Hummer H1 (2006+). Manual - part 142

OBD-412

On-Board Diagnostics

_____________________________________________

Observe the Freeze Frame/Failure Records for this DTC.

Turn OFF the ignition for 30 seconds.

Start the engine.

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.

Does the DTC fail this ignition?

Go to Step 4

Go to Step 3

Select the DTC option on the scan tool.

Lightly touch and move the related accelerator pedal position
(APP) sensor wiring harnesses and connectors while moni-
toring the DTC information.

Did this DTC fail this ignition during the above test?

Go to Step 8

Go to Intermit-

tent Conditions

Disconnect the APP sensor harness connector.

Turn ON the ignition with the engine OFF.

Test for voltage at the APP sensor 2 5-volt reference circuit
720 (TN) with a DVOM.

Does the DVOM indicate voltage within the specified range?

4.8-5.2

Volts

Go to Step 5

Go to Step 6

Test for voltage at the APP sensor 2 signal circuit 721 (LB) with
a DVOM.

Does the DVOM indicate voltage at the specified value?

5.05 Volts

Go to Step 9

Go to Step 7

Disconnect C75 (ECM) harness connector containing the
APP sensor 2 5-volt reference circuit 720 (TN).

Test the APP sensor 2 5-volt reference circuit 720 (TN) for
an open.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

Disconnect C75 (ECM) harness connector containing the
APP sensor 2 signal circuit 721 (LB).

Test the APP sensor 2 signal circuit 721 (LB) for a short to
ground.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

Repair the intermittent condition, as necessary.

Did you complete the repair?

Go to Step 13

Inspect for poor connections at the harness connector of the APP
sensor.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

Inspect for poor connections at the harness connector of the APP
sensor.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

Replace the faulty APP sensor assembly.

Did you complete the replacement?

Go to Step 13

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 13

Step

Action

Value(s)

Yes

_____________________________________________

On-Board Diagnostics OBD-413

5745804

Clear the DTCs with a scan tool.

Turn OFF the ignition for 30 seconds.

Start the engine.

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 14

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to the Diag-

nostic Trouble

Code

System OK

Step

Action

Value(s)

Yes

6-1-05

OBD-414

On-Board Diagnostics

_____________________________________________

DTC P2128 Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage (Figure OBD-108)

Figure OBD-108: Accelerator Pedal Position (APP) Sensor 2 Circuit

Circuit Description

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of 3 indi-
vidual sensors within 1 housing. Three separate signal, low reference, and 5-volt reference circuits are used in order to interface
the APP sensor with the engine control module (ECM). Each sensor has a unique functionality to determine the pedal position as
shown in the table below. The ECM uses the APP sensor to determine the amount of acceleration or deceleration desired by the
person driving the vehicle via the fuel injector control. If the ECM determines high voltage with the APP sensor 2 circuit, DTC
P2128 sets.

_____________________________________________

On-Board Diagnostics OBD-415

5745804

Conditions for Setting the DTC

• The APP sensor 2 voltage is more than 4.75 volts.

• The above condition is present for less than 1 second.

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 informa-

tion in the Failure Records.

• If one or more APP sensor DTCs are set for a single APP sensor, the following occurs:

• The control module will not command Reduced Engine Power mode.

• The control module will use the remaining two APP sensors to calculate throttle response.

• If certain multiple APP sensor DTCs are set for more than one 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 message center displays Reduced Engine Power.

• If all three APP sensors are out of range, the following occurs:

• The control module commands Reduced Engine Power mode.

• 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 re-

lated diagnostic.

• Clear the DTC with a scan tool.

APP

Sensor

ActualPedal

Position

% Depressed as Observed

on a Scan Tool

Voltage as Observed on a

Scan Tool

Pedal at rest

.52 - .80

Pedal at full travel

100

2.12 - 2.78

Pedal at rest

4.25 - 4.53

Pedal at full travel

100

2.24 - 2.93

Pedal at rest

3.95 - 4.13

Pedal at full travel

100

2.69 - 3.16

Step

Action

Value(s)

Yes

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnos-

tic System

Check

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