for several months I get a occasion CEL which comes on and usually stays on for several days, I have a code reader and repeatedly have gotten just code P0456 and have cleared it out which last for a bit and then it just comes on again whenever. No problem with how the jeep runs this is a 2000 XJ all stock powertrain 123K. I initially thought this was a bad gas cap again, which I went through years ago and finally replaced but when I googled the code I found this type of info instead. Apparently this particular code is in reference to a very small leak of the Evap system and i'm guessing that I have a loose of pinched vac line somewhere, my problem is how to I go about methodically chasing this down???
The LDP, (leak detection pump) is located in the left/front corner of engine compartment below the air cleaner housing. It is mounted to left/front inner fender sheet metal. The LDP and LDP filter are replaced (serviced) as one unit.
But you will want to check all the vacuum lines and hoses before you replace the pump. Here is a service bulletin that will explain it better than I can.
As far as it being expensive..I don't think it would be all that much, but you have to get it from the dealer, so, that's up to them. That's how they get us, (lol)
EVAP System - Leak Detection Pump Misdiagnosis
GROUP: Vehicle Performance
DATE: Feb. 4, 2000
Misdiagnosed Leak Detection Pump Systems With DTC P1494, P0442, P0455, OR P0456
During evaporative system diagnosis, Leak Detection Pumps have mistakenly been replaced. A thorough inspection for pinched, kinked, or disconnected supply vacuum lines (as currently listed in the Powertrain Diagnostic Procedures) is a critical step in diagnosing DTC P1494 (LDP SW OR MECHANICAL FAULT). Additionally, the other evaporative leak faults (DTC P0442 - SMALL LEAK, P0455 - LARGE LEAK, and P0456 - VERY SMALL LEAK) should have the supply vacuum lines examined for pinches or kinks prior to any LDP component replacement.
A thorough inspection for pinched, kinked, or disconnected supply vacuum lines is a critical step in diagnosing................ Additionally, the other evaporative leak faults (DTC P0442 - SMALL LEAK, P0455 - LARGE LEAK, and P0456 - VERY SMALL LEAK) should have the supply vacuum lines examined for pinches or kinks prior to any LDP component replacement.
Physically trace and inspect the vacuum lines from the LDP to the charcoal cannister near the drivers side rear upper shock mount. Look for damaged hose or loose/cracked rubber fittings on the tubes.
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I have the same truck/same issue. Any chance you smell gas when you first turn it on in the morning, but then not through-out the day?
I am going to check for that kinked/cracked hose but I'm not sure where the canister is?
i have on occasion, but not every day, and the light keeps coming back on, it has even gone so long that occasionally it turns off by itself for a week and then comes back, I'll try to get a look at the canister one of these days.. I fear my coming state inspection will fail
still banging my head on this one and it does definately smell like gas on occasion when u first start up, I've looked at all the hose connections and they are all still intact, very flexible rubber, some were covered in mud, I removed them cleaned up a bit and put back on still nothing.. is the canister itself somehow suspect?
Just to confirm this, I pulled the part located under the rear of the jeep, this is the canister correct? there didn't seem to be any sign of leaking and I plugged 2 of the inlets and then used my air compressor to put about 10 psi of air into it which made is swell slightly but nothing obviously leaked, a;sp checked all the lines, they were all very good looking, not sure why but I can't find any that are dry rotted or cracked as others seem to report. There was a crap ton of mud/dirt everywhere so I cleaned all that as much as possible and reinstalled using some grease hopefully to help stop any tiny leaks. Cleared the codes stored which were the original plus the large leak which is from puttin the key to on by accident when I started and had the lines disconnected already. When I restarted I didn't get a fuel smell and no CEL light yet. I may just go buy a new MOPAR gascap in the morning otherwise I can't think of anything else to do.