

How to fix

Repair or replace damaged wiring and renew faulty connector terminals.
Clean and secure corroded or loose connector pins, and fix any source of water ingress.
Replace the alternative fuel rail temperature sensor if its resistance or live readings are out of specification.
Repair any short to voltage or faulty ground or reference circuit found during testing.
Replace or reprogram the relevant control unit only after the wiring and sensor are proven good, following the manufacturer or conversion supplier's procedure.

Can I keep driving?

Medium severity

The car can usually be driven short-term, often on petrol or the main fuel, but the alternative fuel system may be limited or unavailable. Get it checked soon, as poor fuel control could affect running and emissions.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.