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Discussion Starter · #1 ·
I'm not sure if this is a 5.7 specific topic or not, but here goes. Can anyone tell me what conditions have to be met so our PCMs do our evap system tests? I believe the fuel tank has to be between 1/4 and 3/4, it has to be driven on the highway for 55 mph for a few minutes, it has to sit overnight, it has to be below 90 degrees... what else? I've been meeting these conditions for a few days but my evap tests won't run. I want to get my emissions done, but this test has to show complete first. Any ideas? Thanks!
 

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Evaporative Emission System Leak Detection with Purge Monitor

This monitor requires a cool down cycle, usually an overnight soak for at least 8 hours without the engine running. The ambient temperature must decrease overnight - parking the vehicle outside is advised. To run this test the fuel level must be between 15-85% full. Criteria for EVAP monitor:

• Engine off time greater than one hour .
• Fuel Level between 15% and 85%.
• Start Up ECT and IAT within 10°C (18°F).
• Vehicle started and run until Purge Monitor reports a result.






NOTE:
If the vehicle does not report a result and the conditions where correct. It may take up to two weeks to fail the small leak monitor. DO NOT use this test to attempt to determine a fault. Use the appropriate service information procedure for finding a small leak. If there are no faults and the conditions are correct this test will run and report a pass. Note the Small leak test can find leaks less than 10 thousands of an inch. If a small
 

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The above post is the non intrusive test, if the pcm fails this test is will perform the intrusive test(even more complex) My next post is the intrusive
 

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SYSTEM





1 - Intake Manifold


2 - Throttle Body


3 - Purge Solenoid


4 - Filter


5 - ESIM


6 - Vapor Canister


7 - Control Valve


8 - Fuel Tank


9 - Gas Cap



The ESIM (Evaporative System Integrity Monitor) is very similar to the NVLD. However, the design of the ESIM has been simplified and unlike the NVLD the ESIM does not require a solenoid. The ESIM mounts directly to the canister, eliminating the need for a mounting bracket. It is critical that the ESIM is mounted vertically. On vehicles where the canister is mounted on an angle, the ESIM requires an adaptor to maintain a vertical position. When the ESIM is installed vertically, the electrical connector is in the 3 o'clock position.




EXPLODED VIEW





1 - ESIM Housing


2 - Diaphragm


3 - Switch


4 - Cover


5 - Small Check Valve


6 - Large Check Valve



The ESIM assembly consists of a housing, a small weight and a large weight that serve as check valves, a diaphragm, a switch and a cover. There is one large weight and one small weight check valve in the ESIM assembly. A seal is attached at the end of each weighted check valve. The large weight check valve seals for pressure. The small weight check valve seals for vacuum. The weighted check valves are contained within the ESIM housing.




CUT AWAY OF MODULE





1 - Large Check Valve


2 - Fresh Air Inlet


3 - Diagram


4 - Small Check Valve


5 - Vapor Canister



The ESIM (Evaporative System Integrity Monitor), while physically different than the NVLD system, performs the same basic function as the NVLD does – controlling evaporative emissions. The ESIM has been simplified because the solenoid used on the NVLD is not used on the ESIM.

The ESIM consists of housing, two check valves (sometimes referred to as weights), a diaphragm, a switch and a cover. The larger check valve seals for pressure and the smaller one seals for vacuum.

During refueling, pressure is built up in the evaporative system. When pressure reaches approximately .5 inches of water, the large check valve unseats and pressure vents to the fresh air filter.

Conversely, when the system cools, and the resulting vacuum lifts the small check valve from its seat and allows fresh air to enter the system and relieves the vacuum condition. When a calibrated amount of vacuum is achieved in the evaporative system, the diaphragm is pulled inward, pushing on the spring and closing the contacts.

The ESIM conducts test on the evaporative system as follows: An engine off, non-intrusive test for small leaks and an engine running, intrusive test for medium/large leaks.

The ESIM weights seal the evap. system during engine off conditions. If the evap. system is sealed, it will be pulled into a vacuum, either due to the cool down from operating temperature or diurnal ambient temperature cycling. When the vacuum in the system exceeds about 1” H20, the vacuum switch closes. The switch closure sends a signal to the PCM. In order to pass the non-intrusive small leak test, the ESIM switch must close within a calculated amount of time and within a specified amount of key-off events.

If the ESIM switch does not close as specified, the test is considered inconclusive and the intrusive engine running test will be run during the next key-on cycle. This intrusive test will run on the next cold engine running condition.

Conditions for running the intrusive test are:

• After the vehicle is started, the engine coolant temperature must be within 50°F (10°C) of ambient to indicate a cold start.
• The fuel level must be between 12% and 88%.
• The engine must be in closed loop.
• Manifold vacuum must be greater than a minimum specified value.
• Ambient temperature must be between 39°F and 98°F (4°C and 37°C) and the elevation level must be below 8500 feet (2591 meters).

The test is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the switch does not close, then a general evaporative failure is recorded. The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Even when all of the thresholds are met, a small leak won’t be recorded until after the medium/large leak monitor has been run. This is accomplished by the PCM activating the purge solenoid to create a vacuum in the evaporative system. The PCM then measures the amount of time it takes for the vacuum to dissipate. This is known as the vacuum decay method. If the switch opens quickly a large leak is recorded. If the switch opens after a predetermined amount of time, then the small leak matures. If the medium/large leak test runs and the ESIM switch doesn’t close, a general evaporative test is run. The purge solenoid is activated for approximately 10 seconds, increasing the amount of vacuum in the system. If the ESIM switch closes after the extended purge activation, a large leak fault is generated. If the switch doesn’t close, a general evaporative system fault is generated.

The purge monitor tests the integrity of the hose attached between the purge valve and throttle body/intake. The purge monitor is a two stage test and it runs only after the evaporative system passes the small leak test.

Stage one of the purge monitor is non-intrusive. The PCM monitors the purge vapor ratio. If the ratio is above a calibrated specification, the monitor passes. Stage two is an intrusive test and it runs only if stage one fails. During the stage two test, the PCM commands the purge solenoid to flow at a specified rate to force the purge vapor ratio to update. The vapor ratio is compared to a calibrated specification and if it is less than specified, a one-trip failure is recorded.

The ESIM switch stuck closed monitor checks to see if the switch is stuck closed. This is a power down test that runs at key-off; when the PCM sees 0 rpm’s, the purge solenoid is energized for a maximum of 30 seconds, venting any vacuum trapped in the evaporative system. If the switch opens or was open before the test began, the monitor passes. If the switch doesn’t open, the monitor fails. This is a two-trip MIL. The star scan tool can be used to force the ESIM switch stick closed monitor to run.

The PCM also uses the ESIM to detect a loose or missing gas cap. The PCM controller looks for a change in the fuel level (25% minimum) and then gas cap is loose or missing. If a medium/large leak is detected, a loose gas cap light illuminates and a pending one-trip fault code is set. On the PCM, this is a three-trip fault before the code matures
 

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P0456 DODGE Description The Evaporative emissions system is design to prevent the escape of fuel vapors from the fuel system. Leaks in the system, ca allow vapors to escape into the atmosphere. The leak detection system tests for EVAP system leaks and blockage.

During the self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it. If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.

Have you checked your Canister Purge Valve ?

https://www.youtube.com/watch?v=-MaaY_o6vPQ

https://www.youtube.com/watch?v=U7EV4BuhUco

Read more: https://www.autocodes.com/p0456_dodge.html
 

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Discussion Starter · #7 ·
Purge valve is new just yesterday. My AE is showing that it's not even trying, if I'm interpreting the data correctly. It is showing that the NVLD has cycled once, and it looks like it doesn't like the "purge valve fraction" number (I don't know what that is or what it means).

Maybe I should just give it more time?

This is a new build, and I've only been driving it with no codes for maybe 3 or 4 days.
 

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Discussion Starter · #8 ·
I could never get that test to finish. No codes, no problems, it just always said “incomplete” so screw it, I went to get emissions checked yesterday and after a million years it seems, it only failed for a gas cap. I went and got a OEM cap, and, re-tested and it passed today! I checked my monitors and now they’re all green. Maybe the emissions guys did something to make it finish? No clue there. Oh well, one step closer to done on this truck ?
 
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