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DTC codes / P01xx · Fuel and air metering / P01A0

P01A0Alternative Fuel Tank A Pressure Sensor Circuit Low

P01A0 indicates that the powertrain control module (PCM) has detected a low voltage signal from the pressure sensor circuit of the alternative fuel tank designated as Tank A. The PCM expects the sensor to report a voltage within a calibrated range that corresponds to the tank's pressure, and a sustained low reading tells the module that the circuit is shorted to ground, the sensor has failed, or the reference voltage is missing.

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

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) on the dashboard, often with no other noticeable symptoms.
  • The alternative fuel system may default to gasoline operation or refuse to switch over to the alternative fuel.
  • Rough running or stalling if the vehicle attempts to run on the alternative fuel with incorrect pressure readings.
  • A fuel gauge or pressure gauge that reads abnormally low or fluctuates erratically.
  • Reduced fuel economy or performance because the PCM limits alternative fuel usage to protect the system.

Common causes, most likely first

  1. A faulty alternative fuel tank pressure sensor that internally shorts to ground and pulls the signal voltage low.
  2. Damaged or chafed wiring in the sensor circuit, particularly where the harness rubs against the tank or chassis, causing a short to ground.
  3. Corroded or loose electrical connectors at the sensor or PCM, introducing resistance that drags the signal voltage down.
  4. A missing or low 5-volt reference voltage from the PCM to the sensor, often due to a shorted sensor or wiring on that reference circuit.
  5. A failed PCM driver or internal circuit for the pressure sensor, though this is less common than sensor or wiring faults.
  6. Moisture intrusion into the sensor connector or sensor body, creating a conductive path to ground.

How to diagnose and fix it

  1. Connect a scan tool and record the freeze-frame data and live pressure sensor voltage to confirm the signal is stuck low under the conditions that set the code.
  2. Visually inspect the sensor, its connector, and the wiring harness for chafing, corrosion, or loose pins, repairing any obvious damage before replacing parts.
  3. Disconnect the sensor and measure the 5-volt reference voltage at the connector with the key on; if it is missing, trace the reference circuit back to the PCM.
  4. With the sensor disconnected, check the signal wire for continuity to ground; a short to ground indicates a wiring fault that must be repaired.
  5. If the reference voltage is present and the signal wire is not shorted, substitute a known-good sensor and clear the code to see if it returns.
  6. Perform a voltage drop test on the sensor ground circuit to rule out a poor ground that could skew the signal low.
  7. After repairs, clear the diagnostic trouble codes (DTCs), verify the sensor voltage reads within specification, and complete a drive cycle to confirm the code does not reset.

What a low pressure signal really means

  • A low signal voltage does not automatically condemn the sensor; a shorted 5-volt reference circuit inside another sensor on the same shared reference can pull the entire reference low and set this code.
  • The alternative fuel tank pressure sensor often shares its reference and ground with other sensors, so a fault in a seemingly unrelated component can cause P01A0 to appear.
  • Technicians who replace the sensor without checking the reference voltage at the connector frequently find the code returns because the real fault is a rubbed-through wire behind the tank.
  • On some vehicles, the PCM sets P01A0 only after a calibrated soak period, so the code may not reappear immediately after a repair and a full drive cycle with a cold soak is required to validate the fix.
  • A pressure sensor that reads low can cause the PCM to command the alternative fuel system off, leading to a gasoline-only default that the driver may misinterpret as a separate fuel system failure.

Can I keep driving with P01A0?

The vehicle is generally safe to drive because the PCM will default to gasoline operation when the alternative fuel pressure signal is implausible, but you should avoid extended driving on the alternative fuel system until the fault is repaired. Have the circuit diagnosed promptly to prevent potential fuel system damage or a no-start condition if the vehicle relies solely on the alternative fuel.

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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