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Old 05-14-2014, 09:39 PM   #1
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EVAP code causes and fixes

My 2000 TJ (6-cyl) has been throwing an 0455 code at odd intervals.

You'd think, it being a "large leak" code, that it would just come back after I reset it. But it doesn't. Sometimes it goes 1000 miles or more before the light comes back on. I've also gotten a simultaneous "small leak" code -- and I don't see how the system can tell there's a small leak if there's already a large leak. So I'm suspicious of EVERYTHING.

I've checked all the under-hood hoses and they look OK; I also replaced the gascap (goddam factory cap cost me $26 at the stealer's !!!)

SO -- what's next ? Take it in for a "smoke test", or replace whatever passes for a sensor ? (And just WHAT is the sensor?)

Thanks...

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Old 05-14-2014, 09:46 PM   #2
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I chased this on a 02 Dodge truck for a year and it turned out to be a bad PCV valve but our TJs don't have one. Does the oil filler cap seal good? Also, make sure the breather tube/elbow near the rear of the valve cover isn't plugged or cracked. Also have seen E3 plugs on a 4.0 cause these codes (friend of mine). Again, never seen it on a TJ but many GMs will get EVAP codes when the purge valve is failing. Maybe check the vent line from your filler neck to the tank also.

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Old 05-14-2014, 10:30 PM   #3
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Leak detection pump. I chased that code for months. Took it in for a smoke test, and they found the inside of this pump was packed solid with mud.
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Old 07-08-2014, 08:56 PM   #4
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Ryan- can you explain all of this in a little more detail? I'm getting the same code and was told exactly what you just said.... I just have no clue what you're talking about. Thanks in advance!
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Old 07-08-2014, 10:15 PM   #5
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A smoke test is performed usually by a mechanic with a smoke machine in the shop. There is a port on your evap system that the machine hooks up to. They pressurize the evap system with said smoke machine. Then obviously where there is a hole/crack or whatever smoke will come out.
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Old 07-09-2014, 05:38 PM   #6
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Quote:
Originally Posted by TMTMTL View Post
Ryan- can you explain all of this in a little more detail? I'm getting the same code and was told exactly what you just said.... I just have no clue what you're talking about. Thanks in advance!
I'm by no means an expert on this, just repeating an explanation passed on to me.
At each start up, the leak detection pump (LDP) pumps a slight bit of air into the vapor recovery system to check for leaks. If it notices a immediate drop, it will continue to pump air to determine large vs small leak. If the pump is bathed in mud and water, it may hinder its operation. On my '01, the LDP is under the hood on the drivers fender. Other years, it is located in the rear passenger fender, behind the plastic liner. I forget the price on the new pump, but it was well worth pulling off the old one and cleaning the gunk out of it. Trace all the lines out and check for dry-rot while your in there.
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Old 07-09-2014, 05:50 PM   #7
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That goberment mandated pump is only on California emissions TJ at least thru 2004
Not so sure about 05 06

My 04 federal emissions rubi no such pump
My 98 calif emissions sport has that pump

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