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DTC codes / P01xx · Fuel and air metering / P01B0

P01B0Alternative Fuel Tank A Level Sensor Range/Performance

P01B0 indicates that the powertrain control module (PCM) has detected an out-of-range or erratic signal from the fuel level sensor in the alternative fuel tank, often called Tank A. The PCM compares the sensor voltage against expected values for the fuel volume and flags the code when the reading stays outside the valid window or changes too abruptly for the conditions.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Fuel gauge reads empty or full regardless of actual alternative fuel level
  • Fuel gauge fluctuates or sweeps erratically while driving
  • Driver information center displays an incorrect distance-to-empty or fuel range
  • Illuminated check engine light or service vehicle soon message
  • Reduced engine performance or forced gasoline operation if the PCM cannot trust the alternative fuel level
  • Often no symptoms besides the warning light when the fault is intermittent

Common causes, most likely first

  1. Faulty fuel level sensor inside the alternative fuel tank
  2. Wiring harness damage, corrosion, or loose connector at the tank sensor
  3. Poor ground connection for the fuel level sensor circuit
  4. Contaminated or degraded alternative fuel affecting sensor float movement
  5. Sticking or mechanically binding sensor float arm
  6. PCM internal fault or outdated software misinterpreting the sensor signal
  7. Aftermarket or incorrect sensor installed previously

How to diagnose and fix it

  1. Connect a scan tool and record the fuel level sensor voltage and fuel level percentage with the key on and engine off, then compare to the actual tank level
  2. Inspect the sensor connector and harness at the alternative fuel tank for corrosion, chafing, or pushed-out pins
  3. Measure resistance or voltage at the sensor across its full travel and compare with the manufacturer's specification
  4. Verify the sensor ground circuit has less than 0.1 volt drop under load
  5. Check for technical service bulletins or PCM software updates that address false P01B0 setting
  6. Replace the fuel level sensor or sending unit if electrical and mechanical checks confirm it is out of specification
  7. Clear the code and perform a road test with the scan tool recording to confirm the repair

Why alternative fuel level sensors set P01B0

  • A common oversight is diagnosing the sensor when the real problem is a chafed harness near the tank mounting bracket, which only shows up when the suspension flexes.
  • The PCM may set P01B0 when the alternative fuel level signal is plausible but does not change over a long drive, so a sensor that is stuck rather than electrically failed will trigger the code.
  • Some vehicles use a second fuel level sensor for the gasoline tank, and swapping the two signals during diagnosis can lead to replacing the wrong component.
  • After refueling, the PCM expects a rapid voltage change; a slow-responding sensor can set P01B0 even though the gauge eventually reads correctly.
  • A weak battery or low charging voltage can cause the PCM to misread the sensor signal, so always verify system voltage before condemning the sensor.

Can I keep driving with P01B0?

The vehicle remains safe to drive because the fault affects fuel level reporting rather than the fuel delivery system itself. Avoid relying on the fuel gauge for refueling decisions and do not let the alternative fuel tank run low until the fault is repaired.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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