AlanP1964

2001 Cherokee. CEL was on, had scanned at AutoZone. Came back positive for P0455. Figured it was worth a shot replacing gas cap to see if that corrected the problem. Installed new gas cap, started the Jeep and CEL turned itself off (I did nothing to clear the code). Drove home, less than a mile from AutoZone. Car sat all night. Next morning I drove to work, 40 miles each way. CEL still staying off. Left work at noon and took the afternoon off. Had to run an errand that was a bit out of the way, so probably 60 miles for my trip for the errand and back home. CEL still staying off. This morning, I start it up and letting it idle while I check email on my phone. Couple of minutes go by and "Pop" CEL comes on. I stopped at AutoZone here by my office and it's throwing P0455 again. I guess anything is possible, but a new cap already leaking? I also thought maybe the guy at AutZone possibly cleared the code Tuesday but I have never seen an instance of them clearing the code. In fact I asked one time if they would and the guy said they wouldnt clear them, but I could by disconnecting the battery etc. Any thoughts? Suggestions?

xcalibur_123

I have the same problem, but i havent check the gas cap.....a friend help me with some other codes, like P0300 and P0303 and P0304, changed spark plugs and those where off, im just left with P0455 and P0136

Any suggestions?

ryan8551226

Check the lines running from your evap cannister. I believe I had that code and had to replace those lines.

Squid

EVAP system leaks can be very difficult to find. Check all vacuum lines as best you can. If you can't find it sometimes you just have bite the bullet and find a shop with a smoke machine.

xcalibur_123

Do anyone have a diagram for the vacuum lines or some pictures how to check them?

13667

I chased a P0455 for over a year on my 2000 XJ Sport until I think I finally fixed it. The code would come up and the CEL on every couple of weeks or months, and now it has not occurred in 4 to 6 months.

If you look under the hood on the passenger side near the firewall there is an evap solenoid near the leak detection pump (LDP). This solenoid has some lines coming off of it, they are hard plastic lines. One of the lines has a port on it with a green cap, the green cap may help you find the solenoid. (no insult intended, I had no idea what it was or where it was the first time I read about it) One of these lines goes along the fire wall, or maybe two of them go along the firewall to the driver side and then run parallel to the left side of the engine and then connect to the intake manifold via a 90 degree rubber hose like connector. Check this connector by trying to pull it off of the metal fitting or nipple on the intake manifold. If it comes off easy with little pressure this could be your problem. It may be sticky or powdery and leave some black deposits on your fingers. Mine was heavily degraded. I replaced mine with a piece of straight vacuum hose long enough to make the 90 degree turn. I didn't want to try to find a new Jeep part nor did I want to pay for a new Jeep part.

As an aside, maybe my XJ is peculiar, but a few weeks ago I took the gas cap off to dump some gas in from a 5 gallon can. After doing so I forgot to install the gas cap and drove the car about 4 miles without the CEL coming on. Before I left to make the 4 mile trip home I noticed that I left the gas cap off and then looked for the CEL, but it was not illuminated. I know the CEL works, it comes on every time the key is turned on and then goes off.

Replacing this right angle rubber hose connector will also solve some of the leak detection pump/evap trouble codes, but I can't remember the code, but I think it is a 14XX code. My father had a 2000 XJ and it had a code and CEL that no local garages could figure out. I googled it and found a great write up on following the line to the manifold and it predicted that this same vacuum hose would be no longer connected to the manifold. It was right, I reconnected it and reset the CEL and it never had an issue again after replacing the right angle rubber hose with vacuum line.

One more aside... I used to get a P0303 (plus one other code I forgot), the CEL and a really rough idle on a hot restart, but the code no longer occurs. I will admit the engine idles a bit rough initially on a hot restart but it clears up quickly. I think this was a known issue and Jeep offered an insulator to go over the #3 injector or something.

If your Jeep ever burps or farts or coughs when it starts it can blow this hose off of the intake manifold if the rubber is degraded.

My XJ has 154K miles in case you are wondering. When my dad's had the same issue it had about 130K miles.

Sorry for all of the pontification, short answer is look at the rubber right angle vacuum line on the end of the plastic tube coming from the evap solenoid and see if it fits loosely onto the intake manifold or appears to be degraded (dry, cracked, transfers black junk to your hands).

If you want any diagrams or pictures PM me your email, I can't figure out how to post a picture here.

Good luck, I hope it is this simple for you.

13667

Found this on another forum just now while trying to find the post that led me to the issue initially on my father's jeep. It's not my own material credit given to two screen names below. They focus on repairing the hoses at the solenoid and along the length of the vehicle underneath.

posted by Capndave
"If the loose gascap wasn't it then I'll bet you are having the same problem which many 2001 XJ owners have.

There is a line which runs from the purge solenoid to the evaporation canister.
The line is made up 3 segements - plastic, steel, then plastic again. The plastic and steel segements are connected together using two 3" sections of 5/16th rubber hose. Those cheap made-in-china hoses are very prone to splitting. Mine split at 58,000, and caused me to throw a 442 (small leak) and eventually a 455 (gross leak).

To fix ...

Buy yourself 6" of high quality 5/16th hose, and cut it into two 3" pieces.
Crawl under the driver's side of the jeep and identify the vacuum line."

Posted by Walter Crovo
"If you follow the center hose from the evap cannister, located above the LR shock, down the frame it heads up when you get to the end of the frame. That is where the lower hose is, connecting the plastic pipe to a metal pipe, follow the metal pipe to the hose that connects it to the plastic pipe again."

Grip

good info, my 01 XJ just threw this code today.

Grip

i replaced some hoses under the rear connecting the charcole canister to the fuel tank, there were two 3" sections of rubber hose that were dry rotted.

my problem now is that i pulled the plastic tube off the top of the fuel tank when replacing one of the rubber hoses by accident, and now i cant get the damn tube back on because i cant fit my hand in there.

i tried to loosen the bolts holding the fuel tank up enough so i can reach my hand up there, but the bolts wont budge.

anyone else ever have this problem?

Squelchtone

so my Check Engine Light came on today and I went to Autozone to get it scanned. They read a PO455 and a PO303. The AutoZone guy must get a lot of this because he asked me right away if I got gas today and I got gas this weekend and didn't drive much until today, and yep, gas cap wasnt screwed on, I pumped gas and just put it on the filler tube but didnt click it.

My question is more about the PO303 code.. I just got new spark plugs 3 weeks ago and the jeep idles fine and has great pick up with no misfire that I can hear or feel, so could the gas cap thing throw both of these codes, or did the guy read an old code from before I bought the XJ a month ago?

Also, when will it turn off? I saw some forum posts saying after x key in the ignition start cycles, and some folks think it is based on driving 50 miles or more. Or should I disconnect the battery and step on the brake pedal and drain the system, wait 10 minutes, and reconnect the battery and see if Check Engine Light comes back on, or just stop by Autoznoe and ask them to reset it?

Thanks
Squelchtone

Squelchtone

quick update: I'm notoriously impatient, and got tired of looking at the check engine light, so I removed the ground wire from the battery for 10 minutes, pumped the brake pedal a couple times per someone else's recommendation in another post, reconnected the battery, started her back up and the check engine light is off now. I hope to not see it on again for a long time.

Squelchtone