Hummer H2. Manual - part 1662

6: This step tests if the EVAP canister vent solenoid valve control circuit is grounded.

DTC P0449

Step

Action

Yes

Schematic Reference:Engine Controls Schematics
Connector End View Reference:Engine Controls Connector End Views or Powertrain Control
Module (PCM) Connector End Views

Did you perform the Diagnostic System Check - Engine
Controls?

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

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

2. Command the evaporative emission (EVAP) canister

vent solenoid valve ON and OFF with the scan tool.

Do you hear or feel a click from the EVAP canister vent
solenoid valve when the valve is commanded ON and OFF?

Go to Step 3

Go to Step 4

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 4

Go to Intermittent

Conditions

1. Turn OFF the ignition.

2. Disconnect the EVAP canister vent solenoid valve.

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

4. Probe the batter positive voltage circuit of the EVAP

canister vent solenoid valve with a test lamp
connected to a good ground. Refer to
Troubleshooting with a Test Lamp in Wiring
Systems.

Does the test lamp illuminate?

Go to Step 5

Go to Step 11

1. Connect a test lamp between the control circuit of the

EVAP canister vent solenoid valve and battery
positive voltage circuit of the EVAP canister vent
solenoid valve at the EVAP canister vent solenoid
valve harness connector.

2. Command the EVAP canister vent solenoid valve ON

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

and OFF with a scan tool.

Does the test lamp turn ON and OFF with each command?

Go to Step 9

Go to Step 6

Does the test lamp remain illuminated with each command?

Go to Step 8

Go to Step 7

Test the control circuit of the EVAP canister vent solenoid
valve for a short to voltage or an open. 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

Test the control circuit of the EVAP canister vent 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 10

Inspect for poor connections at the harness connector of the
EVAP canister vent solenoid valve. Refer to Testing for
Intermittent Conditions and Poor Connections and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step 14

Go to Step 12

Inspect for poor connections at the harness connector of the
control module. Refer to Testing for Intermittent
Conditions and Poor Connections and Wiring Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to Step 14

Go to Step 13

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

IMPORTANT:

If the fuse is open, inspect all related circuits for a short
to ground.

Go to Step 14

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 14

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

Go to Step 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.

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 P0452

Circuit Description

The fuel tank pressure (FTP) sensor measures the difference between the air pressure or vacuum in the
evaporative emission (EVAP) system, and the outside air pressure. The control module supplies a 5-volt
reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending
on EVAP system pressure or vacuum. If the FTP sensor signal voltage goes below a calibrated value, this DTC
sets.

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system
pressure/vacuum.

DTC P0452

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The fuel tank pressure (FTP) sensor voltage is less than 0.1 volts.

All conditions are 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

Did the DTC fail this ignition?

Go to Step 2

Go to Step 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

FTP Sensor Signal Voltage

Fuel Tank Pressure

High, Approximately 1.5 Volts or More

Negative Pressure/Vacuum

Low, Approximately 1.5 Volts or Less

Positive Pressure

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

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.

Test Description

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

5: This step tests for the proper operation of the circuit in the high voltage range.

DTC P0452

Step

Action

Value

(s)

Yes

Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Powertrain Control
Module (PCM) Connector End Views

Did you perform the Diagnostic System Check -
Engine Controls?

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

1. Idle the engine for 1 minute.

2. Monitor the diagnostic trouble code (DTC)

information with a scan tool.

Did DTC P0641 or P0651 fail this ignition?

Go to

Diagnostic

Trouble Code

(DTC) List

Go to Step 3

Observe the fuel tank pressure sensor parameter with
the scan tool.
Does the scan tool indicate that fuel tank pressure
sensor parameter is less than the specified value?

0.1 V

Go to Step 5

Go to Step 4

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 5

Go to Intermittent

Conditions

1. Turn OFF the ignition.

2. Raise and support the vehicle. Refer to Lifting

and Jacking the Vehicle in General

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

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