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Discussion Starter · #1 ·
Hey Folks,
I feel like I've tried everything on this one and still keep getting the p1440 code after the drive cycle.
I've:
-Replaced fuel cap
-Replaced Evap Vent Valve
-Replaced Evap Cannister
-Replaced Evap Selenoid
-Replaced Fuel filler neck

I've examined the connections below the rear seat and there are no broken or frayed wires.
What else do I need to check?
Help please!

-Nick
 

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Have you verified the valve control circuit electrically? It's one thing to look at the wires; another to put a meter on them and record readings.
 

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Discussion Starter · #3 ·
I haven't.
Where might I find a wiring diagram? I'll need to identify what wire to test.
What voltage should I be looking for with the key on?

Thanks
-Nick
 

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(formerly) 03 H6 OBW , (presently) 06 WRX Sportwagon & 2021 Honda CR-V
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raster ---would the green diag. connectors help him with this?
 

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brief search suggests to check all the evap hoses for blockage, pinching, holes, or cracks, or, purge valve may be stuck open.


any other codes occur with this?
 

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Discussion Starter · #6 ·
Thanks. I did check all the hoses and all seem to be in good shape. I put a few shots of compressed air through as well and none seem to be blocked. I put a new purge valve in as well, so that shouldn't be causing it either.

Nope, no other codes at all.

What are these green connectors you mentioned?

-Nick
 

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they cycle relays/solenoids and fans on/off for troubleshooting. small, green maybe taped to a harness near or underneath the steering column? not sure if they occure different places in different models. Don't leave them connected and drive.
 

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Discussion Starter · #8 ·
they cycle relays/solenoids and fans on/off for troubleshooting. small, green maybe taped to a harness near or underneath the steering column? not sure if they occure different places in different models. Don't leave them connected and drive.
Ah yes, I do have that green connector. I did cycle the solenoids in trying to determine if that was the issue, and I ended up replacing them with new ones anyway, so they should be operating correctly.
The code, I believe, means low voltage to the tank pressure, so somehow the correct voltage reading isn't getting back to the ecu.

I'm unsure what to try next (besides the voltage reading when I can figure out which wire to test).

Thanks
-Nick
 

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do you ever notice any 'whooshing' of air when you remove the gas cap?

is the car new to you? are you in the habit of 'topping off' the fuel tank when refueling? is any other driver doing that?

I'm also wondering if you could clear the code, then only loosely attach the gas cap (to reduce spillage) and drive the car some. You should get codes (p0440 - maybe others) but, if you DON"T get P1440 - it may mean there is an actual physical failure somewhere - not just an electrical problem.

ever see any signs of rodent damage around the car? any codes before this began?

in what part of the world are you located?
 

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Discussion Starter · #10 ·
Thanks man.
Yes, I get the "whooshing" of air when I remove the gas cap. And yes, the car is new to me. I know to not top the car off with gas, so I always stop at the first sign that the tank if full.
I haven't tried clearing the code and then driving with a loose gas cap to see what other codes might be thrown. I can give that a try and report back to see what happens to the p1440 code in this instance.

No other codes before this began, or at all, but it was like this when I bought the car, and I'm just trying to get her all straightened out. No signs of rodents or any rodent damage.
I'm located in Spokane, Washington.

Thanks again!
-Nick
 

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DTC P1440 — FUEL TANK PRESSURE CONTROL SYSTEM FUNCTION PROBLEM (LOW INPUT)

A "low input" fault usually means that where the ECM expects an electrical connection to have a high voltage (high in this case being battery voltage), the actual voltage is low, essentially missing. This is usually caused by an open circuit, or it could be a short to ground.

In the attached diagnostic, when the pressure control solenoid is not being activated, there should be battery voltage at ECM terminal #10. When the solenoid is turned on, the ECM essentially grounds pin #10, so that the voltage at the terminal will be low.

If there's an open circuit in the wiring from the battery, through the relay and solenoid and on to terminal #10, the ECM will not see the expected battery voltage, and the solenoid will not function.

If there's a short to ground in the wiring from the solenoid to ECM terminal #10, the ECM will again not see the expected battery voltage, and the solenoid would probably remain activated all the time.

The "green connector" test is mentioned in the diagnostics, and can be used to see if the pressure control solenoid is switching on and off.
 

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does it seem like there is a vacuum when you remove the cap?

anyway, seems like the report you are getting about tank pressure may be legit - that might point to a clog or insect nest inside some evap tubing or possibly a 'flooded' charcoal canister?

but, other issues with wiring might be in the mix and not allowing the evap system to function well enough to properly equalize the tank pressure?

does the car take fuel normally or does it click-off too easily? OH, how did the filler neck look?

nice - plainOM and rasterman have much more experience with this stuff than me. the evap system does some complex stuff to try to purge/allow air and fuel vapors to flow the 'correct' directions. any cracked plastic, bad hoses or broken wires are gonna cause problems.
 

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Discussion Starter · #14 ·
Yea, definitely vacuum when removing the gas cap. I switched the cap to verify it was good. I also switched the charcoal canister to rule that out as well.
It takes gas just like it should with no issues, and all lines seem to be in good shape. None are cracking, and there is no fuel smell or evidence of any leaks anywhere. The filler neck was in good shape too, as I'm not in an area that has much moisture, so rust is at a minimum.

Thanks for the help and tips. I'm still at a loss except for verifying voltage.
-Nick
 

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dsure seems like a purge or 'drain' valve clog or operation problem to me.

one of the hoses from the charcoal can goes to the 'drain' valve - maybe run with the hose off for a while, see if the code comes back?
 

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was the filler neck new Subaru part?
 
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