FTPSensor

Fuel Tank Pressure Sensor (FTP)

Group: Emissions and exhaust

The FTP sensor measures the pressure or vacuum inside the fuel tank. The computer uses it to detect leaks in the EVAP vapor system, the source of the well-known P0442, P0455 and P0456 codes.

Contents

What does the FTP sensor do?

During the EVAP test, the computer closes the vent valve and opens the purge valve to pull vacuum on the tank, or pressurizes it with a pump on some vehicles. Then it seals everything and uses the FTP to watch whether the vacuum holds. If it is lost too quickly there is a leak: large (P0455), small (P0442) or very small (P0456).

Where is it located?

On top of the fuel tank (in the fuel pump module) or next to the charcoal canister.

Signal type and reference values

  • 3 wires: 5 V, ground and signal.
  • With the gas cap off (atmospheric pressure): about 2.5 V on many sensors.
  • Vacuum makes the voltage drop; pressure makes it rise.
  • The differences measured are very small, in the range of inches of water or a few kilopascals.

Values are a guide only: always check the manufacturer's data for your engine.

Symptoms of a bad FTP sensor

  • Usually no driveability symptoms.
  • Check engine light on.
  • Trouble refueling (the pump nozzle keeps clicking off) if there are other EVAP faults.
  • Gasoline smell if there is a real leak.
  • Codes P0450 to P0454 for the sensor itself, or P0442, P0455 and P0456 for leaks.

How to test the FTP sensor step by step

  1. Start with the simplest thing: tighten or replace the gas cap.
  2. With the cap removed, the FTP should read atmospheric pressure (close to 0).
  3. Check 5 V and ground at the connector; many FTP sensors share the 5 V reference with other sensors.
  4. Use the scan tool to run the EVAP test or command the valves, and watch whether the FTP reading changes.
  5. To find the leak itself, the most effective tool is a smoke test.

Trouble codes related to the FTP sensor

Frequently asked questions about the FTP sensor

Can a loose gas cap turn the light on?
Yes. It is the cheapest cause of P0455 and P0457. Tighten it until it clicks, clear the code and see whether it comes back.
Can I keep driving with an EVAP code?
Yes, it does not affect how the engine runs. But it may make you fail the emissions inspection and, if you smell gasoline, it should be checked soon.

Updated September 25, 2026. Values are a guide only: always confirm them in the service manual for your engine.

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