Hummer H2. Manual - part 1666

DTC P0506 (TAC) 

2

with a scan tool.  

3. Increase the engine idle to 1,200-1,500 

RPM.  

4. Observe the fuel tank pressure sensor in 

H2O with a scan tool.  

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

-1 to +1 

in H2O

Go to Intermittent 

Conditions

Go to Step 3

3

1. Turn OFF the ignition.  

2. Disconnect the EVAP purge pipe from 

the EVAP purge solenoid valve.  

3. Turn ON the ignition, with the engine 

OFF.  

4. Observe the fuel tank pressure sensor in 

H2O with a scan tool.  

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

-1 to +1 

in H2O

Go to Step 4

Go to Step 5

4

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

-

Go to Step 6

-

5

Replace the fuel tank pressure (FTP) sensor. 
Refer to Fuel Tank Pressure Sensor 
Replacement . 
Did you complete the replacement?

-

Go to Step 6

-

6

1. Connect all EVAP hardware that was 

previously disconnected.  

2. Seal the EVAP system using the 

Purge/Seal function with a scan tool.  

3. Start the engine and idle at 1,200-1,500 

RPM.  

4. Observe the fuel tank pressure sensor 

parameter with a scan tool.  

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

-1 to +1 

in H2O

Go to Step 7

Go to Step 2

7

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

 

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

  

Circuit Description 

The electronic throttle control (ETC) system uses various inputs from the powertrain control module (PCM). 
This system uses the inputs to control the idle speed through serial data circuits to the throttle actuator control 
(TAC) module. The DC motor, which is located on the throttle body, activates the throttle plate. In order to 
decrease idle speed, the TAC module commands the throttle closed, reducing air flow into the engine, and the 
idle speed decreases. In order to increase the idle speed, the TAC module commands the throttle plate open, 
allowing more air in order to bypass the throttle plate. If the actual idle RPM does not match the desired idle 
RPM within a calibrated time, this DTC will set. 

Conditions for Running the DTC 

z

DTCs P0101-P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0171, P0172, P0174, P0175, 
P0200, P0300, P0440, P0442, P0443, P0500, P0502, P0503, P1120, P1220, P1221, P1441 are not set.  

z

The engine is running for greater than 60 seconds.  

z

The engine coolant temperature (ECT) is greater than 60°C (140°F).  

z

The intake air temperature (IAT) is greater than -10°C (+14°F).  

z

The barometric pressure (BARO) is greater than 65 kPa.  

z

The system voltage is between 9-18 volts.  

z

The vehicle speed is less than 1.7 km/h (1 mph).  

z

The accelerator pedal position (APP) sensor is at 0 percent.  

Conditions for Setting the DTC 

z

The actual idle speed is 100 RPM less than the desired idle speed.  

z

The above condition is present for 5 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.  

 

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

  

z

Clear the MIL and the DTC with a scan tool.  

Test Description 

The numbers below refer to the step numbers on the diagnostic table. 

2: This test determines if the engine can achieve the commanded RPM.  

DTC P0506 (TAC) 

Step

Action

Yes

No

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

1

Did you perform the Diagnostic System Check - Engine 
Controls?

Go to Step 2

Go to Diagnostic 

System Check - 

Engine Controls

2

1. Set the park brake and block the drive wheels.  

2. Start the engine.  

3. Turn OFF all accessories.  

4. Command the engine RPM to 1,500 RPM, to 500 

RPM, and back to 1,500 RPM with the RPM control 
function of the scan tool.  

5. Exit the RPM Control function.  

Did the engine speed stay within 100 RPM of the 
commanded RPM during the above test?

Go to Step 3

Go to Step 4

3

1. Observe the Freeze Frame/Failure Records for this 

DTC.  

2. Turn OFF the ignition for 30 seconds.  

3. Use the following information to operate the vehicle 

under the conditions which set the DTC: 

z

The data in the Freeze Frame/Failure Records 

z

The parameters listed in the Conditions for 
Running in the DTC  

Does the DTC set?

Go to Step 4

Go to Intermittent 

Conditions

4

Inspect for the following conditions: 

z

Deposits in the throttle body  

z

Objects which are blocking the air intake system  

z

Energy-draining load on the engine, such as 
transmission conditions  

 

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

  

 
Did you find and correct the condition?

Go to Step 5

-

5

1. Clear the DTCs with a scan tool.  

2. Turn OFF the ignition for 30 seconds.  

3. Start the engine.  

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 6

6

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

 

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