F150Torqued

The Evaporative system has about 30 specific trouble codes - P044x through P046x. It does a lot of different things and remains somewhat of a mystery to many. And it shouldn't be. It is actually quiet simple. A normally closed valve (EVMV) connected to intake manifold vacuum, and a normally open (canister vent valve) beyond the carbon canister - both of which the PCM can control separately, and a sensitive tank pressure sensor so the PCM can monitor tank vacuum while it manipulates those two valves. It can tell if gas cap is missing, if there are leaks - and how big the leak is, or if the carbon canister is clogged up.

I have located and worked out Torque equations for a BUNCH of Ford 'custom' OBDII Parameter IDs for the EVAP System on my 2004 5.4L Lariat. Then put together a very informative Torque Pro dashboard that monitors everything about the EVAP system. You can WATCH it all happening - and determine what is keeping the EVAP system from completing its test. I worked out the equations and created a downloadable CSV file - for importing directly into Torque Pro for benefit of other Torque Pro users. Here's a Screenshot:



----- Brief Description of Gauges - and their purpose/meaning as to function of the EVAP Monitor. ------

Intake: Intake Air Temperature. Evap Monitor routine will NOT run below 40º or above 90º IAT.
Speed: Vehicle Speed. Evap Monitor is disabled below 40 MPH.
EVAPSOAK: Evap Monitor is disabled if engine 'OFF' soak has not been 8 hours prior to THIS drive cycle.
FLI: Fuel Level Indicator. Evap Monitor is enabled only between 15% and 75% fuel tank level.
EVAPMODE:
...-1 = Evap Monitor Not Running (disabled)
....0 = Phase 0, entry conditions not met
....1 = Phase 1, Initial Vacuum Draw down
....2 = Phase 2, Vacuum Stabilization
....3 = Phase 3, Vacuum Hold and Decay
....4 = Phase 4, Vacuum Release
....5 = Phase 5, Vapor Generation
....6 = EVAP test completed
EVMV: Evaporative Vapor Management Valve (N/C) (a/k/a Purge Valve) connects to Intake Manifold vacuum port. This valve is 'modulated' open and Fuel Tank Pressure Sensor monitored to check system integrety / leaks.
FTP_InH2O: Fuel Tank Pressure converted into Inches of Water
EVAPCV: Evaporative system Canister Purge vent valve (N/0) vents through known resistance of Carbon Canister flow.
CCL_ON: Check Cap Lamp illuminated on instrument cluster. (Remove Gas Cap & drive a short distance!)
FTP Pa: Fuel Tank Pressure in Pascals (the international standard OBDII measurement).
FTP_V: Fuel Tank Pressure in Volts.
EVAPCP: Evap canister Purge commanded
EVAPCVF: Evap Canister Vent Valve FAULT flag
EVAPCVFM: Evap Canister Vent Valve FAILURE MANAGEMENT MODE
EVAPO20D: Evap '.020' Leak Test conditions not met. (Trucks exempt from the .020" leak test)
EVAP020C: Evap '.020' Leak Test Completed. (Trucks exempt from the .020" leak test)
EVAP020R: Evap '.020' Leak Test Ready (Trucks exempt from the .020" leak test)
EVAPSTAT: Evap Monitor Test COMPLETED this Drive Cycle.

Failure of this OBD Monitor to complete is the number one cause of Emissions Readiness failure. Operating parameters are stringent. Intake Air temp must be between 40 & 90 degrees. Vehicle speed must be > 40 mph. Fuel Tank Level must be between 15% & 75% (slosh pushing either out of range will 'cance' EVAP Monitor & reset EVAP Mode back to -1. Engine soak time (EVAPSOAK) before this drive cycle must be > 8 hours. Gas Cap test on test must pass first. Of course NO component faults existing. PCM must see tank pressure begin to decline at ~50% duty cycle on the Evaporative Vapor Management (Purge) Valve. Then must step through the 6 test modes above (EVAPMODE).

The attached "CSV" file contains the "NON-STANDARD" PIDs that are not included with Torque Pro - or ANY OTHER reader that I'm aware of. (Vehicle Speed and Intake Air Temperature) are the only ones that are standard and included with Torque Pro. So the remainder must be added. The attached CSV file (named 'Monitor EVAP System v1-1.CSV') can be downloaded and copied to your android device in the android file folder named .Torque\ExtendedPIDs . Then when you go to >Settings >Manage extra PIDs/Sensors - Menu >Add Predefined Set, you can select the file by its name. Then when you go to a new dashboard page you can ADD the gauges as depicted above - or whatever type gauges you prefer.

EDIT: Correct CSV file to version '2'. If you downloaded version 1, you can download V1-2 and import it. Torque will ask if you want to keep both copies of duplicates or overwrite them ---- choose overwrite. SORRY for the error that didn't allow adding the EVMV gauge.

If you have trouble PM me or post back for assistance. This whole scheme works great with Torque for expanding its capability endlessly.

Eric Kleven

Perfect Timing! My truck started throwing evap codes last fall, just as it was getting colder than I cared for working on vehicles. Now it's warmed up and I'm sick of the light.

Thanks!

F150Torqued

My hope is that it will help someone. I'm a believer in 'challenging' sensors with some KNOWN constant (like putting cardboard in front of the radiator and seeing if the ECT reading will rise). But some are harder to read see like FTP. With this Torque Pro dashboard, you can use a piece of radiator hose over the tank filler pipe - blow into it - or such on it - and see the FTP press register the change. Logically you can figure if canister is clogged - OR vent valve is 'stuck' or clogged, or CMCV will not open when energized.

Eric Kleven

Well, mine's a P0446 Evaporative Emmissions Control System vent Control Circuit. different problem.

F150Torqued

Thanks for the feedback.

I would 'HOPE' one of my 'flags' in the lower right of the dashboard (EVAPCVF: Evap Canister Vent Valve FAULT flag, OR EVAPCVFM, Evap Canister Vent Valve Failure Mode) would illuminate.

So often (as is the case here) I am not able to 'test' those 'bit flags' when I don't have the problem with my truck. I do everything I can to verify my data, but don't wish to intentionally 'screw' something up on my truck just to see what will happen. //Even though I have been known to do that.!!!// I do challenge sensors in 'redneck' ways to make sure the PIDs are right --- FOR MY OBDII system. Though I am aware of lots of instances of non-standardization of PID assignments. The Bit map 'flag bytes' are particularly hard to figure out / verify.

I tested the 'Cap Off lamp commanded ON' flag & it works. I used an old radiator hose on the filler neck and blew air into the tank to verify my FTP sensor worked - and that the CV valve was open/clear and charcoal canister wasn't clogged. But I have never witnessed one of the failure 'flag' bits come true. I'd love to know if it does.

The Evap Canister vent valve is Normally Open - it's located around right rear frame above spare tire beyond the carbon canister. Hopefully the 'circuit' problem is just a poor electrical connection at the CV plug, or a short to ground being detected by the PCM - (ie: P0446). Unlikely, but could be a bad coil in the CV valve itself.

There are different DTC 'codes' for other flow problems like insufficient or excessive vent 'flow' determined by the PCM drawing down a vacuum in the tank then closing the EVMV (purge valve) and monitoring vacuum decay time and flow rate. So I would put high confidence in your DTC code in absence of those others. You can observe Tank Pressure and the Vapor Management routine working - but PCM is telling us it CANNOT do an EVAP leak test because it is unable to CLOSE the N/O valve beyond the charcoal canister for EVAP MODE Phase 3 test.

Ring that dude out.

Mrpriceisright

Thanks for that. I have a 2001 bifuel and most of these worked, paticularly the important ones, Intake/IAT, Speed, FLI. Evapsoak and Evapmode also worked. I didnt get anything on EVAPCV so I modified the PID to 1166 (which I believe is EVAP vent Duty Cycle and then got a reading. No EVMV either.
I also added a PID for throttle position mode TPMODW (1125) which has only 3 states, Idle, partial and WOT (values 255, 0, 1). Throttle itself quirkily shows 20% at idle.

With EVAPSOAK, IAT and FLI within correct ranges, EVAP came ready after driving for 10 mins at 45-65 mph. 👍

I should probably post something over in the 97-03 forum for reference.

mellowmaximo

I am troubleshooting an EVAP system "monitor not ready" with Torque Pro on my car. Unfortunately, it's not an F-150.. but I can learn from this thread anyway.

I think my canister is plugged, but I don't know how to definitively tell from my PiD gauges, because I don't know what the gauges show during normal operation. I started looking at them only once the EVAP problem arose. I am still familiarizing myself with how the system operates.

On the Torque Pro, I have a PiD named Canister Charge. When I make a dial to see it dynamically doing it's thing, Torque assigns it a different title: EVAP Level and it's a percentage measurement. Not sure what it's showing me or supposed to show (it doesn't go past 2.7%). How much gasoline vapor there is? I'm wondering if this PID ever goes to 100%. If so, when the EVAP DUTY CYCLE PID is showing me the purge valve is 100% open, and PID EVAP VP (EVAP system vapor pressure) is pulling into a vacuum because purge is open , then the PID CANISTER CHARGE should go down (having filled wIth gasoline vapor when purge was closed) Yet, It does not move past 2.7% when purge is closed, and does not go to zero when purge opens, it is mostly reading 2.7% or something close to it. It would seem the canister is plugged. I should test the canister on a bench somehow..

Meanwhile, there isn't a code thrown or pending, and no MIL, but the monitor for evap refuses to ready. Failing emissions as a result. I replaced the gas cap and a vacuum test pump and it's seal so far.

I'm still working on it. I'm so past buying parts and replacing them.. I'm trying to troubleshoot properly and maybe learn a few things.

Anyway , this is such a great thread. Thanks for putting in that time!


Above is a pic of my gauge set up to test evap system.
EVAP Pa - shows evap vacuum in Pa
Vacuum_Hg - I think this is intake vacuum, when purge opens this vacuum drops.
EVAP_Duty - purge valve pecentage open, when open pulls evap_vp into vacuum
EVAP_LEVEL - This is the canister charge, but it does not go past 2.7% while I'm driving.. and does not drop when the purge valve opens as indicated by EVAP_Duty.

I'll post a video on YouTube of what's happening when I'm driving and linknit here. Maybe someone can help see something I don't.

F150Torqued

@mellowmaximo I notice you are working on your 'car' and so I may not be able to be much help if the PIDs I posted in this thread do not work. (I have learned WELL that many PIDs beyond government mandated ones for major emission stuff are very 'helter-skelter' between vehicles, even of like manufacturer - AND - model).

It looks like you are on the right track though. If you have no MIL or code, I would bet you are just missing one or the other crucial conditions necessary for the Evap System to complete its monitor test. I believe you need to find/monitor some of the other signals to "FORCE" the Evap Monitor to complete. ie: EVAPSOAK - gets reset at the conclusion of each drive cycle. If you stop for coffee / donuts on the way to work - you'll NEVER get through a successful test. If you live in Uma Arizona and the "Intake Air Temp" is never below 90º - or Alaska and never above ~40º, It'll never happen. And it will only run when fuel tank level is between 15% and 75% - and at steady 'non-slosh' cruise speed above 40 mph. These conditions occur infrequently unless consciously set up. My driving habits completes one only about once for each 50 to 75 drive cycles.

I am unfamiliar with EVAP_LEVEL or canister charge?? You might provide the PID number and some 'raw' Torque data (without formula applied) under different conditions to get an idea of its meaning. But my understanding is that the Purge Valve (actually an Electronic Vapor Management Valve) is 'modulated' open very gradually via duty cycle pulses (from 0-100%). The PCM watches for first decline in tank vacuum from intake manifold vacuum -- where it knows and remembers exactly what Duty Cycle it takes for a calibrated amount of air to pass the valve. With the Normally OPEN canister vent valve relaxed (OPEN), the only restriction is air passing through the carbon canister. If it is hydrocarbon laden - less air passes through it and the system will keep the Purge Valve active for greater percentage of time to draw fuel vapors OUT of the carbon. The EVAP MODE signal is imparative to see this happening. The PCM 'constantly' manipulates the Purge valve doing this.

When conditions are proper (EVAP SOAK, Speed, IAT, Fuel Level), The Canister Vent valve is snapped closed, and the Purge valve is modulated wide OPEN (~ near 100%) to pull full intake vacuum in the fuel tank. It monitors the vacuum decay rate to determine if there is a .020 or .040 leak in the system. Of course, if it can't pull ANY vacuum (and fuel level is NOT increasing ie: re-fueling), then the Gas Cap is OFF. That gives a specific dash indication and not a DTC.

Hope this helps you sort it out on your car.

EDIT: BTW, it occurs to me that some folks have 'shot themselves in the foot' by routinely over filling their tank - (multiple clicks of the fuel nozzel). That tends to get excess liquid fuel in the vent line and carbon canister. The system needs to clear excess hydrocarbons out of the canister before it can complete full leak test.

mellowmaximo

Thanks so much for popping back into your thread for a chat. There's so much good info in your post. I'm wrapping my head around it slowly.

Here's a link to what the live data looks like with my fumbling narration. I'm still trying to get a grip on this.. word of warning it's 8 minutes long! Background: I am failing NY State emissions test because two monitors are failing to "ready " and are showing incomplete : EGR monitor, and EVAP monitor. There are NO codes pending or stored, and no service engine light on. I've changed the gas cap, and the vacuum check pump on the charcoal canister. Interesting thing is that this engine does not have an EGR valve so it's tough for me to guess what the EGR monitor is monitoring... Also, I've been intentionally underfilling gas tank to not have the test wait until the gasoline volume reaches test parameter.. Thanks again for responding. I SHALL GET TO THE BOTTOM OF THIS.

mellowmaximo

PID Canister Charge - when I set up a dial for it, the dial title Torque assigns to it automatically is EVAP Level. The charcoal canister this car has, has a vacuum test "pump" attached, which is normally OPEN, and closes when energized. This pump I assume is used to test system leaks: as you said PCM closes it while pulling vacuum, then measures vacuum decay. The PID for canister charge is not editable, so I can't see the details in Torque as to what it does.