Fuel and air

P01B2 — Alternative Fuel Tank 'A' Level Sensor Circuit High

Severity: low Safe to drive

What P01B2 means

The control module monitors the signal voltage from the fuel level sensor in the alternative fuel tank, such as a gas cylinder or a second fuel tank. P01B2 sets when that voltage is above the expected range. Typical causes are an open signal circuit, a short to power, or a failed sensor.

Symptoms

  • Check Engine light on
  • Alternative fuel gauge reads wrong (pegged or dead)
  • P01B2 stored in ECU memory
  • Inaccurate fuel remaining or range estimates
  • Possible odd or early switching between fuels

Possible causes

  1. Failed alternative fuel tank level sensor
  2. Open signal circuit or poor connector contact
  3. Corroded or damaged wiring, or signal wire shorted to power
  4. Missing or poor sensor ground
  5. Sensor power supply fault
  6. Rarely, a fault in the ECM or the gas system control module

How to diagnose

  1. Read codes and freeze frame data, clear the code and see if it returns
  2. Compare the scan tool fuel level value with the actual amount of fuel
  3. Inspect the sensor connector and harness for corrosion, chafing and moisture
  4. Measure reference voltage and ground at the sensor connector using the factory wiring diagram
  5. Test the signal wire for an open circuit or a short to power
  6. Check sensor resistance across the float's range and compare with specification
  7. If wiring is good, replace the sensor and retest

Common fixes

  • Replace the fuel level sensor in the tank
  • Repair or replace damaged wiring and connectors
  • Restore the sensor's power and ground supply
  • Update software or replace the module only after ruling out everything else

Questions and answers

Can I drive with a P01B2 code?

Usually yes. The engine runs normally, but the alternative fuel gauge may be wrong. Track your mileage and refueling so you don't run out of fuel.

What most often causes P01B2?

Most often it's a bad level sensor or a wiring problem such as an open signal wire, poor contact or a corroded connector. Start with a visual check of the connector and voltage measurements.

How do I clear P01B2?

Fix the cause first, then clear the code with a scan tool. If the fault is still present, the code will come back after a few drive cycles.

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.