P0446 Evap Code

[bluebear15]

I recently got the check engine light on my 06 Tahoe Z71 and I scanned it and got the P0446 evap system code. A few months ago I replaced the evap canister and purge valve for having the same code since I was also experiencing where the pump would click off a bunch of times while trying to fill the tank. This time I am smelling fuel fumes from the back by the gas cap area. Wasn't sure if there was more to check for and if there is what to check.

 

[915_Tahoe]

HAVE YOU CHANGE OUT THE GAS CAP, IF NOT I WOULD RECOMMEND THAT CHEAP AND EASY TO DO. MAKE SURE YOU GET AN OEM CAP NOT AFTERMARKET, THOSE DON'T SEAL AS WELL. YOU WILL HAVE TO PUT MILES ON THE TRUCK SO THE CEL CAN TURN OFF.

 

[bluebear15]

HAVE YOU CHANGE OUT THE GAS CAP, IF NOT I WOULD RECOMMEND THAT CHEAP AND EASY TO DO. MAKE SURE YOU GET AN OEM CAP NOT AFTERMARKET, THOSE DON'T SEAL AS WELL. YOU WILL HAVE TO PUT MILES ON THE TRUCK SO THE CEL CAN TURN OFF.

No haven’t replaced the gas cap yet

 

[915_Tahoe]

this is what i pulled up, let see if it helps

#04-06-04-055A: LR4, LM4, LM7, L59, LQ9, LQ4, L18 DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket) - (Mar 20, 2006)
Subject: LR4, LM4, LM7, L59, LQ9, LQ4, L18 DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Vent Solenoid and Bracket)

Models: 2000–2003 Cadillac Escalade
2002–2003 Cadillac Escalade EXT
2003 Cadillac Escalade ESV
2000–2003 Chevrolet Suburban, Tahoe
2002–2003 Chevrolet Avalanche
2000– 2003 GMC Yukon, Yukon XL
with 4.8L, 5.3L, 6.0L, 8.1L Vortec™ V8 Engine (VINs V, P, T, Z, N, U, G — RPOs LR4, LM4, LM7, L59, LQ9, LQ4, L18)

This bulletin is being revised to add updated warranty information and enhance the content. Please discard Corporate Bulletin Number 04-06-04-055 (Section 06 — Engine/Propulsion System).

Condition
Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.

Cause
Dirt and dust intrusion into the EVAP canister vent solenoid, resulting in restricted air flow, may cause this condition.

Correction
DO THIS
Replace the EVAP vent solenoid with a more robust vent solenoid.

DON'T DO THIS
DO NOT Replace the EVAP canister or other EVAP parts.

After following the Service Manual diagnostic P0446 and determining that the EVAP canister vent valve is the cause of the SES light, replace the existing EVAP canister vent solenoid and bracket. This new vent solenoid has an enhanced filtering capability and a filter element that can be easily removed and cleaned. To ensure correct installation, follow the procedure below.

1. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the bolt retaining the vent valve bracket.
3. Disconnect the electrical connector.
4. Disconnect the canister vent valve hose.
5. Install the new vent valve bracket, P/N 15105605, to the vehicle with the retaining bolt.
   Tighten
   Tighten the bracket mounting bolt to 12 Y (106 lb in).
6. Install the new vent valve, P/N 10382105, to the bracket.
7. Reinstall the electrical connector.
8. Reinstall the canister vent valve hose.
9. Lower the vehicle.
10. Clear the DTC.

Parts Information

Description
qty 1.
15105605
Bracket, EVAP Emission Canister Purge

qty 1.
10382105
Valve, EVAP Emission Canister Control

 

[OneofFew]

You may not have used the one with the updated design. Ive see the old style still for sale.

 

[915_Tahoe]

You may not have used the one with the updated design. Ive see the old style still for sale.

HERE AT THE DEALER WILL ONLY HAVE THE UPDATED PART, YOU COULD MAYBE FIND IT AFTERMARKET IN THE OLD DESIGN.

 

[Doubeleive]

Did you change the 2nd solenoid on the intake also?

 

[bluebear15]

Did you change the 2nd solenoid on the intake also?

I changed the evap canister on the back of the fuel tank and the purge solenoid on the intake. I’m assuming that’s the one you’re referring to.

Do they still sell the non updated one at Advance Auto? I got the AC Delco ones.

The one thing that is leading me to maybe a leak is the strong smell of fuel fumes both by the engine bay and the back by the gas cap/filler neck. Just weird that it would happen a month or so after I changed the Evan canister and purge solenoid.

 

[915_Tahoe]

I say do the gas cap, might fix the issue. There like 20-30$.

 

[Doubeleive]

I changed the evap canister on the back of the fuel tank and the purge solenoid on the intake. I’m assuming that’s the one you’re referring to.

Do they still sell the non updated one at Advance Auto? I got the AC Delco ones.

The one thing that is leading me to maybe a leak is the strong smell of fuel fumes both by the engine bay and the back by the gas cap/filler neck. Just weird that it would happen a month or so after I changed the Evan canister and purge solenoid.

I don't know when I did mine I went with the "standard" brand I think is what it was called ordered from rock auto

 

[bluebear15]

Was looking at it some more tonight and noticed there’s fuel leaking from the top of the gas tank in the back. I’m guessing it’s coming out by the fuel pump assembly. Wasn’t sure if it’s actually leaking or if it’s leaking due to the pressure caused by the evaporated canister or purge valve

 

[Rocket Man]

Probably rusted fittings at the fuel pump, a known issue especially in the rust belt. Evap problem should not cause a fuel leak. Looks like it’s time to drop the tank.

 

[bluebear15]

Probably rusted fittings at the fuel pump, a known issue especially in the rust belt. Evap problem should not cause a fuel leak. Looks like it’s time to drop the tank.

Thanks! I’m planning on dropping the tank and doing the fuel pump along with the sending unit. The evap code went away so I’m wondering if it’s only when the tank is full

 

[Chubbs]

There are 2 EVAP solenoids. (1) on the engine "purge solenoid" and a different "EVAP vent valve/solenoid" back behind the gas tank hanging by itself. That 2nd gets stuck open or closed and it perpetrates the same symptoms as a faulty purge valve.

EVAP Purge Solenoid
The EVAP purge solenoid controls the flow of vapors from the EVAP system to the intake manifold. The purge solenoid opens when commanded ON by the control module. This normally closed solenoid is pulse width modulated (PWM) by the control module to precisely control the flow of fuel vapor to the engine. The solenoid will also be opened during some portions of the EVAP testing, allowing engine vacuum to enter the EVAP system.

EVAP Vent Solenoid
The EVAP vent solenoid controls fresh airflow into the EVAP canister. The solenoid is normally open. The control module commands the solenoid ON, closing the solenoid during some EVAP tests, allowing the system to be tested for leaks.


Chassis Mounted Fuel/EVAP Controls– 10 Series

Click to Enlarge
1 Fuel Pump and Sender Assembly

2 Evaporative Emissions (EVAP) Canister Vent Solenoid

 

[Chubbs]

DTC P0446
DTC P0446
System Description
This DTC tests the evaporative emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid Open and the EVAP canister vent solenoid Closed. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid Closed and the EVAP canister vent solenoid Open. The control module monitors the fuel tank pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 inches H2O in a calibrated time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent valves.


Control Module Command EVAP Canister Purge Solenoid EVAP Canister Vent Solenoid
ON


Open


Closed


OFF


Closed


Open


Conditions for Running the DTC

• DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, P1120 are not set.
  
  
• The ignition voltage is between 10–18 volts.
  
  
• The barometric pressure (BARO) is more than 75 kPa.
  
  
• The fuel level is between 15–85 percent.
  
  
• The startup engine coolant temperature (ECT) is between 4–30°C (39–86°F).
  
  
• The startup intake air temperature (IAT) is between 4–30°C (39–86°F).
  
  
• The startup ECT and IAT are within 9°C (16°F) of each other.
  

Conditions for Setting the DTC

• The fuel tank pressure sensor is less than −10 inches H2O.
  
  
• The above condition is present for more than 30 seconds.
  

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
  
  
• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
  

Conditions for Clearing the MIL/DTC

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  
  
• A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  
  
• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  
  
• Clear the MIL and the DTC with a scan tool.
  

Diagnostic Aids

• An intermittent condition could be caused by a damaged evaporative emission (EVAP) vent housing, a temporary blockage at the EVAP vent solenoid inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem.
  
  
• For intermittent conditions, refer to Intermittent Conditions
  

Test Description
The number below refers to the step number on the diagnostic table.

1. This test determines if the failure is present or intermittent.
   

DTC P0446


Step




Action


Values


Yes


No


Schematic Reference: Emission Hose Routing Diagram


1


Did you perform the Diagnostic System Check–Engine Controls?


—


Go to Step 2


Go to Diagnostic System Check - Engine Controls


2


Inspect the evaporative emission (EVAP) system for the following conditions:

• A damaged EVAP vent solenoid—Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement.
  
  
• A pinched EVAP vent hose
  
  
• A damaged EVAP canister—Refer to Evaporative Emission Canister Replacement (1500 Series) | Evaporative Emission Canister Replacement (2500 Series).
  

Did you find and correct the condition?


—


Go to Step 15


Go to Step 3


3

1. Turn OFF the ignition.
   
   
2. Disconnect the purge line from the EVAP purge solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement.
   
   
3. Turn ON the ignition, with the engine OFF.
   

Is the fuel tank pressure sensor parameter within the specified range?


-1 to +1 in H2O


Go to Step 4


Go to Step 9


4

1. Turn OFF the ignition.
   
   
2. Connect the EVAP purge pipe.
   
   
3. Connect the J 41413-200 | J 41413-200 Evaporative Emissions System Tester (EEST) power supply clips to a known good 12-volt source.
   
   
4. Install the J 41415-40 | J 41415-40 Fuel Tank Cap Adapter to the fuel fill pipe.
   
   
5. Connect the fuel fill cap to the J 41415-40 | J 41415-40.
   
   
6. Connect the J 41413-200 | J 41413-200nitrogen/smoke supply hose to the J 41415-40 | J 41415-40.
   
   
7. Turn ON the ignition, with the engine OFF
   
   
8. Command the EVAP vent solenoid closed with a scan tool.
   
   
9. Turn the nitrogen/smoke valve on the J 41413-200 | J 41413-200 control panel to NITROGEN.
   
   
10. Use the remote switch to pressurize the EVAP system to the first specified value.
    
    
11. Observe the fuel tank pressure sensor in H2O with a scan tool.
    
    
12. Command the EVAP vent solenoid open with a scan tool.
    

Is the fuel tank pressure sensor parameter less than the second specified value?


5 in H2O

1 in H2O


Go to Step 5


Go to Step 7


5

1. Connect the nitrogen/smoke hose to the EVAP service port.
   
   
2. Remove the J 41415-40 | J 41415-40.
   
   
3. Install the fuel fill cap to the fuel fill pipe.
   
   
4. Start the engine.
   
   
5. Allow the engine to idle.
   
   
6. Use the purge/seal function to seal the system, with a scan tool.
   
   
7. Command the EVAP canister purge solenoid valve to 30 percent.
   
   
8. Observe the vacuum/pressure gauge of the J 41413-200 | J 41413-200 until it reaches approximately 16 in H2O.
   
   
9. Use the purge/seal function to seal the system, with a scan tool.
   

Is the FTP parameter on a scan tool within the specified value of the vacuum/pressure gauge on the J 41413-200 | J 41413-200 , until the vacuum reached the abort limit on a scan tool?


1 in H2O


Go to Step 6


Go to Step 9


6


Did the FTP parameter on a scan tool display more than the specified value?


3.2 V


Go to Diagnostic Aids


Go to Step 9


7


Disconnect the EVAP vent hose from the EVAP vent solenoid.

Is the fuel tank pressure sensor parameter less than the specified value?


1 in H2O


Go to Step 13


Go to Step 8


8


Disconnect the EVAP vent hose from the EVAP canister.

Is the fuel tank pressure sensor parameter less than the specified value?


1 in H2O


Go to Step 11


Go to Step 14


9


Test the low reference circuit of the FTP sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?


—


Go to Step 15


Go to Step 10


10


Test for poor connections at the harness connector of the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?


—


Go to Step 15


Go to Step 12


11


Repair the pinched or restricted EVAP vent hose.

Did you complete the repair?


—


Go to Step 15


—


12


Replace the FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement (Front Tank (1500 Series Only)) | Fuel Tank Pressure Sensor Replacement (Rear Tank).

Did you complete the replacement?


—


Go to Step 15


—


13


Replace the EVAP vent solenoid. Refer to Evaporative Emission Canister Vent Solenoid Valve Replacement.

Did you complete the replacement?


—


Go to Step 15


—


14


Replace the EVAP canister. Refer to Evaporative Emission Canister Replacement (1500 Series) | Evaporative Emission Canister Replacement (2500 Series).

Did you complete the replacement?


—


Go to Step 15


—


15

1. Turn OFF the ignition.
   
   
2. Disconnect the purge line from the EVAP purge solenoid. Refer to Evaporative Emission Canister Purge Solenoid Valve Replacement.
   
   
3. Turn ON the ignition, with the engine OFF.
   

Is the fuel tank pressure sensor parameter within the specified range?


-1 to + 1 in H2O


Go to Step 16


Go to Step 2


16

1. Turn OFF the ignition.
   
   
2. Reconnect all disconnected components.
   
   
3. Connect the J 41413-200 | J 41413-200 to the fuel fill pipe.
   
   
4. Turn ON the ignition, with the engine OFF
   
   
5. Command the EVAP vent solenoid closed with a scan tool.
   
   
6. Turn the nitrogen/smoke valve on the J 41413-200 | J 41413-200 control panel to NITROGEN.
   
   
7. Use the remote switch to pressurize the EVAP system to the first specified value.
   
   
8. Observe the fuel tank pressure sensor in H2O with a scan tool.
   
   
9. Command the EVAP vent solenoid open with a scan tool.
   

Is the fuel tank pressure sensor parameter less than the second specified value?


5 in H2O

1 in H2O


Go to Step 17


Go to Step 2


17


Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

 

[Doubeleive]

easier to just replace it and call it a day

 

[bluebear15]

Thanks everyone for all the info. Turned out to be the rusted fuel line on top of the sending unit for the fuel pump was leaking. That was causing whatever other stuff to misread and give the code. Replaced the fuel pump this past weekend and no more code