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Discussion Starter · #1 ·
On the road this week. My beloved 08 JK went over for a little state of Texas safety inspection right before I left ... and failed.

The check engine light wasn't on but it had been. I cleared with my little reader but they said it has to be off for a 100 miles.

Great ... drove it 200 miles this week and no light. YAY!

Cranked it today to get ready to go home for Texas and it's back. :pullinghair: My reader gave me the 300 whatever code (IIRC) that says emission system issue. Someone had posted a whole thread on how they solved it and I read through that. I have visually inspected for leaks and didn't see any. Try to screw gas cap on tight. I've done everything short of a smoke test.

What is causing this is one question, but more importantly (right now) what can I do to get through a safety sticker inspection and get the sticker?! My jeep fund is going to take a hit if I get ticketed for no sticker next month... Your thoughts and ideas needed. Thank you!
 

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What's the actual code it's popping? PO300 or what?
 

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Discussion Starter · #3 ·
What's the actual code it's popping? PO300 or what?
Oh boy ... I know someone would ask that and I don't have my reader with me ... but then I remembered I had taken a pic of it. FOUND IT. Not 300 something!

Here it is:

P0456
Evaparotive Emission Systems Leak Detected (very small leak)
 

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Oh boy ... I know someone would ask that and I don't have my reader with me ... but then I remembered I had taken a pic of it. FOUND IT. Not 300 something!

Here it is:

P0456
Evaparotive Emission Systems Leak Detected (very small leak)

Definitely helpful to have the code :p


Probably want to check the gas cap again and make sure the rubber seal isn't shot. Next thing would be have you moved or replaced your evap canister at all? Might be worth a crawl under the jeep to check it out and ensure all the tubing is snug and no leaks or issues present, and double check the electrical connector down there. From there you can trace the hose forward to the engine bay and have a looksie along the way to see if there's any glaring issues.


Just as an aside here - the parts to replace along that path are fairly inexpensive and there's lots of videos on youtube on how to do it if you're comfortable with basic tools.
 
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Discussion Starter · #5 ·
Watch vids and learned a lot. Someone had a very similar error code but it wasn't "very small leak" but "gross leak detected" - P0455. Does that mean this is just my gas cap or is the code not that specific?
 

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Watch vids and learned a lot. Someone had a very similar error code but it wasn't "very small leak" but "gross leak detected" - P0455. Does that mean this is just my gas cap or is the code not that specific?

It's not that specific unfortunately. The seals between various parts tend to be the culprit. Just start at one end and work you way forward. Preferably with a 12 pack of beer for moral support.
 

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I am having the identical problem and need the sticker by Monday. Went the new $31 gas gap from the dealer and no joy. :pullinghair:
 

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Check at the top of the gas tank where the evap canister plugs into the top of the tank. A lot of times those break off and you have to use a splice to connect t it back up (make sure the splice isn't too small or it messes with the gas pump and makes it think the tank is full)
 

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Discussion Starter · #9 ·
It's not that specific unfortunately. The seals between various parts tend to be the culprit. Just start at one end and work you way forward. Preferably with a 12 pack of beer for moral support.
Dumb question: are those seals like gaskets that need to be replaced or are you talking about just going through it making sure the hoses are seated well and haven't worked their way loose?
 

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Dumb question: are those seals like gaskets that need to be replaced or are you talking about just going through it making sure the hoses are seated well and haven't worked their way loose?

It's plastic hose, and plastic joints. I fixed mine by wrapping it with electrical tape. The problem popped up after relocating my evap canister. The new section was all OK, it was part that I didn't touch, but pulling on the hoses must have loosened it.
 

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Can't say its the same as GM's but on GM's that evap test is only run when the tank is between 3/4 and 1/3 full and only after it has been off for a bit. Basically they put a vacuum on the tank, then check after a while if it leaked down a lot, or a little, or not at all.

*hint* (Keep a full tank for the 100 miles after you clear it. Then go get your sticker. :))
 
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Dumb question: are those seals like gaskets that need to be replaced or are you talking about just going through it making sure the hoses are seated well and haven't worked their way loose?
check between the ESIM module (part number from Autozone is ESIM1000 IIRC) as there is a gasket that I pinched by accident when replacing my ESIM unit when I reattached it to the canister, if it is twisted or pinched it can cause the CEL to pop on, forget what code I was correcting at the time but it was for a failed ESIM unit/failed evap test
 

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Well I went out last night and started the Jeep and the light is gone. Shut it off and started again and still not there. Tank is near empty as warning light has appeared.

Will head for a sticker this morning and see what happens. I read somewhere that if you don't drive 100 miles after it resets that the inspection machine will pick that up and still issue a fail notice.

We shall see.
 

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That is correct. The test basically says 'any code and greater than 100 miles since last reset', 101 and your good.
 

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Anytime you clear codes with a scanner, it will erase all of your emissions statuses and you will have to drive for a while for the OBD2 "readiness" to be established for each system. This includes your evap systems, as well as a plethora of other things (O2 sensors, catalyst efficiency, misfires, fuel system, etc.).

Your evap system takes the longest to test "ready" after a reset because it works different from the other systems. The others will check "ready" pretty quickly after driving for 50 miles or so. The evap on the other hand requires a few driving cycles, including an extended vehicle off period, where a vacuum pump will pull vacuum on the system and check that the vacuum pressure is maintained. A small leak fault happens when there is a pinhole leak in the system, or if the gas cap seal is beginning to fail. If it says large leak, then basically the system cannon pull vacuum at all. That suggests that something is broken or disconnected, or just that the gas cap wasn't reinstalled/left very loose.

I always recommend that people buy a cheap Bluetooth OBD2 dongle from Amazon, and purchase the Torque Pro app on their phones. Should cost you less than $30 all in, and will work for every car you own (1996 model or later).
 

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Well FWIW, I did not reset any codes by pulling the battery cables nor did my friend reset the code once his scanner made the evap leak reading.

Went to the inspection station and the tech again reiterated that unless one drives 100 miles after a reset that the machine will still read a problem but took the Jeep in anyway. Joy of joys, my Jeep passed today and the report from the inspection station showed that I had driven 272 miles since the last reset.

Apparently replacing the gas cap to remove the warning light does not require a 100 mile drive afterwards. Since no one had reset the computer the fault cleared right away. :bop:
 
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Discussion Starter · #17 ·
got the code reset and drove it 98 miles. we'll see in the morning if I can get a sticker out of this... stopped twice and kept the fuel tank nice and full!
 

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Apparently when I installed my ham radios a few weeks ago I cleared any stored codes when I disconnected the battery cables. The sheet from my inspection station showed that I had driven 272 miles since the last reset.

Since adding the new cap I had only driven about 10 miles but the light was still on when I got home. The next morning I started the Jeep and the light was out. Shut it off and started again and no light.

Apparently the Jeep only needs to sit overnight to clear the engine light when replacing the gas cap. Have a sticker so good until next year. :bop:
 

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Discussion Starter · #19 ·
FAILED AGAIN.

Check engine light NOT ON. Drove it 103 miles. It fails. It failed because it says the "Catalyst" was Not Ready and the 02 Sensor was Not Ready.

What does this even mean? How do I get them ready without that infernal check engine light coming back on?
 

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Did some looking around and it seems you have to put a specific type of mileage on it and not just go for a drive.

https://www.jk-forum.com/forums/stock-jk-tech-12/08-jk-wont-pass-tx-inspection-02-catalyst-show-not-ready-210942/#post2755980

Verify no codes are set. This may require more than one code reader. Not all code readers will see all codes.

According to the '08 service manual, this is what's required to set the
Catalyst / O2 Monitor
The Catalyst and O2 Monitor information are acquired and processed at the same time. Most vehicles will need to be driven at highway speed (less than 50 mph) (73km/h) for a few minutes. Some vehicles run the monitor at idle in drive. If the vehicle is equipped with a manual transmission, using 4th gear may assist in meeting the monitor running criteria.
Engine RPM between 1200 to 3000.
Engine temperature greater than 70°C (158°F)
Engine run time greater than 92 seconds
MAP between 10 - 20 kPa (7.5 - 15 Hg)
Vehicle speed between 20 - 70 mph (29–103 km/h)
 
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