Evap System Problem?

Scimmia · July 9, 2007

This is for my Dad, who has a 2005 Yukon Denali with right around 100,000 mi on it

The CEL came on, I pulled a code 0446. I found the TSB posted here for earlier model trucks that says the the canister above the rear axel can become clogged with dust. I pulled it off and it was completely CRAMMED full (lot of time on gravel). We just replaced it with a new one at that point and reset the light. Unfortunately, it came back on again after a couple of days, so the next time I was up there, I pulled the line going to the canister off, figuring it was clogged, and blew air through it. Reset light, came back on again . At this point, we just let it be.

Now, a few months ago, he started complaining about the gas pump clicking off on him constantly. This was a new development. He's tried it on slow speeds, with the nozzel barily in or all the way in, everything we can think of and was still having the problem, so he took it to the dealer. They tried to blow air through an EVAP line on the top of the tank, and said that it must have collapsed. They could drop the tank and replace it.

So he took it in to get the lines replaced, and now they tell him that the problem is a limit switch in the tank, and since it's part of the tank, he'll need a whole new one! $650 plus labor! So he calls me to see what we can get a tank for from somewhere else (GMPD or elsewhere), so we could replace it ourselves. The whole limit switch story sounds kind of fishy to me, so I thought I'd check here to see if anyone knew anything about this.

Thanks for your help!

Norseman · July 9, 2007

This is for my Dad, who has a 2005 Yukon Denali with right around 100,000 mi on it

The CEL came on, I pulled a code 0446. I found the TSB posted here for earlier model trucks that says the the canister above the rear axel can become clogged with dust. I pulled it off and it was completely CRAMMED full (lot of time on gravel). We just replaced it with a new one at that point and reset the light. Unfortunately, it came back on again after a couple of days, so the next time I was up there, I pulled the line going to the canister off, figuring it was clogged, and blew air through it. Reset light, came back on again . At this point, we just let it be.

Now, a few months ago, he started complaining about the gas pump clicking off on him constantly. This was a new development. He's tried it on slow speeds, with the nozzel barily in or all the way in, everything we can think of and was still having the problem, so he took it to the dealer. They tried to blow air through an EVAP line on the top of the tank, and said that it must have collapsed. They could drop the tank and replace it.

So he took it in to get the lines replaced, and now they tell him that the problem is a limit switch in the tank, and since it's part of the tank, he'll need a whole new one! $650 plus labor! So he calls me to see what we can get a tank for from somewhere else (GMPD or elsewhere), so we could replace it ourselves. The whole limit switch story sounds kind of fishy to me, so I thought I'd check here to see if anyone knew anything about this.

Thanks for your help!

P0446 -- the problem is the purge solinoid on top of the intake manifold. Replace it. Ten minute job.

I can send you a picture of its location if you need it.

The gas pump clicking off is a whole other issue.

Schmids5.3l · July 9, 2007

I had the same code, it would come on for a day or two and go away for a week, haven't had it come on for a month or so now.

Norseman · July 9, 2007

I had the same code, it would come on for a day or two and go away for a week, haven't had it come on for a month or so now.

It's the purge solinoid.

GMTRUCKTECH · July 10, 2007

I AM GOING TO GIVE YOU THE FLOW CHART FOR THIS CODE BUT I WANT YOU TO PAY CLOSE ATTENTION TO THE DIAGANOSTIC AIDS SECTION BECAUSE YOU HAVE STATED YOU HAVE ALREADY FOUND BLOCKAGE IN A EVAP HOSE AND YOU HAVE FUEL FILL ISSUES. GOOD LUCK

Document ID# 1397757

2005 GMC Truck Yukon Denali

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 valve Open and the EVAP canister vent solenoid valve 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 valve Closed and the EVAP canister vent solenoid valve 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 solenoid valves.

Control Module Command

EVAP Canister Purge Solenoid Valve

EVAP Canister Vent Solenoid Valve

ON

Open

Closed

OFF

Closed

Open

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0446 Evaporative Emission (EVAP) Vent System Performance

Conditions for Running the DTC

• DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0502, P0503, P1111, P1112, P1114, P1115, P1121, P1122, P1125, P2135 are not set.

• The ignition voltage is between 10-18 volts.

• The barometric pressure (BARO) is greater than 75 kPa.

• The fuel level is between 15-85 percent.

• The engine coolant temperature (ECT) is between 4-30°C (39-86°F).

• The intake air temperature (IAT) is between 4-30°C (39-86°F).

• The start up ECT and IAT are within 9°C (16°F) of each other.

• DTC P0446 runs once per cold start when the above conditions are met.

Conditions for Setting the DTC

• The fuel tank pressure sensor is less than -12 inches H2O.

• The above condition is present for more than 5 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

• When using the Evaporative Emission System Tester (EEST) to apply pressure, you can regulate the amount of pressure by activating the remote switch ON and OFF while observing pressure in the EVAP system using a scan tool. DO NOT use more than 5 inches H2O. More than 5 inches H2O applied to the EVAP system can cause the canister vent solenoid valve to temporarily remain in the closed position, which could lead to misdiagnosis in this procedure.

• An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP canister vent solenoid valve 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

Testing for Intermittent Conditions and Poor Connections .

• An EVAP canister, vent hose, or vent solenoid valve that has restricted flow may cause this DTC to set. Using a purge solenoid valve command with a scan tool will allow vacuum to be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, vacuum should not increase to more than 9 inches H2O.

Step

Action

Values

Yes

No

Schematic Reference: Evaporative Emissions (EVAP) Hose Routing Diagram

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Inspect the Evaporative Emission (EVAP) System for the following conditions:

• A damaged EVAP canister vent solenoid valve--Refer to

Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .

• A pinched EVAP vent hose

• A damaged EVAP canister--Refer to

Evaporative Emission (EVAP) Canister Replacement .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 3

3

<LI type=1>Turn OFF the ignition. <LI type=1>Remove the fuel filler cap.
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

<LI type=1>Turn OFF the ignition. <LI type=1>Connect the

J 41413-200 Evaporative Emission System Tester (EEST) power supply clips to a known good 12-volt source. <LI type=1>Install the J 41415-40 Fuel Tank Cap Adapter or GE-41415-50 Fuel Tank Cap Adapter to the fuel fill pipe. <LI type=1>Connect the fuel fill cap to the J 41415-40 or to GE-41415-50 . <LI type=1>Connect the J 41413-200 nitrogen/smoke supply hose to J 41415-40 or to GE-41415-50 . <LI type=1>Turn ON the ignition, with the engine OFF. <LI type=1>Command the EVAP canister vent solenoid valve closed with a scan tool. <LI type=1>Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. Important: DO NOT exceed the specified value in this step. Exceeding the specified value may cause the EVAP canister vent solenoid valve to remain closed, or produce incorrect test results.

<LI type=1>Use the remote switch to pressurize the EVAP system to the first specified value. <LI type=1>Observe the fuel tank pressure sensor in H2O with a scan tool.
Command the EVAP canister vent solenoid valve 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

<LI type=1>Connect the

J 41413-200 nitrogen/smoke supply hose and the vehicle fuel fill cap to the J 41415-40 or GE-41415-50 . <LI type=1>Start the engine. <LI type=1>Allow the engine to idle. <LI type=1>Use the purge/seal function to seal the system with a scan tool. <LI type=1>Command the EVAP canister purge solenoid valve to 20 percent. <LI type=1>Observe the vacuum/pressure gage of the J 41413-200 and the FTP parameter on the scan tool.
Allow the vacuum to increase on the gage of the J 41413-200 until it reaches approximately 16 inches H2O.

Did the pressure reading on the J 41413-200 gage agree with the scan tool FTP parameter until the vacuum reached the abort limit on the scan tool?

--

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 12

7

Disconnect the EVAP vent hose from the EVAP canister vent solenoid valve.

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 for an intermittent and for a poor connection at the fuel tank pressure (FTP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 10

10

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

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 .

Did you complete the replacement?

--

Go to Step 15

--

13

Replace the EVAP canister vent solenoid valve. Refer to Evaporative Emission (EVAP) Canister Vent Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the EVAP canister. Refer to Evaporative Emission (EVAP) Canister Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15

<LI type=1>Turn OFF the ignition. <LI type=1>Remove the fuel filler cap.
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

Important: DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results.

<LI type=1>Turn OFF the ignition. <LI type=1>Reconnect all disconnected components. <LI type=1>Connect

J 41413-200 to the fuel fill pipe. <LI type=1>Turn ON the ignition, with the engine OFF. <LI type=1>Command the EVAP canister vent solenoid valve closed with a scan tool. <LI type=1>Turn the nitrogen/smoke valve on the J 41413-200 control panel to NITROGEN. <LI type=1>Use the remote switch to pressurize the EVAP system to the first specified value. <LI type=1>Observe the fuel tank pressure sensor in H2O with a scan tool.
Command the EVAP canister vent solenoid valve 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.

Have any other DTCs not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK

mahp2000 · April 4, 2008

This is for my Dad, who has a 2005 Yukon Denali with right around 100,000 mi on it

The CEL came on, I pulled a code 0446. I found the TSB posted here for earlier model trucks that says the the canister above the rear axel can become clogged with dust. I pulled it off and it was completely CRAMMED full (lot of time on gravel). We just replaced it with a new one at that point and reset the light. Unfortunately, it came back on again after a couple of days, so the next time I was up there, I pulled the line going to the canister off, figuring it was clogged, and blew air through it. Reset light, came back on again . At this point, we just let it be.

Now, a few months ago, he started complaining about the gas pump clicking off on him constantly. This was a new development. He's tried it on slow speeds, with the nozzel barily in or all the way in, everything we can think of and was still having the problem, so he took it to the dealer. They tried to blow air through an EVAP line on the top of the tank, and said that it must have collapsed. They could drop the tank and replace it.

So he took it in to get the lines replaced, and now they tell him that the problem is a limit switch in the tank, and since it's part of the tank, he'll need a whole new one! $650 plus labor! So he calls me to see what we can get a tank for from somewhere else (GMPD or elsewhere), so we could replace it ourselves. The whole limit switch story sounds kind of fishy to me, so I thought I'd check here to see if anyone knew anything about this.

Thanks for your help!

P0446 -- the problem is the purge solinoid on top of the intake manifold. Replace it. Ten minute job.

I can send you a picture of its location if you need it.

The gas pump clicking off is a whole other issue.

Hi there this MAHP 2000.

I have a 2005 c¿Chevrolet Silverado 2WD Crew Cab with 45,000 miles.

I got the "check engine" on and as the result of the sacanning I got two problems:

P0449 and P0454. I took the truck to the dealer and they want to dismounting the gas tank for almos 300 box. I am reading about these troubles and I don think is necessary to get involved with the gas tank.

Do you have a photo or diagram of the parts I need to check?

Thanks for your support.

Unquote