Hummer H1 (2002+). Manual - part 290

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PCM/Tech 1 Scan Tool 93

05745159

DTC P0568 Cruise Set Circuit

Circuit Description

The cruise Set/Coast switch is an input to the fuel control por-
tion of the PCM. These inputs allow the PCM to control and
hold a requested speed. Cruise Set/Coast switch sends an igni-
tion voltage signal to the PCM when the Set/Coast switch is
“ON”. This is a type D DTC.

Conditions for Setting the DTC

• Cruise switch “OFF”.

• Ignition voltage on Set switch signal circuit.

• Cruise switch “ON”.

• Set switch “ON” for longer than 25.5 seconds

Action Taken When the DTC Sets

• The PCM will disallow all cruise inputs.

• TCC shift schedules may be affected.

Conditions for Clearing the MIL/DTC

• A History DTC will clear when forty consecutive

warm-up cycles that the diagnostic does not fail (coolant
temperature has risen 5°C (40°F) from start up coolant
temperature and engine coolant temperature exceeds
71°C (160°F) that same ignition cycle).

• Use of a Scan Tool.

Diagnostic Aids

If the Set/Coast switch stuck in the “ON” position or the driver
is holding the Set/Coast switch “ON” for longer than 25.5 sec-
onds, DTC P0569 will set. DTC P0568 only checks the signal
circuit for a short to voltage.

Test Description

Number(s) below refer to the number(s) on the diagnostic ta-
ble.

2. This step determines if the signal circuit is shorted to volt-

age.

FUSE 5C
10AMP
INTERIOR

FUSE 3A
10 AMP
EXTERIOR

ON/
OFF

SET
COAST

RESUME
ACCEL

HOT IN RUN
AND START

C29-A11

C29-B11

C27-D10

C28-D14

C28-C2

C27-D12

C27-D3

C27-D4

C27-D6

C29-B2

C29-B1

C27-C5

C29-A12

C5-D3

C5-A4

154 TN

151 GY

152 DB

153 LG

ON / OFF
SIGNAL

SET
COAST
SIGNAL

RESUME
ACCEL
SIGNAL

WASTEGATE
SOLENOID
CONTROL

5 VOLT
REFERENCE

APP 3
SIGNAL

GROUND

APP 1
SIGNAL

GROUND

720 TN

717 WH

723 YL

724 DG

725 GY

718 DB

719 BR

721 LB

722 PP

ACCELERATIOR
PEDAL POSITION
SENSOR

POWERTRAIN
CONTROL
MODULE
(PCM)

APP 2
SIGNAL

9-S12-055

295 BR

GRN

PCM/Tech 1 Scan Tool

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3. This step determines if the PCM or switch is at fault.

DTC P0568 - Cruise Set Circuit

Step

Action

Value(s)

Yes

Important:

Before clearing DTC(s) use the scan tool “Capture Info” to

record freeze frame and failure records for reference, as data will be lost
when “Clear Info” function is used.

Was the “On-Board Diagnostic (OBD) System Check” performed?

—

Go to Step 2.

Go to OBD

System Check.

1. Scan tool connected.
2. Ignition “ON”, engine “OFF”.

3. Cruise switch “OFF”.

Does scan tool display Set switch “ON”?

—

Go to Step 3.

Go to Step 4.

1. Ignition “ON”.
2. Disconnect the PCM brown 24 way connector.

3. Probe the Set switch signal circuit at the PCM harness with a test light

connected to chassis ground.

Is the test light “ON”?

—

Go to Step 5.

Go to Step 7.

DTC is intermittent. If no additional DTCs are stored, refer to “Diagnostic
Aids”. If additional DTCs are stored, refer to those charts(s) first.

Are additional DTCs stored?

—

Go to the

applicable

DTC table

Go to

Diagnostic

Aids

1. Resume switch signal circuit is shorted to voltage.
2. Repair as necessary.

Is action complete?

—

Go to Step 8.

—

Replace the faulty PCM. Notice: If the PCM is faulty, the new PCM must
be programmed. Go to PCM replacement and programming procedures.

Is the action complete?

—

Go to Step 7.

—

1. Using the Scan Tool, select “DTC”, “Clear Info”.
2. Start engine and idle at normal operating temperature.

3. Select “DTC”, “Specific”, then enter the DTC number which was set.

4. Operate vehicle within the conditions for setting this DTC as specified

in the supporting text.

Does the Scan Tool indicate that this diagnostic Ran and Passed?

—

Go to Step 8.

Go to Step 2.

Using the Scan Tool, select “Capture Info”, “Review Info”.

Are any DTCs displayed that have not been diagnosed?

—

Go to the

applicable

DTC table

System OK.

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PCM/Tech 1 Scan Tool 95

05745159

DTC P0571 Cruise Brake Switch Circuit

Circuit Description

The TCC normally closed brake switch supplies a B+ signal on
CKT 810 to the PCM. The circuit is opened when the brakes
are applied. The stop lamp/cruise control normally open brake
switch supplies a B+ signal on CKT 22 to the PCM when the
brake is applied. This is a type D DTC.

Conditions for Setting the DTC

• Switches disagree for 10 consecutive minutes.

• TCC and cruise control brake switches are not toggling

“open” and “closed” during 6 brake applications on
same ignition cycle.

Action Taken When the DTC Sets

Fourth gear operation in hot mode, and cruise control opera-
tion.

Conditions for Clearing the MIL/DTC

• A History DTC will clear when forty consecutive

• Use of a scan.

Diagnostic Aids

Refer to PCM Intermittent Diagnostic Trouble Codes or Per-
formance. Check customer driving habits and/or unusual traf-
fic conditions (i.e. stop and go, expressway traffic).

Test Description

Number(s) below refer to the number(s) on the diagnostic ta-
ble.
3. This test simulates brake switch closed or brakes “OFF”.
4. This test checks the feed circuit.

FUSE 4D

15 AMP

INTERIOR

FUSE 6B

5 AMP

INTERIOR

HOT AT
ALL TIMES

HOT IN RUN
AND START

STOP LAMP
SWITCH

TCC CRUISE
BRAKE SWITCH

TO
STOP
LAMPS

10 OR

291 PK

22 RD

810 PP

STOP

LAMP

SIGNAL

TCC/ CRUISE

BRAKE SIGNAL

FUSE 2C

10 AMP

INTERIOR

HOT IN RUN
AND START

C1-1

A/C COMPRESSOR

ENABLE

RELAY CONTROL

A/C
COMPRESSOR
CLUTCH

DIODE

C5-8

400 LG

A/C COMPRESSOR

CLUTCH RELAY

EXTERIOR

FUSE

BOX

440 RD

59 BK

348 BR

C28-D5

HVAC

CONTROL

MODULE

C6-J8

347 YL

A/C

REQUEST

SIGNAL

TEMPERATURE

CUTOUT

SWITCH

HVAC

UNIT

C1-39

C4-2

198 TN

C4-5

438 OR

439 YL

C27-C2

A/C

REQUEST

SIGNAL

COMPRESSOR

HIGH

PRESSURE

CUTOUT

SWITCH

AMBIENT
TEMP
CUTOUT
SWITCH

LOW
PRESSURE
CUTOUT
SWITCH

9-S12-054

PCM/Tech 1 Scan Tool

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DTC P0571 - Cruise Brake Switch Circuit

Step

Action

Value(s)

Yes

Important:

Before clearing DTC(s) use the scan tool “Capture Info”

Was the “On-Board Diagnostic (OBD) System Check” performed?

—

Go to Step 2.

Go to OBD

System Check.

1. Scan tool installed.
2. Ignition “ON”, engine “OFF”.
3. Apply brakes.
Does scan tool display Cruise Brake switch “Closed” and then “Open” when
brake is released?

—

Go to Step 3.

Go to Step 4.

Apply brakes again.
Does scan tool display Brake switch “Closed” and then “Open” when brake is
released?

—

Go to Step 8.

Go to Step 6.

1. Ignition “ON”, engine “OFF”.
2. Stop lamp switch disconnected.
3. With test light connected to ground, probe normally open feed circuit (termi-

nal “B”). Is the test light “ON”?

—

Go to Step 5.

Go to Step 9.

1. Disconnect stop lamp switch.
2. Jumper normally open (terminal “A”) feed circuit and the normally open sig-

nal circuits (terminal “B”) together.

Does scan tool display Cruise Brake switch “Closed”?

—

Go to Step 6.

Go to Step 10.

1. Ignition “ON”, engine “OFF”.
2. Stop lamp switch disconnected.
3. With test light connected to ground, probe normally closed feed circuit (ter-

minal “F”).

Is the test light “ON”?

—

Go to Step 7.

Go to Step 12.

1. Stop lamp switch disconnected.
2. Jumper normally closed (terminal “F”) feed circuit and the normally closed

signal circuits (terminal “E”) together.

Does scan tool display Cruise Brake switch “Closed”?

—

Go to Step 6.

Go to Step 14.

DTC is intermittent. If no additional DTCs are stored, refer to “Diagnostic
Aids”. If additional DTCs are stored, refer to those charts(s) first.
Are additional DTCs stored?

—

Go to

applicable

DTC table.

Go to

Diagnostic Aids

Check normally open signal circuit (terminal “B”) for an open or short to
ground.
Is action complete?

—

Go to Step 17.

—

Check normally open Cruise Brake switch signal circuit for an open or short to
ground.
Was a repair performed?

—

Go to Step 17. Go to Step 11.

Check normally open Cruise Brake switch signal circuit for a poor connection
at PCM.
Was a repair performed?

—

Go to Step 17. Go to Step 16.

Check normally closed feed circuit (terminal “F”) for an open or short to
ground.
Is action complete?

—

Go to Step 17.

—

Check normally closed Cruise Brake switch signal circuit for an open or short
to ground.
Was a repair performed?

—

Go to Step 17. Go to Step 14.

Check normally closed Cruise Brake switch signal circuit for a poor connection
at PCM.
Is action complete?

—

Go to Step 17.

—

Replace stop lamp switch.
Is action complete?

—

Go to Step 17.

—

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