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Unread 01-03-2005, 06:11 PM   #1
holmes133
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Evaporative Emission Control System Leak ..HELP!!!!!

My wife's 2002 4.0 has had the check engine light come on twice now. Both times I checked the codes and it read P0455 (Large leak detected). I have checked all of the hoses and lines and can't find any that are loose or cracked. I reset the codes and the light goes out...but after a couple of days driving it will come back on again. The WJjeeps site has a list of all the codes and a good description of what the probable causes are. I think I am dealing with some type of internal leak here, possibly caused by a Duty Cycle Purge (DCP) valve. Has anyone else had a similar problem? Can anyone tell me what this thing (DCP valve) looks like and where it is. The local dealer here wants $14 for a new one, so I thought that was a pretty fair price to just shotgun one of these things in hopes of it fixing my problem. Any and all advice will be greatly appreciated.

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88 YJ with a 78 258 bored .030 over,Weber,Nutter Bypass, Juice Box and Herculined. Paint Job, 2.5 lift and tires coming in the near future!

2002 WJ Limited, 4.0...all stock...the wife's car!
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Unread 01-03-2005, 10:30 PM   #2
Meerkat
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It sounds like you are on the right track.
Not too sure about your year, but the valve you are looking for should be on, or near, the charcoal cannister. Probably on the driver's side, front, underneath and just behind, the bumper..

HTH
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Black 1996 5.2L ZJ Limited
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Unread 01-04-2005, 06:30 AM   #3
holmes133
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Thanks for this Warren. Come to think of it I did follow an emissions related hose(tube) all the way to the front on the passengers side underneath the battery tray. I physically felt the hose and the connection, but had no idea of what I was actually touching! I guess I will hit the delaership up today and just change the thing.
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88 YJ with a 78 258 bored .030 over,Weber,Nutter Bypass, Juice Box and Herculined. Paint Job, 2.5 lift and tires coming in the near future!

2002 WJ Limited, 4.0...all stock...the wife's car!
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Unread 01-04-2005, 01:44 PM   #4
greasefingers
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I had a crack in my charcoal canister once. It was not a Jeep but instead of buying a new canister, I fiber-glassed the crack to seal it.
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Unread 01-04-2005, 02:00 PM   #5
Larry harvey
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Holmes133.................

Generally this code has to do with a small leak at the gas refill cap. Make sure the gas cap is tight and/or a good seal. If you do not have a scantool to clear this code, you can try a couple of turn key starts and the code may clear. Also after approximately 40-50 starts the code should clear and the CEL should go out if this is the issue.

Larry
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Unread 01-05-2005, 06:49 AM   #6
holmes133
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The gas cap was the first thing I checked....even accused the wife of driving with it off! Not a good move on my part! Will a cracked canister cause what appears to be an intermittent fault? I would think that a cracked canister would cause the light to always be on. As for clearing codes, when I disconnect the negative battery cable and leave it disconnected for 10 seconds or more, will that not clear the code? The last two times I have done that and then checked the codes and done is the only thing that comes up on the screen.
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2002 WJ Limited, 4.0...all stock...the wife's car!
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Unread 01-07-2005, 01:11 PM   #7
Larry harvey
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Evaporative System Leak

Holmes133..................


FYI


2500401 - TROUBLE CODES CAUSED BY AN EVAPORATIVE SYSTEM LEAK
Date: 05/11/01

Model year(s): 1999-2001

Description: Additional diagnostic for diagnostic trouble codes caused by an Evaporative System leak. This bulletin involves information which may be of assistance when diagnosing the vehicle evaporative system for a possible leak source and its cause.

Details: DTC P0442, P0455 or P0456 are all diagnostic codes indicating a leak has been detected in the EVAP system. The bulletin points out that, while most leaks will be external such as a loose gas cap or damaged hose, internal leaks also are possible. The most likely source of an internal leak is the Duty Cycle Purge valve (DCP). This valve could be stuck open due to corrosion, dirt from outside or debris from inside the system, such as charcoal from the vapor canister. The DCP valve is tested by on-board diagnostics only after the Purge Flow Monitor is passed; if that monitor fails, the DCP valve will not be tested. The bulletin offers helpful tips for troubleshooting and understanding the logic of the EVAP diagnostic routine


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2500102A - MIL ILLUM., DTC P0442, P0455, OR P0456 - LEAK DETECTION PUMP, LEAK DETECTED
Date: 9/02/02 (supersedes 2500102 dated 2/11/02)

Model Year(s): 2002

Description: This bulletin involves a new diagnostic test for the LDP system.

Details: MIL illumination with one of the following DTC:
P0442 EVAP Leak Monitor .040 Leak Detected (Medium Leak)
P0455 EVAP Leak Monitor Large Leak Detected
P0456 EVAP Leak Monitor .020 Leak Detected (Small Leak)
If one of the above DTC’s are present, perform this diagnostic test first before proceeding with the diagnostic procedures in the appropriate Powertrain Diagnostic Procedure Manual.

Raise the vehicle on an appropriate hoist. Locate the LDP vent valve. Remove the vacuum hose from the top of the vent valve (Fig. 1). Attach a hand vacuum pump to the vent valve and apply 20” Hg. vacuum. Observe the vacuum for 10 seconds. If the vacuum holds between 15.5” Hg. and 20” Hg., refer to the appropriate Powertrain Diagnostic Procedure Manual, MDS2, or the Leak Detection Pump Operation and Diagnosis booklet (Publication No. 81-170-000606) for further diagnosis. If the vacuum drops below 15.5” Hg., obtain the appropriate LDP vent valve using the Mopar parts catalog and perform the Repair Procedure.

Repair procedure:
1. Remove the left rear wheel.
2. Remove the wheelhouse splash shield (five plastic rivets P/N 34201631) to gain access
3. Remove the hose at the top rear of the evaporative canister to ease vent valve removal.
4. Remove all clamps and all hoses attached to the vent valve.
5. Install new vent valve. Ensure all hoses, clamps and the vacuum hose to the top of the vent valve are securely attached.
6. Attach the hose at the top rear of the evaporative canister.
7. Install wheelhouse splash shield using five plastic rivets.
8. Install left rear wheel (WJ only).
9. Lower vehicle.
10. Use the DRBIII® to erase the DTC.

Parts required:
4669865 LDP vent valve



Larry harvey
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Unread 07-24-2010, 07:32 AM   #8
andrewnovell
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Confused

Hello,

So is the Duty Cycle Purge valve located inside the leek detection pump or a free standing unit? Does anyone have a clear pic of this damn thing on a wrangler 02?
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Unread 07-24-2010, 10:41 AM   #9
WiCkeDuDe
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On a wrangler or a WJ? Its done very differently on a wrangler.
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Unread 08-08-2010, 06:39 PM   #10
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