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Discussion Starter #1
Truck check engine light came on today when I hooked up my OBD2 tool I got a generic p0440 evaportive emisions error code any clues where to start on this one ?
 

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P0440-GENERAL EVAPORATIVE SYSTEM FAILURE indicates that the PCM (powertrain control module) does not see the ESIM (evaporative system integrity monitor) switch close during the medium / large leak test. That means the system is checking for minute leaks in the evaporative emissions system between the fuel tank, vapor canister and engine intake system.

You need to check all the evaporative emission system hoses on the fuel tank, vapor canister, ESIM device, and the vapor lines and vacuum lines to the engine compartment. Look for cracked and/or frayed hoses. Make sure the hoses at the vapor canister and ESIM device are sound and not leaking. Also check the fuel tank cap and make sure it is tightened securely and its seal is not damaged.

There is an electrical connector at the ESIM device. Make sure its electrical contacts are clean.

The ESIM device is mounted on the vapor canister and is near or around the fuel tank and must be oriented vertically.

Since this is a 4 year old vehicle I suspect that the vapor emission hoses will be in good condition. The ESIM device can be troublesome in that the switch contacts close during the vapor leak test but slight corrosion prevents a tell tale trace electrical signal from being sent to the PCM. Since the PCM does not get a satisfactory signal during the test code P0440 is set.
 

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Thanks all hoses look good cleared code and test drove has not happened again this was 1st time started out my driveway cold with no warm up.
and it's a bit of a pull up the far side. was also very high humidity so for now it's wait and see but will check esim connections etc as time permits thanks.
 

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thanks Allan will try to locate now that I can move again got some cracked bones in neck so sometimes have to stay immobile with brace on for a few days.
 

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well took it to dealer did smoke test, nothing wrong however ecm was 4 updates behind ( I bought used in Dec.) so after smoke test and update and new fuel cap everything was fine for over a week and now when I start it in the morning I get the P0457/or P0456 evaportive emission leak (fuel cap loose or off) seems to only happen first time I start it then if I clear code stays cleared till next morning.
 

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this problem still ongoing smoke test showed nothing, and it's been to dealer twice and they can't seem to find out why other than the irritation of the check engine light and the P0456 & sometimes P0457 nothing seems to be wrong with it. I did put in a high performance air filter (K&N) I'm ready to pull it and put a paper filter back in untill this problem is resolved.
 

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This originally started with P0440 (ESIM failure). Is that code now gone and replaced with P0456/P0457? Was the ESIM replaced?
P0456/P0457 are small leaks. The ESIM can detect leaks as low as a .010"-.020" pinhole. That is pretty small. It would be difficult to see visually and the 'smoke test' is the best method for finding these.
The PCM is likely telling the truth that there is a true 'small evaporative' leak. I have never seen one lie.
You might want to gather your service documents related to the evap problems, discuss the next step with the service manager and ask the service dept. to have another look.
They should waive the diagnostic fee if this is a return visit for the same problem (within a year). They have the smoke machine and the best chance of finding this. Much better than anyone could in the driveway anyways. Something is being missed or overlooked.
There is a small leak and a good technician should be able to find it. Some leaks are hard to find and sometimes the fuel tank has to be lowered to see it. Some joint in the evap plumbing is loose or a hose is breeched, etc.
 

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Discussion Starter #9
codes come and go on this one no rhyme or reason but did another smoke test still no results going to try that $22.00 part since it's cheap and i'm tired of driving 40 miles to get to the dealer, may have to go see now I have a sysyem failure warning on my TPS
 
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