Originally Posted by Antman3pk

I got these exact same codes with my 02 Tundra. I am assuming the diagnosing techniques would be the same. So ill be working through the process starting today.

My only question was does it mean anything different if I got a repeat of both codes? What I mean by this is the display put P0446 and P0441 twice each. I have been using the diagnosing tool for years and have never seen it pop multiple of the same code like that.

Ill be taking pictures so you will all have the opportunity to call me stupid along the way!!! (I'm actually fairly competent, I just love being sarcastic)

Originally Posted by stir_fry_boy

If you have overfilled your tank, I am told by the dealer that it takes not cents of extra gas but dollars.

Originally Posted by Mike Murrell

If the pump shuts off and you pump DOLLARS more gas, it will be all of the gas stations lot. Some systems are less susceptible than others. Depends on the evap design in my opinion.

Originally Posted by GA22RE

Okay to clarify some things here is the approach you are going to want to take on a Late-Style Intrusive System IF you had the following:

From the SET "Toyota Evaporative Emissions Systems Handbook (and some inserts for Diagnostic Help from myself):

DIAGNOSING THE LATE STYLE INTRUSIVE EVAP SYSTEM

IT IS RECOMMENDED THAT THE FIRST TIME YOU PERFORM THESE PROCEDURES, YOU DO IT ON A VEHICLE WITH NO PROBLEMS SO YOU CAN SEE WHAT IS NORMAL.


Note: If at any time during this inspection the pressure reading from the Vapor Pressure Switch fails to change, back out of that screen and go back in. You will have to start that part of the test again. There may be a momentary communication error that can be remedied this way, rather than starting unnecessary diagnosis.

TOOLS REQUIRED: Scantool, Hand Held Vacuum Pump, Vacuum "T", Pinch Pliers

1) SETUP-Go into Diagnosis, Setup, Unit Conversion and change air pressure and vapor pressure to "ABS" and "mmHG".

2) Go into Diagnosis, Enhanced OBDII, Active Test, select CAN CTRL VSV, User Data, and Select "Yes" for the VApor Pressure Sensor, now press ENTER. You should now see the Vapor Pressure Sensor reading on the scantool, and be able to turn the Canister Control VSV "ON" and "OFF".

3) The Vapor Pressure Sensor should read slightly above or below 762 mmHG.
762=Atmosphere.
IF the pressure sensor reads 762 mmHG there is probably a leak, and the system is open to atmosphere. If the pressure sensor reads above or below 762 mmHG, you know the system can hold pressure/vacuum. Now remove the gas cap. The pressure sensor should now read 762 mmHG w/ Gas Cap off. If it does not change, check the sensor for a restricted atmosphere port. (Back out of the test screen and go back in to be sure it is not an communication error w/ scantool)

4) If the sensor reads 777 mmHG, there is probably a short or open in the electrical circuit of the sensor. Check all wires to the EVAP Pressure Sensor for opens, or shorts to ground, between the ECM and the pressure sensor.

5) Put the gas cap back on and "T" in a handheld vacuum pump to the EVAP hose. This is the hose that runs from the EVAP VSV back to the canister. This is also the hose that has the green test fitting in it. ( Make sure your vacuum pump can hold a vacuum on it's own.)

6) Turn the Canister Control VSV "ON" (located on or near the air box); you should hear the VSV close. Note: The Canister Control VSV is a spring loaded open VSV. Pull 5-7" of vacuum with the pump. This should take 30-50 stokes of the vacuum pump.
-If 5-7" can be achieved in only a few strokes of the vacuum pump, check the EVAP hose and line for restrictions.
-If 5-7" of vacuum cannot be achieved, there is a large leak on the canister side of the system. Proceed with leak testing using the Miller EVAP pressure tester to find the source of the leak.
-If 5-7" of vacuum can be achieved, but gradually goes away, there is a small leak in the canister side of the system. Proceed with leak testing using the Miller EVAP system pressure tester to find the source of the leak.
Remember, creative use of the pinch-off pliers can help to narrow down the exact location of a leak. For example. if you cannot pull 5-7" of vacuum, pinch off the hose that runs from the canister to the CCV. If the leak is gone, you know it is in that hose. If the leak is still there, pinch off the hose between the canister and the vacuum pump. If the leak is now gone, you know it is in the canister itself. At this time you are only checking the purge lines, canister, and fresh air lines for leaks. You should NOT see pressure, as read by the Vapor Pressure Sensor, drop in the tank. If the pressure reading on the pressure sensor is dropping, the Bypass VSV or ORVR Valve is not sealing, allowing vacuum to get through to the tank. Thy Bypass VSV is spring-loaded closed. Remember when pressure testing with the Miller pressure tester, you are not pressurizing the fresh air lines to the canister, therefore you are not checking them for leaks. This includes the Canister Control VSV and all lines/hoses back to the canister.

7) After a couple of minutes with vacuum applied to the canister, turn the Canister Control VSV "OFF". Vacuum should drop to zero on the vacuum pump within 5-10 seconds or less. If it does not, check the fresh air lines/hoses from the Canister Control VSV back to the canister for restrictions. Also, check the Canister Control VSV operation. If no restrictions are found, there may be a faulty air inlet valve in the canister.

Note: While testing with vacuum, remember since the fuel will be warm, it will be expanding. There will be slight pressure increases on the scantool. (Slight increase means 1-2 mmHG in 10-30 seconds)

CHECKING BYPASS VSV, CANISTER AND TANK FOR OPERATION AND LEAKS

8) Go back to the active test menu and select the Tank Bypass VSV. Select your Vapor Pressure Sensor again in user data, now you can control the Bypass VSV and see the Vapor Pressure Sensor. Use pinch pliers to close the hose that goes from the Canister Control VSV to the canister. (This is the VSV that is mounted to the air filter housing.) Leave the Bypass VSV OFF. Pull 5-7" of vacuum again on the canister side of the system. Again, the vapor pressure sensor reading should not drop, this means the Bypass VSV is sealing. Note the vapor pressure sensor reading on the scantool and turn the Bypass VSV "ON". The vapor pressure sensor should immediately drop, this means the Bypass VSV is open and must be working. If pressure does not drop check that the Bypass VSV is working electrically and mechanically. (Be sure it is not a scantool communication problem as mentioned at the beginning of these procedures.)

9) With the Bypass VSV still open, continue operating the vacuum pump and watch the vapor pressure sensor readings drop. You are now pulling a vacuum on the entire EVAP system, just as the ECM does when it does it's self-check. The pressure will drop to 732-738 mmHG; this is the lowest pressure reading possible before the secondary vent activates. If vacuum cannot be achieved, or pressure rises quickly after you stop operating the vacuum pump, use the Miller tester to leak check the fuel tank side of the system for leaks. Repair any leaks found and retest.

10) The tank should hold this low pressure for several minutes. Remember, if the fuel is warm there will be a slight pressure increase as the fuel expands. If the system holds the vacuum you now know there are no leaks in the tank side, or the canister side of the system. (You are doing the exact same thing the ECM does when it checks the system for leaks.)

11) Look at the vapor pressure sensor reading while you remove the pinch-off pliers from the hose at the Canister Control VSV. (Make sure the hose does not stick shut after pliers are removed.) Atmosphere will enter through the Canister Control VSV, travel into the canister, through the Bypass VSV, on to the top of the fuel tank., through the rollover valve and into the fuel tank. If pressure does not increase to 755-758 mmHG within 10-30 seconds, check all the items mentioned above for restrictions.

12) Go back to the active test menu and select the EVAP VSV (ALONE).
Now start the engine. With the EVAP VSV OFF, there should be no vacuum applied to your vacuum gauge and no needle fluctuations. If there is, check the EVAP VSV for debris or reversed hoses. ( The engines vacuum hose always goes to the nipple furthest away from the electrical connector.) With the engine still running, turn the EVAP VSV ON. The vacuum gauge should fluctuate rapidly. If it does not, check the vacuum supply and check the EVAP VSV for electrical or mechanical failure.

*NOTES*

-The purge valve is also known as the purge vsv, or EVAP VSV on the scantool. The purge valve is spring-loaded closed when "off" electrically.
-The Canister Closed Valve is also referred to as the CCV, or Canister Control VSV on the scantool. The Canister Control VSV is spring loaded open when "off" electrically. (Only operates during testing; monitoring)
-The Bypass VSV is spring-loaded closed when "off" electrically. Remember, unless this valve is on electrically, you have two seperate systems. Tank side and Canister Side. (Only Operates during testing; monitoring)
-The Vapor pressure sensor may be directly mounted to the top of the tank or may be remotely mounted depending on the model vehicle. Also, it sees tank side pressure only unless the Bypass VSV is turned on electrically then it sees the entire system.

DESCRIPTION AND OPERATION

Pressure in Tank
As the pressure in the tank builds, it will unseat the tank valve assembly, travel through the charcoal canister, and exit through the fresh air drain.

Vacuum in Tank
As pressure drops in the tank, fresh air comes through the Canister Control VSV, through the air valve, through the canister, through the vacuum check valve, and into the tank through a rollover valve.

Secondary Vacuum Release
The secondary vacuum release is the one way check valve in the gas cap.

Refueling
While refueling, high pressure in the tank forces fumes through the rollover valve, out through the On-Board Refueling Vapor Recovery Valve, through the charcoal canister, and out the fresh air valve.

Purge Mode
While purging, when the EVAP VSV is turned on, it draws air in through the Canister Closed Valve, through the air inlet valve, charcoal canister, and EVAP VSV and into the engine so the hydrocarbons stored in the canister can be burned.

EVAP MONITORS, A BRIEF EXPLANATION

The monitor is when the ECM checks the EVAP system for proper operation and leaks. Understanding how the ECM checks the system is the key to understanding the types of failures you will see on vehicles.

In order for the monitors to run the following conditions must be met:

-Cold start with coolant temp and air intake temp within 12 degrees of each other.
-Coolant temp between 50-90 degrees.
-Vehicle must be driven in stop and go conditions (LA4 drive cycle).

STAGE 1: The ECM looks for the vapor pressure to increase from it's starting point. This means that there is enough fuel in the tank and that the system is basically sound. While the ECM is is looking at the pressure rise, it is purging to make sure the EVAP VSV is working. IF pressure rises the ECM will continue on to stage 2. (Anything better than Atmospheric pressure when vehicle has sat over-night.)

STAGE 2: The ECM will open the Bypass VSV, this connects the tank directly through to the canister. Then the ECM closes the Canister Control VSV sealing off the fresh air line. With the EVAP VSV on, the canister and tank will go into a low-pressure condition. The ECM looks at the vapor pressure sensor to see if this low pressure can be achieved, if it can, the ECM continues with stage 3.
(If utilizing the scantool and manually performing a EVAP cycle you will more than likely want to see pressure's go from around 762 to 765 then sink to around 740 mmHG.)

STAGE 3: Stage 3 is the actual leak check part of the monitor. If a vacuum could be achieved (no huge leaks) the ECM looks to see how quickly the pressure increases to determine how large the leak is. A very quick increase is a large leak, very slow leak a small leak, a very, very, slow increase is acceptable. After the leak check, the ECM continues on with stage 4.
(If utilizing the scantool and manually performing a EVAP cycle you are not going to wan to see anything above the threshold. Usually anything above .40 thousandths of an increase will produce a P0442 or a P0445.)

STAGE 4: Stage 4 is where the ECM checks the CCV operation and the fresh air lines for restrictions. It is looking for pressure in the tank to quickly increase when the CCV is turned off, (opened mechanically).

STAGE 5: Stage 5 is the final stage and is when the ECM checks the operation of the Bypass VSV. Before tank pressure reaches atmosphere, the ECM turns the Bypass VSV off, making it close. If the Bypass VSV is working properly, the pressure should stop rising so quickly now that the tank is once again isolated from the canister.

*NOTE*

Here's a little rule of to remember the next time one of these DTC's presents itself:

-During Stage 2 the following codes can be stored by the ECM: P0441 (Incorrect Purge Flow)
-During Stage 3 the following codes can be stored by the ECM: P0440 (EVAP Control System Malfunction), P0442 (Small leak detected), P0456 (Very small leak detected)
-During Stage 5 the following codes can be stored by the ECM: P0446 (EVAP Vent Control System Malfunction)
P.S. don't forget about P0455 (Gross leak detected)