Hummer H2. Manual — part 1582

DTC P2125

Circuit Description

The accelerator pedal position (APP) sensor 2 is a potentiometer type sensor 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 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 2 signal or the APP sensor 5-volt reference voltage is outside the predetermined range, this DTC
sets.

Conditions for Running the DTC

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

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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

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The APP sensor 2 voltage is less than 0.24 volt or more than 4.49 volts.

OR

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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

18

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 19

19

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

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
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.

2: The throttle position (TP) sensor 2 and the APP sensor 2 share a common 5-volt reference source.
Diagnose DTC P0220 first if that DTC is also set.

6: Measuring the specified voltage at the APP sensor harness connector verifies the integrity of the APP
sensor 2 signal circuit from the TAC module.

18: This test determines whether or not the TAC module can recognize a change in signal voltage.

19: There are 2 separate 5-volt reference sources within the TAC module. The TP sensor 1 and the APP
sensor 1 share one 5-volt reference source. The TP sensor 2 and the APP sensor 2 share another common
5-volt reference source. This test determines whether the signal circuit is shorted to any one of the 5-volt

2004 Hummer H2

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

Hummer H2

reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.

20: The previous step found the signal circuit and a 5-volt reference circuit shorted together. This test
isolates whether the short is 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 P2125

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 of the accelerator
pedal.

2. Observe the accelerator pedal position (APP)

sensor 2 voltage parameter with a scan tool.

Does the scan tool indicate the APP sensor 2 voltage
is within the specified values?

IMPORTANT:

If DTCs P0220 or U0107 is also set, refer to
Diagnostic Trouble Code (DTC) List and diagnose
the applicable DTC first.

0.24-

2.24 V

Go to Step 3

Go to Step 6

3

Fully depress the accelerator pedal to the wide open
throttle (WOT) position.
Does the scan tool indicate the APP sensor 2 voltage
is within the specified values?

0.24-

4.49 V

Go to Step 4

Go to Step 6

4

1. Turn OFF the ignition for 15 seconds.

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

3. Observe the DTC info with a scan tool.

4. Lightly touch and move the related engine

wiring harnesses and connectors for the APP
sensor while observing the DTC status.

5. If the scan tool indicates this DTC failed this

ignition during the above test, repair the
intermittent condition as necessary. Refer to
Wiring Repairs and Connector 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

Wiring Systems.

Did you find and correct the condition?

Go to Step 25

Go to Step 5

5

Slowly depress the accelerator pedal to WOT, then
slowly return the pedal to closed throttle while
observing the DTC status.
Did the scan tool indicate this DTC failed this
ignition during the above test?

-

Go to Step 21

Go to Diagnostic

Aids

6

1. Disconnect the APP sensor harness connector.

2. Test the APP sensor 2 signal circuit for

voltage with a DMM.

Does the DMM indicate the APP sensor 2 signal
voltage is within the specified values?

3.94-

6.06 V

Go to Step 11

Go to Step 7

7

1. Turn OFF the ignition.

2. Disconnect the throttle actuator control (TAC)

module harness connector containing the APP
sensor circuits.

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

4. Test the APP sensor 2 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 8

8

Test the APP sensor 2 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 9

9

Test the APP sensor 2 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 10

10

Test for a short between the APP sensor 2 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 23

11

Test the APP sensor 2 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 16

Go to Step 12

1. Turn OFF the ignition.

2. Disconnect the TAC module harness

2004 Hummer H2

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

Hummer H2