@RallyFOZ perhaps this will help, but if you have the repair manual, I suspect you already have this?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

Thanks, but I have the complete repair manual. It doesn't show or explain where the part is located.

The drawing in EC-02303 looks like it's next to a dipstick, but when I check above & under the engine, there's nothing that looks like that part.

The drawing doesn't give enough clarity to figure out it's location.

Does anyone have a photo of it on the vehicle?
🤔

 

I did more research and discovered that on some cars, the 'fuel tank pressure sensor' is located on, or next to, the fuel filler/ neck/ pipe/ hose, behind the wheel-well splash shield.

Does that makes sense on a Subaru?
Does anyone have a photo of where it's located?
🧐

 

UPDATE:
I took the rear passenger wheel-well fender liner out. The part is nowhere to be seen. W.T.F. Subaru?!
😡
Does anyone have a photo of where the "Fuel tank pressure sensor" is located?
📸
Please help... I'm going crazy trying to find it.
🤪
Thanks!

 

Thanks, but I have the complete repair manual. It doesn't show or explain where the part is located.

@RallyFOZ actually, the technical service diagrams tells you a lot, even the previous one I posted. Since you have the service manual, I'm not going to post what you already have. Take a look at: FUEL INJECTION FUEL SYSTEMS FUH4DOTC ► General Description ► FUEL INJECTION (FUEL SYSTEMS) ► 5. FUEL LINE

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

@RallyFOZ actually, the technical service diagrams tells you a lot, even the previous one I posted. Since you have the service manual, I'm not going to post what you already have. Take a look at: FUEL INJECTION FUEL SYSTEMS FUH4DOTC ► General Description ► FUEL INJECTION (FUEL SYSTEMS) ► 5. FUEL LINE

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

Thanks for your reply Bobby!

I tried to follow the path you listed, but my service manual is 4364 pages, so I'm not sure if I got the right page. Is this what you're referring to? (see pic)
If so, it doesn't show if the part is on top of the fuel tank or exactly where...

Can you please clarify and/or post a picture?

Thanks for your help!

 

If you are in the back seat and facing the rear of the vehicle is your fuel pump towards the left side of the vehicle? It's possible the Fuel tank pressure sensor is nearly in the middle, ie almost inline with drive shaft hump, and there probably is not service panel under the rear seat for this.. Are you 100% sure it's not your fuel cap? Or something else, this fuel pressure sensor is rarely replaced, I don't recollect anyone in this community ever needing to replace this component and that is likely why no has said anything. The sensor maybe throwing up the P0451 because it is reading correctly and actually detecting something wrong. And you are going down the path that you think the sensor is broken and reading the wrong pressure.

This might help: 2012 Subaru Forester Fuel Tank - Subaru Parts Deal

 

Thanks for the reply!

Yes, the gas cap was the first thing I changed. See OP.

When I took the service panels off the fuel pump and sub level assembly under the rear seat, this is what I saw (see pics). I didn't see any extra electrical connectors, parts, or wires in-between the two service hatches. Sorry I couldn't get a good picture of the space in-between as it's too cramped for the camera.

When I took the wheel-well lining out I inspected the fuel filler pipes and everything looked good (see pic).

 

Anything near the rear edge of the fuel tank?

 

Not that I can see from underneath. The fuel tank is covered by splash shields, the drive-shaft, exhaust, suspension, and rear sub-assembly. If only the repair instructions were more specific as to its location.

I even called my local trustworthy mechanic and he looked up the repair in his All-Data system. His instructions and diagram matched mine, so he was too stumped.

 

It has to be under the vehicle the clue is "Lift up the vehicle".

@Sackett Steve can probably help us if he's around (thanks)

 

Agreed, as that's what the shop manual says... unless there was a typo or something got lost in the translation?

I have looked extensively underneath the car for the fuel tank pressure sensor, mounting bracket, and wires, but can't find it anywhere, which is why I looked under the rear seat fuel pump service hatches, and under the wheel-well splash shield.

If I only had a photograph of what part of the car it's next to for reference.

I'm going cuckoo for Cocoa Puffs trying to figure this out.
🤪

Thanks for the tip I'll PM Steve!

Just for grins I added a picture of the fuel tank pressure sensor, according to the Subaru parts site.

 

Thanks for the tip I'll PM Steve!

Not necessary & I'd rather you didn't as he would've been notified by the mention I gave.

 

Just to recap here's the full details on the trouble code...

P0451 SUBARU - Evaporative Emission Control System Pressure Sensor Range/Performance.

Possible Causes:
1. Faulty Evaporative Emission System (EVAP) Pressure Sensor.

2. Evaporative Emission System (EVAP) Pressure sensor harness is open or shorted.

3. Evaporative Emission System (EVAP) Pressure sensor circuit poor electrical connection.

4. Faulty Engine Control Module (ECM)

Behavior: The vehicle starts, runs, and drives fine, but the gas mileage is about 2 to 3 MPG lower.

I can clear the check engine light with my always plugged in UltraGauge, but it comes back on after 3 drive cycles.

 

Apologies for the duplicate post and for contacting Steve. I didn't realize it happened automatically.

 

I understand this must be frustrating but as there's been 207 views of this thread to date I think you should let it settle now until someone has a definitive answer

 

Understood, thanks man.

Got to get it fixed so it will pass inspection in September, so I've got some time.
😅

 

I have the Haynes manual Foresters 2009-2016. It informs the reader that there is a fuel-tank-pressure-sensor installed. From the installation instructions I can only assume its on top of the fuel tank. The manual does not indicate where it is.

 

The shop manual pic from above shows it in the vicinity of the right-rear corner of the tank. The parts diagram also shows the same general location (A). You mention there's a lot of stuff blocking the view. If you're set on DIYing this, maybe your next step is to remove easily removed parts to get a better view. If it entailed dropping the subframe or exhaust, the manual would say that, right?

I've resorted to using my phone's camera to get a view of spots I cannot see directly. Maybe that's an option for you to try.

 

Thanks for your replies! I found a video on YouTube showing a 2010 Forester fuel tank removal, and captured some pics. The video is at:

The image shows the Fuel tank pressure sensor on a bracket bolted to the fuel tank, next to the fuel filler hose.
(see pic)

I looked under my 2012 Forester again, but could not find anything in the same location. However I did find 2 empty bolt holes.
(see pic)
I also could not find the smaller vent hoses that are supposed to be next to the fuel filler hose.

Did Subaru change the fuel tank design and not update the repair manual?!
😵

Frustrated, I called it a night and watched "SoftRoadingTheWest" a Subaru Forester channel on YouTube. By chance he was talking about hooking up fog lights and how he doesn't tap into the fuse box for power, but connects directly to the battery, to avoid affecting the Subaru's sensitive electronics.

Then I had an idea...💡

I also have aftermarket fog lights that were wired up when I got the car, by using a fuse tap off the 12 volt outlet/cigarette lighter.

When I checked the fuse box under the dash, the 20 amp fuse was burnt out and the fuse tap had slight carbon scoring from being loose.
So, I removed the fuse tap and replaced the fuse.

I later watched another video about the P0451 code and they said to check for EVAP leaks.
So, I checked my oil catch can and hoses, and decided to remove it to eliminate any potential vacuum leaks from the PCV.

I then cleared the check engine code and took the car on 4 short trips, shutting it off and removing the keys each time, to complete the required drive cycles for the CEL reset. The car ran normally and the CEL did not come back on!
I've been driving it for over a week and no check engine light!
😊

LESSON LEARNED:
Don't use a fuse tap for fog lights. Wire high amperage lights directly to the battery with an appropriate relay and inline fuse.

When I have the time I will pressure test the oil catch can. If it's okay I will hook it back up to the PCV hose.

Thanks a lot for your help guys, I really appreciate it!

But, the mystery still remains...
Where is the Fuel tank pressure sensor?!
🤔

 

So, it's exactly where the earlier diagrams indicated

But, the mystery still remains...Where is the Fuel tank pressure sensor?!

I think you mean where is YOUR fuel tank pressure sensor.

 

@RallyFOZ curious... you didn't find the fuel tank pressure sensor, but you fixed the problem?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

 

@RallyFOZ curious... you didn't find the fuel tank pressure sensor, but you fixed the problem?

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]

Yes. I've been driving it for almost a week now and the check engine light has not come back on.

Still can't find the darn sensor though.
I'm beginning to wonder if it's in the gas tank?

 

UPDATE: After many months of CoronaVirus lockdown and working from home, the car has not been driven much. After sitting for almost 3 weeks, I started it up to drive it... and the stupid check engine light came back on with the same code P0451. ARRRG!!
😵
Any advice would be greatly appreciated.

 

THE REAL FIX...

After a lot of trouble shooting and talking to multiple mechanics, I finally figured it out.

The problem (P0451 code) was caused by a defective: Vapor Canister Purge Solenoid (Part # 16131AA070) OEM $47.

The major problem was finding it, as the parts location was mislabeled in the Subaru and Haynes repair manuals, as well as the Subaru parts database, showing the purge solenoid's location near the gas tank at the back of the car. You would think this is correct because that's where the EVAP pump and charcoal canister are, hidden under the cargo area floor.

The purge solenoid is ACTUALLY located in the engine compartment, on the driver's side, to the right of the throttle body, in-between the air intake hose and the intake manifold, bolted underneath it.
Because of all the stuff in the way, the part is very hard to see.

Once I found the purge solenoid, the repair was quite simple: disconnect the battery ground, remove the air intake hose, un-bolt the purge solenoid, unplug the electrical connector, disconnect two small hoses, then replace the solenoid, and reconnect/reinstall everything in reverse order.

After clearing the trouble codes I followed the steps in the Subaru manual and drove the car for about 15 minutes at highway speeds, to get the EVAP system to fully reset and get to a "ready" state.
Everything is working great now, the car runs better, and it passed New York State inspection.
Woo Hoo! 😁

Thanks to everyone for their patience and help! 👍

Here's a picture of the purge control solenoid location...