Subaru Outback P0451: EVAP Pressure Sensor → Range/Performance

Similar to all OBD-II codes P0451 The same meaning applies to all vehicles.  The following means: Subaru Outback‘s EVAP system has a pressure sensor that is malfunctioning in some way. 

The most common causes of P0451 are a bad EVAP Pressure Sensor, a clogged Fuel Tank Relief Val, EVAP Lines, EVAP Wiring, or a bad Fuel Cap.  Other causes can also be involved.  We’ll cover those directly below.

P0451 is usually caused by either a bad EVAP pressure sensor, a clogged fuel tank relief valve, EVAP lines, EVAP wiring, or a bad fuel cap….

Outback P0451 Symptoms

P0451 is not likely to affect how your Outback drives or runs.  Fuel mileage It is possible that some people may feel a bit of pain, although it's not likely to be severe. Service engine light will soon be on You will get one.  It is possible to also feel the slight Smells like gas. 

Concentrate on any other trouble codes that are EVAP-related and try to resolve them.

Subaru Outback - P0451 Causes

These are the top causes of P0451 generally.

Bad/Missing Fuel Cap

To diagnose P0451, the easiest way to begin is by looking at your fuel cap.  Since a missing, bad, or under-tightened fuel cap can make your Outback throw this code it’s a great place to start.

If you’ve gotten a “tighten fuel cap” message recently, but the cap was already tight, that’s a strong indication that there could be something wrong with the fuel cap.

A rubber seal is placed around fuel caps to prevent them from coming into contact with the fuel tank receiver.  You should ensure that the seal isn't dry-rotted or broken.  It should be replaced if it becomes damaged. New gas cap This could be the solution you are looking for to your problem.  However, fuel caps are often mistakenly attributed to the cause of P0451.

EVAP Lines and Wiring

You should next check your EVAP system lines or hoses for P0451 problems in Outback.  You should pay attention to where they are connected to other things, near exhausts, and touch any object that might slowly cut through them. 

The same principle would apply to checking the wiring harness.  The first thing you would do is check for damage.  You should pay particular attention where the plug connects to the EVAP pressure sensor.  The harness may need to be replaced if it is damaged or loose.

Also, the carbon canister may be harmful.

Low EVAP Pressure Sensor

This is a good time to inspect the fuel pressure sensor.  You’ll need a good scanner.  You’ll want to test to see if it is within the specs that Subaru requires before getting a new one.  Here’s a fantastic video on how to do just that:

Check your Fuel Tank Pressure Relief Valve

After everything is in order, I'd recommend a smoke test to check the fuel tank pressure relief valve.  These are often difficult to reach.  Here’s a link to a great video on how to Find the source of the leak if you don’t have a smoke machine.

Conclusion: Subaru Outback, P0451

Finding P0451 is not always easy.  The good news is that if that’s the only code that your Outback has, it shouldn’t really be a breakdown risk.

You can leave any comments or suggestions below.  We wish you all the best!