Hummer H3. Manual — part 933

DTC P1574

Circuit Description

This diagnostic test functions on the assumption that a sudden decrease in vehicle speed is caused
by a brake pedal application. When the powertrain control module (PCM) detects that there is a
4.2 km/h (2.6 mph) or greater decrease in vehicle speed within 0.25 seconds and a transition of
the torque converter clutch (TCC) brake/cruise release switch without a transition of the stop
lamp switch, the PCM sets DTC P1574.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1574 Stop Lamp Switch Circuit

Conditions for Running the DTC

DTCs P0502, P0503, P0719 and P0724 are not set.

The engine speed is greater than 700 RPM.

The Traction Control System (TCS) or the Antilock Brake System (ABS) are not active and
have not failed.

The vehicle speed is greater than 48 km/h (30 mph) in order to enable the diagnostic.

The diagnostic will disable when the wheel speed is less than 16 km/h (10 mph).

Conditions for Setting the DTC

The vehicle speed decreases by at least 4.2 km/h (2.6 mph) within 0.25 seconds.

The PCM detects a TCC brake/cruise release switch transition.

The PCM does not detect a stop lamp switch transition.

Action Taken When the DTC Sets

The PCM sets the stop lamp switch status to released.

The PCM disables the operation of the Cruise Control System.

Conditions for Clearing the DTC

A history DTC will clear after 40 malfunction free warm-up cycles, if failures are not

Does the DTC reset?

Go to Step 2 System OK

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Cruise Control - H3

reported by this or any other emission related diagnostic.

The PCM receives a clear code command from the scan tool.

Diagnostic Aids

Inspect for proper adjustment of the TCC brake/cruise release switch. Refer to Cruise
Release Switch Adjustment.

Refer to Exterior Lighting Systems Description and Operation in order to avoid a
misdiagnosis.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor
Connections .

DTC P1574

Step

Action

Yes

No

Schematic Reference : Cruise Control Schematics
Connector End View Reference: Cruise Control Connector End Views

1

Did you perform the Diagnostic System
Check - Vehicle?

Go to Step 2

Go to
Diagnostic
System Check -
Vehicle

2

Do the stop lamps operate properly?

Go to Step 3

Go to Stop
Lamps
Inoperative or
Stop Lamps
Always On

3

Test the stop lamp switch signal circuit for
an open or the high resistance. Refer to
Circuit Testing and Wiring Repairs .
Did you find and complete the repair?

Go to Step 6

Go to Step 4

4

Inspect for poor connections at the harness
connector of the powertrain control
module (PCM). Refer to Testing for
Intermittent Conditions and Poor
Connections and Connector Repairs .
Did you find and correct the condition?

Go to Step 6

Go to Step 5

5

Replace the PCM. Refer to Control
Module References for replacement,
setup and programming.

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Cruise Control - H3

SYMPTOMS - CRUISE CONTROL

Perform the Diagnostic System Check - Vehicle before using the Symptom Tables in order to
verify that all of the following are true:

There are no DTCs set.

The control modules can communicate via the serial data link.

Review the system description and operation in order to familiarize yourself with the system
functions. Refer to Cruise Control Description and Operation.

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the Cruise Control
System. Refer to Checking Aftermarket Accessories .

Inspect the easily accessible or visible system components for obvious damage or conditions
which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to Cruise Control Inoperative/Malfunctioning in order to diagnose a symptom.

CRUISE CONTROL INOPERATIVE/MALFUNCTIONING

Diagnostic Aids

Perform the following in order to avoid a misdiagnosis:

Did you complete the replacement?

Go to Step 6

-

6

1. Use the scan tool in order to clear the

DTCs.

2. Operate the vehicle within the

Conditions for Running the DTC.

Does the DTC reset?

Go to Step 2

System OK

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Cruise Control - H3

Ensure that the following cruise control switches are not stuck in the engaged position:

On/off switch

Set/coast switch

Resume/accel switch

Inspect for proper operation of the stop lamps. Refer to Exterior Lighting Systems
Description and Operation .

Inspect for proper adjustment of the TCC brake/cruise release switch. Refer to Cruise
Release Switch Adjustment.

Inspect for proper adjustment of the clutch release switch. Refer to Clutch Pedal Cruise
Control Release Switch Adjustment.

Inspect for proper operation of the clutch pedal.

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor
Connections .

Cruise Control Inoperative/Malfunctioning

Step

Action

Values

Yes

No

Schematic Reference: Cruise Control Schematics
Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic
System Check - Vehicle?

-

Go to Step 2

Go to
Diagnostic
System
Check -
Vehicle

2

1. Install a scan tool.

2. Turn ON the ignition, with the

engine OFF.

3. Turn the cruise control On/Off

switch Off.

4. With the scan tool, observe the

following cruise control
parameters in the Cruise
Control Data list:

Cruise On/Off Switch

Cruise Resume/Accel
Switch

-

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Cruise Control - H3