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2001 subaru outback check engine light

My 2001 outback(AT, 98k, 2.5) has an issue with the check engine light coming on any time the weather is below 40ish (in AK that is plenty). The code that it give me is p1400(low pressure in evap system= gas cap off ) I have checked the gas cap plenty of times and it is definitely screwed on tight, I have replaced the gas cap. yet this light stays on. I am currently failing emissions testing and need to figure out what to fix or what to replace. I have contemplated adding a one tire stem to the old gas cap(wasn’t missing any O-rings) and slightly pressurizing my gas tank for the test(2-3 PSI).

Besides a loose gas cap, that code can also be triggered by a defective solenoid valve in the evaporative emissions system. In fact, that was one of the only two repairs ever needed on my '02 Outback. Luckily for me, the solenoid valve failed while the car was under warranty. However, this should not be an expensive repair for you, as the solenoid is easy to access.

went to the independant subaru repair place here in town and he said it is either the part or one of the wires on the way to it, wires first, then part. where is the device actually located?

It’s been quite a few years, but my recollection is that it was located next to the filler neck, and could be accessed fairly easily when the car is on a lift.

I don’t know how subarus work, but that problem in one car turned out to be a bad pump that pressurized the fuel system for a leak test.

Checking the meaning of the code P1400 it shows this, “Fuel Tank Pressure Control Solenoid Circuit Low Input”. So the trouble isn’t a pressure issue but an electrical issue as the shop you went to indicated (Specialized Import by chance?). Hopefully this is just a bad connection issue at the solenoid. My service data shows the solenoid is at the rear of the tank, about in the middle, and near the top possibly. Just as VDCdriver stated.

I’d have to drop the tank to get to it so I get to pay for the mechanics boat this month. between $100 and $300. The guy was actually honest though and said well it will cost extra depending on which step we fix it at. the shops sign says AK independent Subaru, we got enough up here that a mechanic can just work on them I guess. Thanks for the direction guys, I’ll try and post an update next week when it has been worked on.

Are you sure that there isn’t an access panel underneath the rear seat?
It would certainly be worth your time and effort to lift the seat, remove the sound-deadening mat, and look for an access panel.

Whether there is an access panel or not, I really doubt that the tank has to be dropped, simply because the dealership got me back on the road in less than 45 minutes when they replaced the solenoid valve on my essentially identical '02 Outback. Is your mechanic really familiar with Subarus?

Replaced the valve, same code, went to the shop, they checked the valve (it works great,as it should beings the dealer had to special order from subaru HQ, you can atually hear it manualy cycle if you listen really close), they checked the wires going to the computer they are carrying the correct amount of voltage, they loaded the wires and they still are carrying the correct amount of voltage(ampage?), they swapped the computer with another 2001 outback and had the code pop up again, they got another known good computer and tried a second computer same problem. I am required to spend 450 chasing this problem before I can get a pass on the emissions test. What the heck is this problem???

Are you sure they are working on the right one? Have you tried to see what happens if you remove the solenoid? It would be interesting to see if the code changes.

no, not actually sure, I’m not allowed in the shop while they are working. it is apparently right above the rear differential?? Currently I’m hoping that an unmanned dynamite truck happens to run into it while I’m at work tomorrow. I got an appointment with the dealer(who has problems diagnosing a bad alternator…) on Thursday ill keep an update.

The factory service data has a good service repair procedure for code P1400 so it shouldn’t be much of a problem to fix this. It is a pretty simple circuit.

The Main Relay supplies 12 volt power to one of the solenoid wires. The other wire ties to the ECU on pin a1. There are a couple of connectors between the ECU and the solenoid where a possible bad connection may be.