Hummer H2. Manual - part 1680

monitoring the DTC information.  

Did this DTC fail this ignition during the above test?

Go to Step 24

Go to Step 5

5

1. Continue to observe the DTC information.  

2. Depress the accelerator pedal to WOT, then 

return the pedal to the rest position.  

Did this DTC fail this ignition during the above test?

-

Go to Step 19

Go to Diagnostic 

Aids

6

Disconnect the APP sensor harness connector. 
Does the scan tool indicate the APP sensor 1 voltage 
is at the specified value?

0 V

Go to Step 7

Go to Step 11

7

Connect a test lamp between the APP sensor 1 signal 
circuit and B+. 
Does the scan tool indicate the APP sensor 1 voltage 
is at the specified value?

5 V

Go to Step 8

Go to Step 13

8

Test the APP sensor 1 5-volt reference circuit for 
voltage with a DMM. 
Does the DMM indicate voltage within the specified 
values?

4.54-

5.21 V

Go to Step 10

Go to Step 9

9

1. Turn OFF the ignition.  

2. Disconnect the throttle actuator motor harness 

connector.  

3. Remove the air inlet duct from the throttle 

body assembly.  

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

5. Rotate the throttle blade by hand to WOT and 

hold.  

6. Test the APP sensor 1 5-volt reference circuit 

for voltage with a DMM.  

Does the DMM indicate voltage within the specified 
values?

4.54-

5.21 V

Go to Step 21

Go to Step 16

10

1. Connect a fused jumper between the APP 

sensor 1 low-reference circuit and the APP 
sensor 1 5-volt reference circuit.  

2. Observe the throttle position (TP) sensor 1 

voltage parameter with a scan tool.  

Does the scan tool indicate TP sensor 1 voltage at the 
specified value?

0 V

Go to Step 19

Go to Step 17

1. Turn OFF the ignition.  

2. Disconnect the throttle actuator control (TAC) 

 

2004 Hummer H2 

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

Hummer H2

  

11

module harness connector containing the APP 
sensor circuits.  

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

4. Test the APP sensor 1 signal circuit for a short 

to voltage with a DMM. Refer to Circuit 
Testing and Wiring Repairs in Wiring 
Systems.  

Did you find and correct the condition?

-

Go to Step 25

Go to Step 12

12

1. Turn OFF the ignition.  

2. Disconnect the other TAC module harness 

connector.  

3. Test for a short between the APP sensor 1 

signal circuit and all other TAC module 
circuits with a DMM. Refer to Circuit Testing 
and Wiring Repairs in Wiring Systems.  

Did you find and correct the condition?

-

Go to Step 25

Go to Step 22

13

1. Turn OFF the ignition.  

2. Disconnect the TAC module harness connector 

containing the APP sensor circuits.  

3. Test the APP sensor 1 signal circuit for an 

open or high resistance with a DMM. Refer to 
Circuit Testing and Wiring Repairs in 
Wiring Systems.  

Did you find and correct the condition?

-

Go to Step 25

Go to Step 14

14

Test the APP sensor 1 signal circuit for a short to 
ground with a DMM. Refer to Circuit Testing and 
Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 25

Go to Step 15

15

1. Turn OFF the ignition.  

2. Disconnect the other TAC module harness 

connector.  

3. Test for a short between the APP sensor 1 

signal circuit and all other TAC module 
circuits with a DMM. Refer to Circuit Testing 
and Wiring Repairs in Wiring Systems.  

Did you find and correct the condition?

-

Go to Step 25

Go to Step 22

1. Turn OFF the ignition.  

2. Disconnect the TAC module connector 

containing the APP sensor circuits.  

 

2004 Hummer H2 

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

Hummer H2

  

16

3. Test the APP sensor 1 5-volt reference circuit 

for the following conditions with a DMM: 

z

An open  

z

A short to ground  

z

High resistance 

Refer to Circuit Testing and Wiring 
Repairs in Wiring Systems. 

Did you find and correct the condition?

-

Go to Step 25

Go to Step 22

17

1. Disconnect the TAC module connector 

containing the APP sensor circuits.  

2. Test the APP sensor 1 low-reference circuit for 

an open or high resistance with a DMM. Refer 
to Circuit Testing and Wiring Repairs in 
Wiring Systems.  

Did you find and correct the condition?

-

Go to Step 25

Go to Step 18

18

Test the TAC module ground circuit for an open or 
high resistance with a DMM. Refer to Circuit 
Testing and Wiring Repairs in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 25

Go to Step 22

19

Inspect for poor connections at the harness connector 
of the APP sensor. Refer to Testing for Intermittent 
Conditions and Poor Connections and Repairing 
Connector Terminals in Wiring Systems. 
Did you find and correct the condition?

-

Go to Step 25

Go to Step 20

20

Replace the APP sensor assembly. Refer to 
Accelerator Pedal Position (APP) Sensor 
Replacement . 
Did you complete the replacement?

-

Go to Step 25

-

21

Did DTC P0120 set while performing Step 9?

-

Go to DTC 

P0120

Go to Step 22

22

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

-

Go to Step 25

Go to Step 23

23

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

-

Go to Step 25

-

24

Repair the intermittent condition as necessary. Refer 
to Connector Repairs and Wiring Repairs in 

-

 

2004 Hummer H2 

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

Hummer H2

  

DTC P2121 

Circuit Description 

The accelerator pedal position (APP) sensor 1 and APP sensor 2 are potentiometer type sensors, each with the 
following circuits: 

z

A 5-volt reference circuit  

z

A low reference circuit  

z

A signal circuit  

The control module provides the APP sensors a 5-volt reference circuit and a low reference circuit. The APP 
sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 
signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is also low 
at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 signal 
and the APP sensor 2 signal circuits are out of correlation, this DTC sets. 

Conditions for Running the DTC 

z

DTCs P0606, P2108, or 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

APP sensor 1 disagrees with APP sensor 2 by more than 10.5 percent.  

z

The above condition is present for more than 1 second. 

Wiring Systems. 
Did you complete the repair?

Go to Step 25

-

25

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 26

26

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