Subaru Outback: P0453 Fuel Tank Pressure Sensor/Switch To High

Subaru Outback's EVAP system uses evaporative emissions control to move fuel vapors from fuel tank and fuel filler neck to fuel the engine.  If the pressure in the fuel tank becomes too high, P0453The engine light will turn on after the key is thrown.

Your Outback will not fail if the trouble code is P0453.  The EVAP is responsible for transferring fuel vapor.  It doesn't matter if it does that, or not. This has no impact on how your engine works.  This code is not to be ignored.

The EVAP system does not work all the time.  It uses a  valve to open and close the system to release fuel vapor into the engine to be burned off.

It is the fuel tank pressure sensor that detects excessive pressure.  This sensor measures air pressure within the tank. It does not measure fuel pressure.  When it does, the P0453 signal is sent.  The fuel tank pressure sensor can be found on top of the fuel tank, fuel pump or fuel level sending device.

The opposite of this code is P0452, which is thrown whenever the system pressure is too low.

P0453 Symptoms:  Subaru Outback

This code is usually not associated with any symptoms.  The check engine light will illuminate (that’s why you’re here).

You may only notice the fuel smell.  If your EVAP system doesn't properly remove fuel vapor it will seek other escape routes.

The causes

These are some of the most common reasons for P0453.

• Charcoal canister Vent valve, clogged
• Pressure sensor in fuel tank damaged (sensor or wiring).
• Tank with contaminated fuel
• PCM/ECM (highly unlikely)

Diagnostics for P0453 on the Subaru Outback

Diagnosing P0453 in your Outback can be challenging if you don’t have a scan tool that is capable of reading the fuel pressure sensor data or capable of commanding the vent valve to open and close.

How to Make Your Home a Better Place

• If you happen to notice the sound of air escaping when you take your Outback’s gas cap off, that is a telltale sign that the vent valve is bad, or the charcoal canister is bad(it’s pressure leaving the gas tank).  You can open the gas valve by driving for awhile.  It’s hard to notice the sound when you’re at a noisy gas station.
• Examine the wiring connecting to the fuel pressure sensor. If it is damaged or frayed, you should inspect it.  If it isn’t then the only way to really diagnose it is with a professional mechanic’s scanner.  This is difficult because you may need to remove the tank from your vehicle to be able to examine it.

What a Mechanical Engineer Will Do

• The data of the fuel pressure sensor will be captured by a mechanic to determine whether it detects any vacuum.
• The vent valve will be opened and closed by them.  You can also hear the engine running depending on your vehicle's year.

The fuel tank pressure data may be out of specification. A mechanic will check the wiring to the fuel sensor.  A mechanic will inspect the wiring leading to the fuel pressure sensor and replace it if that is found.

The charcoal canister must be replaced if the vent valve turns on and the pressure sensor works fine.  If the vent valve doesn’t come on, it will need replacement in order to clear P0453.

If it looks good, the PCM could have a problem.

Subaru Outback P0453 Conclusion

That’s pretty much it.  While there are only a couple of common things that’ll cause P0453, there it can be tough to diagnose it without the right equipment.  It’s not going to leave you stranded on the side of the road either.  It's possible to fix your Outback.