4th gen EVAP leak detection pump test

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Curt Gobbell

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If I remove my evap leak detection pump from my 2014 ram 1500, and apply 12v dc across the 2 terminals, should I hear the solenoid click?

I ask, because I did just that and heard/saw nothing move. So I'm wondering if the LDP is the cause of my p0456 code.
 

Tach_tech

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The purge solenoid is PWM controlled, so just applying 12v likely won’t do anything and could damage it.

That being said they are prone to leaking internally and will cause a evap leak.
 
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Curt Gobbell

Curt Gobbell

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Tach_Tech,

I'm not following your logic. What does the 'purge solenoid' (under the hood) have to do with the 'leak detection pump' (above the gas tank)?
 

Tach_tech

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Tach_Tech,

I'm not following your logic. What does the 'purge solenoid' (under the hood) have to do with the 'leak detection pump' (above the gas tank)?
Sorry, my bad. For some reason I thought you had said purge valve.

The ESIM(leak detection pump) is just a switch. It registers opened or closed depending on the state that the plunger inside it is in. So applying power to it will do nothing, since there is no solenoid inside it.
 

GTyankee

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ESIM, how to replace & other things to look at


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A video on what i think Tach_tech is referring to
The video is actually a class about the ESIM

 
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Curt Gobbell

Curt Gobbell

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GT Yankee, the ESIM video states that his LDP has a solenoid that should activate when 12v is applied to the LDP terminals
 

Tach_tech

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GT Yankee, the ESIM video states that his LDP has a solenoid that should activate when 12v is applied to the LDP terminals

If that video says that he is wrong. The ESIM works off vacuum, depending on the state of the system the plunger in the ESIM will be in either the open or closed position.

This is from the service manual. It will give you an idea of how it works. There is no solenoid.

The ESIM is configured with a normally open vacuum switch and normally closed vacuum relief and pressure relief valves (see figure above). The PCM uses the ESIM for all system leak diagnostics (P0440, P0455 and P0456). The relief valves regulate the system pressure between approximately 250Pa and -500Pa.

  • When the system vacuum reaches between (-187Pa) and (-250Pa) it acts on the diaphragm and closes the vacuum switch. When the switch closes it allows continuity between the terminals. This allows the ESIM Signal to pass through the switch, pulling the signal low to ground. The PCM monitors the signal to determine the state of the switch (open or closed). The ESIM Signal can be a 5.0 volt or 12.0 volt signal depending on the vehicle. When the PCM reads voltage on the signal circuit it determines the switch is open and when the signal is pulled low the PCM determines the switch is closed.
  • The vacuum relief valve is intended to maintain the seal on the system during engine off events. However if the vacuum exceeds the regulation point the valve will pull off the seat to protect the system from excessive vacuum conditions. During purging, the vacuum relief valve inside, the ESIM is opened allowing fresh air to be drawn through the fresh air filter and Charcoal Canister to aid in drawing the fuel vapor from the canister.
  • The pressure relief valve limits any pressure build up in the Fuel Tank during refueling and allows the tank pressure to normalize during increasing temperature events. This is additionally beneficial because it achieves a switch closed state (pass threshold) sooner than if the tank has to decay from a much higher pressure.
 
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Curt Gobbell

Curt Gobbell

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So, I finally figured out what was causing my P0456 and P0457 codes.....my ESIM was bad!

Here is the backstory timeline:
Feb21 - P0456 and P0457 codes show up :(
Mar21 - replaced gap cap (twice) - no improvement :mad:
Mar21 - replaced ESIM with new unit - no improvement :confused:
Apr21 - replace purge solenoid - no improvement o_O
Jan22 - had EVAP lines smoke tested - no leaks (at this point I'm thinking "could the replacement ESIM be faulty?":Angry:
Jan22 - removed ESIM and performed the test below - bad unit :banghead::banghead::banghead::banghead::banghead::banghead:

Moral of the story...test the part before performing the random replacement procedure :rolleyes:
 

motox155

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Similar story here. I got the dreaded gas cap alarm and a CEL. Scanned my codes and got po456. Replaced the gas cap, no improvement. Bought a Mopar gas cap, no improvement. Did a little research and saw it was usually the LDP. Replaced it and cleared the CEL. The gas cap alarm went away in a few miles but about a week later CEL returns. Replaced purge solenoid and Charcoal canister, cleared CEL, same deal about a week later. Now I'm getting frustrated. One last thing to try before dropping the gas tank to look for leaks, I doubled up on the gas cap gasket to get a better seal. It's noticeably tighter when ******** down. Within 10 miles it was cleared of codes and has been that way since.
 

rmcollins3

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Sorry if I'm hijacking the thread, but I didn't want to start a new thread when there are already so many with the same issue.

Keep getting the CEL and Gas Cap message after about a month of messing around with it. So far I have (in order):

1) Replaced gas cap
2) Replaced Evap Leak Detection Pump (ESIM) at top of gas tank
3) Replaced Purge Valve

After each job I disconnected the negative battery terminal for about 30 seconds and it got rid of the CEL and Gas Cap message, but it came back after a few days each time. I did them all at different times hoping to nail down the actual issue and keep costs low (although everything was less than $100 total). Anything left to try before taking it in? I'm about at the limit of my mechanical abilities.

Should I leave the battery disconnected longer (15 min or so)?? EDIT - 2016 Ram 1500 5.7 HEMI with approx 110k miles if it matters.
 
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