Fuel and air

P01AD — Alternative Fuel Tank Temperature Sensor Circuit High

Severity: medium Safe to drive

What P01AD means

The engine control unit detected too high a voltage in the temperature sensor circuit of the alternative fuel tank, such as a CNG or LPG tank. The sensor signal normally changes with fuel temperature, and the ECU uses it to work out fuel density and delivery. A high reading usually points to an open circuit, a poor connection or a failed sensor.

Symptoms

  • Check Engine light on
  • Reduced fuel economy
  • Rough running or hesitation
  • Possible switch to gasoline or limited alternative fuel operation
  • Odd temperature or fuel level readings from the fuel system

Possible causes

  1. Failed alternative fuel tank temperature sensor
  2. Open signal wire or poor connector contact
  3. Signal wire shorted to power
  4. Corroded, damaged or wet connector terminals
  5. Open sensor ground circuit
  6. Rarely, an ECU fault or software error

How to diagnose

  1. Read all codes and freeze frame data and look for other alternative fuel system codes
  2. Inspect the sensor connector and harness for damage, moisture and corrosion
  3. Check the tank temperature reading on a scan tool and compare it with the actual temperature
  4. Unplug the sensor: a reading that changes suggests a short to power, one that stays high suggests an open circuit
  5. Measure reference voltage and ground at the connector with a multimeter
  6. Test the signal wire for opens and shorts to power
  7. Check the sensor resistance against the spec for your vehicle
  8. If wiring and sensor are good, check the ECU and for software updates

Common fixes

  • Replace the alternative fuel tank temperature sensor
  • Repair the wire or replace the damaged harness section
  • Clean or replace the connector and terminals
  • Update or reflash the ECU, or replace it if confirmed faulty

Questions and answers

What does code P01AD mean?

The ECU is receiving too high a voltage from the alternative fuel tank temperature sensor circuit. It's usually caused by an open circuit, a poor connection or a bad sensor.

Can I drive with P01AD?

Usually yes, but alternative fuel metering may be less accurate and fuel use may rise. Have it diagnosed soon.

How do I clear P01AD?

Fix the cause first by checking the sensor and wiring. Then clear the code with a scan tool. If the fault is still there, the code will return.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.