Jeep is pulling the p0440 general evap failure. I have looked around under the jeep but can't find anything loose or broken. Haven't been offroad recently so doubt something broke. Any ideas on where to start checking?

 

have a real good look at the evap. canister and all the hoses to and from it. it is possible that it failed on the inside and you won't find anything. good luck

 

I am going to check it all again. I read one of the vent tubes isn't rated for gasoline and can fail so I will check that one really good.

 

if all lines are good and everything looks ok it is prob the leak detection pump. its on the evap canister with the electrical plug. dont know if they changed the name of it but thats what it was called when i worked at chrysler.

we would run a smoke test which puts a white smoke into the system to find leaks. if no leak was present we change the pump and all good.

 

I will look into that pump if I can't find a leak. Any way to test this pump?

 

i am sure there is but i dont know. it gets an internal leak. i think there is a diafram type of valve in it and it leaks. its internal so u would not see anything on a evap smoke test. if u got a warranty take it to the dealer.

also check to make sure the purge solenoid under the hood is clicking when engine is running.

edit... it does not click like the older style solenoids. i just went to check mine. also its located between the battery and the fuse box.

 

I had a series of check engine issues a few months ago and it turned out, after multiple dealer visits, that the ECM was installed upside down at the factory and that caused some switch to engage that should not have. I also read about the same thing with other JK owners on this forum...could be that....that's my guess.

 

Well, I checked the lines again and they all seem good to me. I don't know if I should spend money replacing parts that may or may not be bad, or just take it in to have it looked at. Warranty is up so they are going to run me through the ringer if I take it in.

Do you know if the purge solenoid can be tested? Maybe they are cheap to replace anyway.

Any chance the gas cap could be the problem. I know if I leave the cap off the display says gas cap but what what if it was just starting to go bad?

 

Well, I looked up the parts and I can darn near replace all the parts and lines in the emissions system for under a couple hundred. Maybe I will just start buying one at a time until I figure it out. Don't have to take it in for emissions inspection until november so I got some time.

 

P0440-GENERAL EVAP SYSTEM FAILURE


Theory of Operation

The Evap Purge Monitor tests the integrity of the hoses/tube between the throttle body/intake and the fuel tank. The monitor is a two stage test and runs only after the Evap system passes the small leak test. Stage one is non-intrusive. The PCM monitors the purge vapor ratio and the ESM switch closed ratio. If the purge vapor ratio is above a calculated value, the monitor passes. If the ESM switch closed ratio is greater than calculated value when purge flow is greater than a minimum value, the monitor passes. Stage two is an intrusive test and runs only if stage one does not pass. The PCM commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The ratio is compared to a calibrated specification. If it is less than specified, a one trip failure is recorded. This test can detect if the purge hose is off, obstructed, or the purge valve is not operational.


When Monitored:

Engine running after a cold start with the difference between ECT and AAT is less than 10° C (19° F). Fuel Level between 12% and 88% full. Manifold vacuum greater than a calculated minimum value. Ambient Temperature between 4° C and 32° C (39° F and 89° F).

Set Condition:

When the monitor conditions are met, the PCM will ramp in purge flow. If the PCM does not sense an ESM switch closure after a calculated amount of purge flow accumulation, an error is detected. Two Trip Fault. Three good trips to turn off the MIL.

Possible Causes

EVAP PURGE SOLENOID VACUUM SUPPLY

EVAP PURGE HOSE/TUBE AND FRESH AIR FILTER OBSTRUCTION

(Z905) GROUND CIRCUIT OPEN

(K107) ESM SIGNAL CIRCUIT OPEN

EVAPORATIVE EMISSION LEAK

EVAP SYSTEM MONITOR SWITCH

EVAP PURGE SOLENOID

POWERTRAIN CONTROL MODULE (PCM)