Hummer H2. Manual - part 1579

flash memory or an internal TAC module processor fault is detected, this DTC sets. 

Conditions for Running the DTC 

z

DTC U0107 is not set.  

z

The ignition switch is in the Crank or Run position.  

z

The ignition voltage is greater than 6 volts.  

Conditions for Setting the DTC 

z

The TAC module determines that an internal data test did not pass.  

z

The above condition is met for more than 1 second.  

Action Taken When the DTC Sets 

z

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. 

z

The control module records the operating conditions at the time the diagnostic fails. The control module 
stores this information in the Freeze Frame and/or the Failure Records.  

z

The control module commands the TAC system to operate in the Reduced Engine Power mode.  

z

A message center or an indicator displays Reduced Engine Power.  

z

Under certain conditions the control module commands the engine OFF.  

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

Verify that the starting and charging systems are operating properly. Low system voltage can cause this 
DTC to set.  

z

Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs 
may set without any circuit or component conditions found during diagnostic testing.  

z

When the TAC module detects a condition within the TAC system, more than one TAC system related 
DTC may set. This is due to the many redundant tests run continuously on this system. Locating and 
repairing an individual condition may correct more than one DTC. Disconnecting components during 
testing may set additional DTCs. Remember this if you review the stored information in Capture Info.  

Test Description 

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0507 (TAC) To DTC U0107) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

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

4: Locating and repairing an individual condition may correct more than one DTC.  

DTC P2108 

DTC P2120 

Circuit Description 

The accelerator pedal position (APP) sensor 1 is a potentiometer type sensor with the following three circuits: 

z

A 5-volt reference circuit  

z

A low reference circuit  

z

A signal circuit  

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP 
sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 
signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the 
APP sensor 1 signal or APP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

Step

Action

Yes

No

Schematic Reference:Engine Controls Schematics 
Connector End View Reference:Engine Controls Connector End 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

Replace the throttle actuator control (TAC) module. Refer 
to Throttle Actuator Control (TAC) Module 
Replacement . 
Did you complete the replacement?

Go to Step 3

-

3

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 4

4

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 P0507 (TAC) To DTC U0107) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

Conditions for Running the DTC 

z

DTCs P0601, P0602, P0606, P2108, U0107 are not set.  

z

The ignition switch is in the Crank or Run position.  

z

The ignition voltage is more than 5.23 volts.  

Conditions for Setting the DTC 

z

The APP sensor 1 voltage is less than 0.24 volts or more than 4.49 volts. 

OR 

z

The 5-volt reference is less than 4.54 volts or more than 5.21 volts.  

z

One of the above conditions is present for more than 1 second.  

Action Taken When the DTC Sets 

z

The control module stores the DTC information into memory when the diagnostic runs and fails.  

z

The malfunction indicator lamp (MIL) will not illuminate.  

z

The control module records the operating conditions at the time the diagnostic fails. The control module 
stores this information in the Failure Records.  

z

If one or more APP sensor DTCs are set, the following occurs: 

{

The control module commands Reduced Engine Power mode.  

{

The APP indicated angle is limited to a predetermined value to limit the amount of throttle control. 

OR 

{

The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. 

{

The message center displays Reduced Engine Power.  

Conditions for Clearing the DTC 

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 
non-emission related diagnostic.  

z

Clear the DTC with a scan tool.  

Diagnostic Aids 

z

Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water 
intrusion occurs, multiple DTCs may set without any circuit or component conditions found during 
diagnostic testing.  

z

When the TAC module detects a condition within the TAC system, more than one TAC system related 
DTC may set. This is due to the many redundant tests run continuously on this system. Locating and 

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0507 (TAC) To DTC U0107) - 4.8L, 5.3L, and 6.0L - 

Hummer H2

  

repairing one individual condition may correct more than one DTC. Disconnecting components during 
testing may set additional DTCs. Remember this if you review the stored information in Capture Info.  

z

For an intermittent, refer to Intermittent Conditions .  

Test Description 

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

12: This test isolates whether the short is to another TAC system circuit in the harness or within the TAC 
module.  

26: When the TAC module detects a condition within the TAC system, more than one TAC system 
related DTC may set. This is due to the many redundant tests run continuously on this system. Locating 
and repairing one individual condition may correct more than one DTC. Disconnecting components 
during testing may set additional DTCs. Remember this if you review the stored information in Capture 
Info.  

DTC P2120 

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics 
Connector End View Reference: Engine Controls Connector End 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. Turn ON the ignition with the engine OFF, and 

with your foot OFF the accelerator pedal.  

2. Observe the accelerator pedal position (APP) 

sensor 1 voltage with a scan tool.  

Does the scan tool indicate the APP sensor 1 voltage 
is within the specified values?

IMPORTANT:

If DTCs P0120 or U0107 is also set, refer to the 
appropriate DTC for further diagnosis.

0.24-

2.24 V

Go to Step 3

Go to Step 6

3

Depress the accelerator pedal to the wide open 
throttle (WOT) position. 
Does the scan tool indicate APP sensor 1 voltage 
within the specified values?

0.24-

4.49 V

Go to Step 4

Go to Step 6

4

1. Turn OFF the ignition for 30 seconds.  

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

3. Select the DTC option using the scan tool.  

4. Lightly touch and move the related engine 

wiring harnesses and connectors while 

-

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls Diagnosis (DTC P0507 (TAC) To DTC U0107) - 4.8L, 5.3L, and 6.0L - 

Hummer H2