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DTC codes / P01xx · Fuel and air metering / P01A1

P01A1Alternative Fuel Tank A Pressure Sensor Circuit High

P01A1 indicates that the powertrain control module (PCM) has detected a voltage signal from the alternative fuel tank A pressure sensor that is higher than the expected range for the current operating conditions. This typically means the sensor circuit is open, shorted to voltage, or the sensor itself has failed, causing the PCM to see an abnormally high pressure reading.

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 no symptoms besides the warning light, especially if the fault is intermittent
  • Erratic or inaccurate fuel gauge readings if the pressure sensor shares data with the fuel level system
  • Reduced engine performance or stalling if the PCM limits alternative fuel operation to protect the system
  • Difficulty starting or switching to alternative fuel mode
  • Possible fuel smell or pressure-related noises from the tank area in severe cases

Common causes, most likely first

  1. Open circuit in the sensor signal wire (broken wire, corroded connector, or loose terminal)
  2. Short to voltage on the sensor signal circuit (chafed wire contacting a power source)
  3. Faulty alternative fuel tank pressure sensor
  4. Poor electrical connection at the sensor or PCM connector
  5. Failed PCM driver or internal circuit (rare but possible)
  6. Contamination or damage to the sensor due to fuel quality or debris
  7. Water intrusion into the connector causing corrosion and high resistance

How to diagnose and fix it

  1. Use a scan tool to verify the code and check live data for the tank pressure sensor voltage; compare to specifications
  2. Visually inspect the sensor and its wiring harness for damage, corrosion, or loose connections; repair as needed
  3. Disconnect the sensor and measure resistance or voltage on the signal circuit to check for opens or shorts; refer to factory wiring diagrams
  4. Check for reference voltage and ground at the sensor connector with the key on; repair wiring if voltages are incorrect
  5. If wiring and connections are good, test the sensor with a multimeter or replace it with a known-good unit and recheck
  6. Clear the code and perform a road test to confirm the repair; monitor live data to ensure the signal returns to normal range
  7. If the code persists after sensor replacement, diagnose the PCM and its connections, including checking for software updates or internal faults

Before replacing the tank pressure sensor

  • A high voltage code often results from an open circuit rather than a failed sensor, so always check wiring continuity before condemning the sensor.
  • Corroded or loose connectors at the sensor are a frequent cause, especially in vehicles exposed to road salt or moisture.
  • The PCM may set this code if the sensor signal circuit is shorted to voltage, which can happen if the harness rubs against a power wire.
  • On some vehicles, the alternative fuel tank pressure sensor is part of a larger assembly, and replacing just the sensor may not be possible.
  • Intermittent faults can be caused by vibration or temperature changes, so wiggle-test the harness while monitoring live data to catch intermittent opens.

Can I keep driving with P01A1?

If the vehicle runs normally, you can drive it to a repair shop, but avoid aggressive driving or towing until the fault is repaired. If the vehicle exhibits drivability issues or fuel smell, stop driving and have it towed to prevent safety hazards.

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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