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Old 12-04-2001, 12:04 PM   #1
Buffalo Bob
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Question Locking Gas Cap = CEL?

About 3 months ago, my CEL came on. Since I hadn't had the O2 recall taken care of, I went back to the dealer. They pulled the code and informed me that it was due to my aftermarket (locking) gas cap, which I've had for a year and a half, and that they'd have to charge me next time.

Well, my CEL has come on 3 times since then, and I just keep reseting it (pulling fuse 5 is SO much easier than pulling the negative cable). Does anyone know what code shows up when the gas cap is loose, and are there any other causes for that code?
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Old 12-04-2001, 01:22 PM   #2
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I would bet that you gas cap is not sealing properly. The subaru gas tank is a sealed unit and the ECU actually throws a code when it senses a leak.

I dont know if there is a rubber gasket or anything on the locking cap, but maybe you need a new one.

Jeff
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Old 12-04-2001, 03:32 PM   #3
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FYI locking gas caps are CRAP!! they NEVER seal properly...replace that thing with a FACTORY gas cap ASAP!!. the seals ALWAYS crap out in the POS caps.

Jeremy
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Old 12-04-2001, 06:40 PM   #4
MrHorspwer
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Considering OBD-II codes should be the same across the board... P0400 is the code that will set when a fuel filler cap is not sealing, loose, or missing. When doing its EVAP tests, the ECU pulls the fuel tank into a vacume to check for leaks. Being the system is sealed, the tank should hold a specified amount of vacume. P0400 sets when a large leak is detected, usually the tank won't even pull a vacume. Aftermarket locking gas caps are prime suspect for setting this code. Try an easy comparison... put your stock cap back on and see if the code reoccures. Oh yeah, if you remove you filler cap while the test is running (refilling the tank with vehicle running), the code will possibly set.
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Old 12-04-2001, 07:39 PM   #5
Peaty
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I used a Stant locking gas cap on my RS from 3 cars ago I got in 91 I think. I've never had a problem with a CE lamp coming on from it. I took it off because I did this:

http://www.scoobymods.com/mods/impre...kinggascap.php
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Old 12-05-2001, 03:03 AM   #6
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Quote:
Originally posted by MrHorspwer
Considering OBD-II codes should be the same across the board... P0400 is the code that will set when a fuel filler cap is not sealing, loose, or missing. When doing its EVAP tests, the ECU pulls the fuel tank into a vacume to check for leaks. Being the system is sealed, the tank should hold a specified amount of vacume. P0400 sets when a large leak is detected, usually the tank won't even pull a vacume. Aftermarket locking gas caps are prime suspect for setting this code. Try an easy comparison... put your stock cap back on and see if the code reoccures. Oh yeah, if you remove you filler cap while the test is running (refilling the tank with vehicle running), the code will possibly set.
i would LOVE to see a car set that code...those codes are manufacturer specific...honda's get a P1456 for a loose gas cap...or a leak in the system...IIRC subaru's get a 1414...yes it's somwhere in the 400 nubmers but the 1 in front makes it a manufactuer specific code..

peaty-consider yourself lucky...my brother bought one to put on his car cause his fialed cause of the gas cap...took it there right after buying it and failed the pressure test....was told FLAT out that they suck and always fail on a STANT machine....the cap was made by stant.

Jeremy
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Old 12-05-2001, 11:35 AM   #7
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My bad... it is a GM DTC P0440 that sets when a gas cap is loose. I was under the impression that universal OBD-II codes... the ones that begine with P0, not P1... were the same across the board, no matter the manufacturer. Under that thinking, a leaking cap in a GM would set the same DTC as a leaking cap on a Toyota, or a Subaru, or a BMW. I guess I was mistaken. But hey, I do know if a GM gas cap is loose, it'll set a P0440
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Old 12-05-2001, 07:47 PM   #8
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No, the codes are not manufacturer specific, it is mandated by law what the definition for each code is. Due to the manufacturer's different approches to diagnosis of problems and incessant whining to the EPA, there are sometimes 2 or more codes that have almost the exact same meaning.

Good example, GM cars will almost always set a P0300 (cylinder misfire, not specific to any cylinder) when they misfire, regardless of which cylinder misfires.

Chrysler cars will set a P0301 (cylinder #1 misfire) or P0302, etc
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Old 12-06-2001, 12:14 AM   #9
LVSUBARU
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Mercedes is P0445 or P0442. I see it all the time. Buy a new cap!!
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Old 12-06-2001, 03:31 AM   #10
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yamaharocket- wait till you get a honda with a P1456...then you can say they are the same across the board.

oh and honda's tell you what cylinder they misfire on....P0301...po302...p0303...etc...

oh yeah....DTC P1456 on a civic tonight...once again aftermarket gas cap...but honda gas cap and FTP voltage drops back down like it should rather then staying high.

jeremy
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Old 12-06-2001, 09:38 PM   #11
LVSUBARU
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HndaTch627, I don't know about you, but when I get a car in under warrenty with a large evap leak DTC, it gets a canister shut off valve. That or a purge valve! Especially when it's slow!
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Old 12-06-2001, 11:51 PM   #12
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GMs also set cylinder specefic misfire DTCs.
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Old 12-07-2001, 02:45 AM   #13
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Quote:
Originally posted by LVSUBARU
HndaTch627, I don't know about you, but when I get a car in under warrenty with a large evap leak DTC, it gets a canister shut off valve. That or a purge valve! Especially when it's slow!
yeah we get alot of those on the accords...they had a problem with them...winter and road salt was the prob....Evap Canister Vent Shut Valve...you guys use the same one as us....if you work for subaru that is

jeremy
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Old 12-07-2001, 09:28 PM   #14
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I work for Mercedes. Our vent valves suck! In all models!
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Old 12-08-2001, 02:16 AM   #15
HndaTch627
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Quote:
Originally posted by LVSUBARU
I work for Mercedes. Our vent valves suck! In all models!
\

LMFAO!!!!! Haha....yeah well ours only have problems on the accords cause they put them right by the rear tire and they pick up fresh air(road salt/water) and clog....actually seen an evap canister filled with water once...that was an interesting one.

jeremy
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Old 01-15-2002, 01:07 PM   #16
aspera
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P0442 Evaporative emission control system malfunction
I just got one of these from an aftermarket fuel cap. It was one of those that let you just push the nozzle through the flap. It gave a small leak that the WRX could detect.
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Old 01-15-2002, 01:34 PM   #17
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not to interrupt, but I use a Slant locking gas cap just like Peaty did and have had no problems with it on my RS.

I bought mine at Wal-Mart after leaving the stock cap at a gas station in Albuquerque. I finally threw a code just outside of Phoenix, long after I'd already refilled in Flagstaff and observed the missing cap.
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Old 01-15-2002, 09:34 PM   #18
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90% of the time the code PO440 is cause by a loose gas cap.
This could can be set if you do not tighten your gas cap all the way (3 locking clicks). The other 10% of the time it is set if the seal/vent valve in the gas cap is bad for some reason. The code will set with both OEM and aftermarket gas caps. Aftermarket gas caps are pure crap (no flames, b/c i don't care). Also note that factory gas caps have been know to go bad over time also.

In CT the emission test stations have been know to blow the vent valve while presure testing gas caps.

I must check/clear 4 or 5 CEL's a week for PO440 or PO442. Mined you I'm the service advisor and I never charge for a CEL.

PO440 = Evaporative emission control system malfunction
PO442 is a more refine version of the code (mostly MY01 and up)

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