Will Moser

I've been getting this code intermittently for over a year, but need to pass emissions soon, replaced the vapor solenoid multiple times now with no change. After engine warms up I can feel the solenoid clicking. Was also able to start the solenoid with a scanner as well but for some reason after hitting stop test it would continue to run until I powered off the jeep. Pink wire is continuous to the ECM plug, get 12v from white and pink has ground when powered off but do get 5v from pink when key set to on and not running. A year ago the cei would be gone for months which is how I passed my previous emissions, recent months its gone for a few days then come back but recently it seems to be more consistent, have cleared it a few times but comes back after a couple starts. Is my PCM on its way out or am I missing something? Thanks in advanced for the help.

lawsoncl

Since you're replaced the valve a few times, I would inspect all of the lines to it, including back to the tank. Sometimes the line rusts through or the rubber rots and you get a leak, or something is plugged. I believe that code is triggered when the fuel tank pressure sensor doesn't register a change when the purge valve is activated. I also got similar codes on a Nissan Frontier that the canister by the tank would get plugged up with dust every few years.

Will Moser

Thanks I'll give it a try, ordered new vacuum lines and canister. I assumed the code had to be electrical since it says open or shorted condition but it not measuring any changes makes sense especially since my xj does not have a ldp.

Will Moser

Replaced the canister but code came back a few hours later, started checking the lines with a brake bleeder hand pump after blocking one end of each line to see if they hold vacuum and there it was, the damn line going from the purge solenoid to the intake manifold had a leak. Replaced the line and this code has yet to come back. Thanks again!!!

Will Moser

I spoke too soon..... Code literally just came back ughh. I'm quite sure there are no leaks in the vacuum lines now as I tested all besides the one large guy that just goes from the canister to a vent/plug under the hood. Any other ideas? I haven't dropped the tank to check but pulling on the vacuum lines that goes to it it seems to be connected.

Will Moser

The check engine light does not come every time I start the jeep, seems to only be on like 50% of the time. Also I have noticed recently when the engine is cold it can crank for 30 seconds before actually starting. Is the ECU is on its way out?​​​​​​

Will Moser

It took a bit to start this morning and then ran fine. Just tried starting it again a few minutes ago and it was the same, took 20-30 seconds to crank but now this time a second code has come up. P1391, intermittent loss of crankshaft position sensor. Again it runs fine after it struggles to start.....

Will Moser

Since I saw that 5v on what's supposed to be the switched ground for the EVAP solenoid, seems like either the ECU is shorted or the wire is somehow shorted to the ECU sensor 5v output causing the cps code? I am trying to avoid opening up the factory wire sheath as it looks to be all intact so I ordered a reman ECU, wish me luck haha

awg

just before you install the new ECU, I would take that opportunity to probe between the ECU plug and solenoid plug to see if you have a short

there s a few ways to try, a multimeter being the most obvious

shake the harness

(the most clever method I read about involves installing a flasher relay and shaking the harness, when it stops clicking, you found the short)

(at least some) XJ have poor quality wiring, the plastic insulation is both soft & brittle

Will Moser

I tested for continuity between both plugs and it seemed fine I think or is there a better way to test it with a multimeter?
Also an update, I ended up replacing the CPS sensor the other day which made that code go away and helped for a day or two but the issue came back again this morning, didn't want to start but finally did. Starts fine when engine is warm still. But now the check engine light is no longer lit as of this morning even though my reader still shows the active EVAP code.

Will Moser

Still haven't received the replacement ECU I ordered, but I'm about ready to rip the whole engine harness out to go over it as it just keeps getting worse. Yesterday I started getting codes P0352 & P0353 for ignition coil 2 and 3 primary circuits and now today I'm also getting P0340 for no cam signal at PCM. Still have the P1391 for intermittent loss of CMP or CKP as well. Is there any sense in replacing the cam sensor or is this definitely going to be a wiring harness issue? Its getting more difficult to get her to start, have been shaking harnesses and replugging plugs and sometimes I get lucky and she will run fine but all codes are still active.