Hummer H2. Manual - part 1581

Action Taken When the DTC Sets

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

The malfunction indicator lamp (MIL) will not illuminate.

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

If one or more APP sensor DTCs are set for a single APP sensor, 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.

{

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

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
non-emission related diagnostic.

Clear the DTC with a scan tool.

Diagnostic Aids

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.

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.

For an intermittent, refer to Intermittent Conditions .

Test Description

The numbers below refer to the steps numbers in the diagnostic table.

2: This step determines if a communication condition exists.

5: This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator
pedal position. Monitoring the APP angles for sensor 2 and sensor 3 is an accurate way of verifying the
actual position of the pedal. The APP angles for all 3 sensors should be within a few percent of each
other. If the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. If the pedal is fully
depressed, all APP angles should be 100 percent.

6: The APP sensor 1 shares a common 5-volt reference circuit with the throttle position (TP) sensor 1.
Monitoring the TP sensor 1 voltage aids in diagnosing the APP sensor 5-volt reference and low reference
circuits.

9: With the TAC module still connected, this test will help determine a short to the signal circuit either

2004 Hummer H2

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

Hummer H2

within the TAC module or the wiring.

10: This step determines whether the TAC module or a shorted circuit is causing the condition.

19: 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 P2121

Step

Action

Values

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

Is DTCs U0107 also set?

Go to DTC

U0107

Go to Step 3

1. Start the engine.

2. Observe the DTC information with a scan tool.

Did any other throttle actuator control (TAC) module
or accelerator pedal position (APP) sensor DTC set
except P1125?

IMPORTANT:

DO NOT depress the accelerator pedal.

Go to

Diagnostic

Trouble Code

(DTC) List

Go to Step 4

Observe the APP sensor Agree/Disagree parameters
with a scan tool.
Does the scan tool indicate Disagree for any of the
APP Agree/Disagree parameters?

Go to Step 6

Go to Step 5

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

2. Observe the APP sensor angles for both APP

sensors with a scan tool.

3. Slowly depress the accelerator pedal, stopping

at 25, 50, 75, and 100 percent.

4. Slowly release the accelerator pedal, stopping

at 75, 50, 25, and 0 percent.

Does the scan tool indicate APP sensor 1 angle within
10.5 percent of the APP sensor 2 angle during the
above test?

Go to Diagnostic

Aids

Go to Step 6

1. Turn OFF the ignition.

2004 Hummer H2

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

Hummer H2

2. Disconnect the APP sensor harness connector.

3. Connect a fused jumper between the APP

sensor 1 5-volt reference circuit and ground.

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

5. Observe the throttle position (TP) sensor 1

voltage parameter with a scan tool.

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

0.0 V

Go to Step 7

Go to Step 11

1. Connect a fused jumper between the APP

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

2. Observe the TP sensor 1 voltage parameter

with a scan tool.

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

0.0 V

Go to Step 8

Go to Step 12

1. Connect a fused jumper between the APP

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

2. Observe the APP sensor 1 voltage parameter

with a scan tool.

Does the scan tool indicate APP sensor 1 voltage is
near the specified value?

5 V

Go to Step 14

Go to Step 9

Test for a short between the APP sensor 1 signal
circuit and all other APP circuits at the APP sensor
harness connector with a DMM.
Does the DMM indicate a short to another circuit?

Go to Step 10

Go to Step 13

1. Turn OFF the ignition.

2. Disconnect both of the TAC module harness

connectors.

3. Test for a short between the APP sensor 1

signal circuit and all other APP circuits at the
APP sensor harness connector with a DMM.
Refer to Circuit Testing and Wiring Repairs
in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 15

1. Turn OFF the ignition.

2. Disconnect the TAC module harness connector

containing the APP 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

3. Test the APP sensor 1 5-volt 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 18

Go to Step 15

1. Turn OFF the ignition.

2. Disconnect the TAC module harness connector

containing the APP circuits.

3. 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 18

Go to Step 15

1. Turn OFF the ignition.

2. Disconnect the TAC module harness connector

containing the APP 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 an open or high resistance?

Go to Step 18

Go to Step 15

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 18

Go to Step 16

Inspect for poor connections at the harness
connectors 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 18

Go to Step 17

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

Go to Step 18

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

Go to Step 18

1. Clear the DTCs with a scan tool.

2. Turn OFF the ignition for 30 seconds.

2004 Hummer H2

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

Hummer H2

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