Hummer H2. Manual - part 1660

3

DTC.  

2. Turn OFF the ignition for 30 seconds.  

3. Turn ON the ignition, with the engine OFF.  

4. Operate the vehicle within the Conditions for 

Running the DTC. You may also operate the vehicle 
within the conditions that you observed from the 
Freeze Frame/Failure Records.  

Did the DTC fail this ignition?

Go to Step 4

Go to Intermittent 

Conditions

4

1. Turn OFF the ignition.  

2. Disconnect the EVAP canister purge solenoid valve 

harness connector.  

3. Turn ON the ignition, with the engine OFF.  

4. Probe the ignition 1 voltage circuit of the EVAP 

canister purge solenoid valve with a test lamp that is 
connected to a good ground.  

Does the test lamp illuminate?

Go to Step 5

Go to Step 11

5

1. Connect a test lamp between the control circuit of 

the EVAP canister purge solenoid valve and the 
ignition 1 voltage circuit of the EVAP canister purge 
solenoid valve.  

2. Command the EVAP canister purge solenoid valve 

to 0 percent with a scan tool.  

Does the test lamp illuminate?

Go to Step 8

Go to Step 6

6

Command the EVAP canister purge solenoid valve to 50 
percent with a scan tool. 
Does the test lamp illuminate or pulse when the EVAP 
canister purge solenoid valve is commanded to 50 percent?

Go to Step 9

Go to Step 7

7

Test the control circuit of the EVAP canister purge 
solenoid valve for an open or for a short to voltage. Refer 
to Circuit Testing and Wiring Repairs in Wiring 
Systems. 
Did you find and correct the condition?

Go to Step 14

Go to Step 10

8

Test the control circuit of the EVAP canister purge 
solenoid valve for a short to ground. Refer to Circuit 
Testing and Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

Go to Step 14

Go to Step 13

9

Inspect for poor connections at the harness connector of 
the EVAP canister purge solenoid valve. 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 14

Go to Step 12

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and 

6.0L - Hummer H2

  

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 
purge 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. 

DTC P0446 

10

Inspect for poor connections at the harness connector of 
the control module. 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 14

Go to Step 13

11

Repair the open or short to ground in the ignition 1 voltage 
circuit. Refer to Wiring Repairs in Wiring Systems. 
Did you complete the repair?

Go to Step 14

-

12

Replace the EVAP canister purge solenoid valve. Refer to 
Evaporative Emission (EVAP) Canister Purge Solenoid 
Valve Replacement . 
Did you complete the replacement?

Go to Step 14

-

13

Replace the powertrain control module (PCM). Refer to 
Powertrain Control Module (PCM) Replacement . 
Did you complete the replacement?

Go to Step 14

-

14

1. Observe the Freeze Frame/Failure Records for this 

DTC.  

2. Turn OFF the ignition for 30 seconds.  

3. Turn ON the ignition, with the engine OFF.  

4. Operate the vehicle within the Conditions for 

Running the DTC. You may also operate the vehicle 
within the conditions that you observed from the 
Freeze Frame/Failure Records.  

Did the DTC fail this ignition?

Go to Step 2

Go to Step 15

15

Observe the Capture Info with a scan tool. 
Are there any DTCs that have not been diagnosed?

Go to Diagnostic 

Trouble Code 

(DTC) List

System OK

Control Module 

EVAP Canister Purge Solenoid 

EVAP Canister Vent Solenoid 

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and 

6.0L - Hummer H2

  

Conditions for Running the DTC 

z

DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, 
P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0151, P0152, P0153, 
P0154, P0155, P0156, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0449, P0452, P0453, 
P0455, P0502, P0503, P1111, P1112, P1114, P1115, P1121, P1122, P1125, P2135 are not set.  

z

The ignition voltage is between 10-18 volts.  

z

The barometric pressure (BARO) is more than 75 kPa.  

z

The fuel level is between 15-85 percent.  

z

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

z

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

z

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

Conditions for Setting the DTC 

z

The fuel tank pressure sensor is less than - 10 inches H2O.  

z

The above condition is present for more than 30 seconds.  

Action Taken When the DTC Sets 

z

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition 
cycle that the diagnostic runs and fails.  

z

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 

z

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles 
that the diagnostic runs and does not fail.  

z

A current DTC, Last Test Failed, clears when the diagnostic runs and passes.  

z

A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other 
emission related diagnostic.  

z

Clear the MIL and the DTC with a scan tool.  

Diagnostic Aids 

z

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

Command

Valve

Valve

ON

Open

Closed

OFF

Closed

Open

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and 

6.0L - Hummer H2

  

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.  

z

For intermittent conditions, refer to Intermittent Conditions .  

z

An EVAP canister, vent hose or vent solenoid valve that has restricted flow may cause this DTC to set. 
Using 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.  

DTC P0446 

Step 
or

Action

Values

Yes

No

Schematic Reference:Evaporative Emissions (EVAP) 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: 

z

A damaged EVAP canister vent solenoid 
valve - Refer to Evaporative Emission 
(EVAP) Canister Vent Solenoid Valve 
Replacement .  

z

A pinched EVAP vent hose  

z

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

1. Turn OFF the ignition.  

2. Disconnect the purge line from the EVAP 

canister purge solenoid valve. Refer to 
Evaporative Emission (EVAP) 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

IMPORTANT:

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

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0171/P0174 To DTC P0507 (TAC)) - 4.8L, 5.3L, and 

6.0L - Hummer H2