Hummer H1 (2006+). Manual - part 349

12-72

Electrical System

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Pull the CTIS module out enough to gain access to the wiring harness and air lines that attach to the back of the module.

Note the position of the two air lines on the back of the air pressure gauge and disconnect them. Tagging the lines prior to
removal to assure proper installation is recommended.

Disconnect connector C12 from the instrument panel harness and remove the CTIS module.

Installation

Connect connector C12 to the instrument panel harness.

Install the air pressure lines to the back of the air pressure gauge. Make sure to install lines in the same position as they were
removed.

Install the CTIS module in the instrument panel and secure with four allen screws.

CTIS Air Pressure Gauge Replacement

WARNING: The CTIS system components are subject to high air pressure. Always relieve the air pressure prior to
servicing the CTIS system. Failure to follow this warning may result in serious injury.

Removal

Remove the center dash assembly bezel.

Remove the two air lines at the quick disconnects.

Remove the air pressure gauge back lighting bulb.

Remove the two retainer nuts that secure the air pressure gauge retainer bracket (Figure 12-55).

Remove the air pressure gauge retainer bracket and the air pressure gauge from the bezel.

Figure 12-55: CTIS Module Break Down

Installation

Install the air pressure gauge, retainer bracket and the nuts.

Install the air pressure gauge back lighting bulb.

Install the air lines and the bezel.

Inflate/Deflate and Tire Selector Switch Replacement.

WARNING: The CTIS system components are subject to high air pressure. Always relieve the air pressure prior to
servicing to the CTIS system. Failure to follow this warning may result in serious injury.

04-S06-010

QUICK

DISCONNECT

CENTER

DASH

BEZEL

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Electrical System 12-73

Removal

Remove the CTIS module.

Disconnect the harness from the back of the inflate/deflate switch and the tire selector switches.

Remove the inflate/deflate and tire selector switches from the CTIS module.

Installation

Install the inflate/deflate and tire selector switches from the CTIS module.

Install the harness connector to the back of the inflate/deflate switch and the tire selector switches.

Install the CTIS module.

Air Pressure Gauge Back Lighting

The air pressure gauge back lighting is the only lighting component that is serviceable on the CTIS control unit. To service the bulb
in the air pressure gauge, pull the harness and bulb socket out of the back of the air pressure gauge. With the harness and bulb
socket removed from the air pressure gauge, twist the bulb a quarter of a turn from the harness receiver and remove the bulb.

Warning/Indicator “Bulb Check”

When the ignition is turned to the “Run” position the “Bulb Check” should operate. The “Bulb Check” is a 4.1 second test to see
that all indicator and warning lights are functioning. The test signal is a battery voltage signal supplied on circuit 915 (LB). If the
“Bulb Check” fails to operate refer to the diagnostic chart.

Warning/Indicator Lights for the CTIS module.

The LEDs on the CTIS module receive a ground on circuit 59 (BK). The control side of these LEDs is a voltage signal.

The warning/indicator lights are also connected to a 4.1 second “Bulb Check”. This is achieved by a voltage signal being supplied
to the module through circuit 912 (DB). When the module receives the voltage signal it activates an internal timer which activates
the LEDs (Figure 12-99).

CTIS Air Compressor Indicator Light

The CTIS air compressor indicator light is a green LED. It is controlled by a voltage signal supplied on circuit 46 (WH). When the
signal is present on this circuit the CTIS module makes the LED blink.

Low Air Warning Light

The low air warning light is a red LED. It is controlled by a voltage signal supplied by either the front pressure switch or the rear
pressure switch on circuit 46 (WH).

HVAC ELECTRICAL SYSTEM

HVAC Main Blower Inoperative ALL Except High (Figure 12-90)

Step

Action

Value(s)

Yes

Ignition on, blower switch set to Med 2, mode
dial set to face. Measure voltage on the yellow
wire (CKT 754) at the blower relay. Is voltage
present?

8 -10v

Replace the blower

relay.

Go to step 2.

Ignition on, blower switch set to Med 2, mode
dial set to face. Measure voltage on the grey wire
(CKT 752) at the blower resistor. Is voltage
present?

+12v

Replace the blower

resistor.

Go to step 3.

12-74

Electrical System

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Ignition on, blower switch set to Med2, mode dial
set to face. Measure voltage on the grey wire
(CKT 752) at the back of the HVAC control head.
Is voltage present?

+12v

Repair open, bad

connection or short

to ground in CKTs

751, 752, and 755

between HVAC

control head and

resistor block.

Replace control

head.

HVAC Compressor Inoperative (Figure 12-123)

Step

Action

Value(s)

Yes

Perform On-board diagnostic system check. Is
system functioning properly?

Go to step 2.

Diagnose problem in

on-board diagnostic

system first.

Does A/C system have an adequate charge?

Go to step 3.

Diagnose leak and

recharge.

Is engine in an overheated condition?

Cool down and

recheck.

Go to step 4.

Connect scan tool to vehicle. Ignition on, find
misc. tests and command compressor clutch on.
Does clutch come on?

Go to step 10.

Go to step 5.

Disconnect the compressor clutch. Connect a test
lamp to ground, and probe the brown wire at the
clutch connector. Using the scan tool, command
the clutch on. Does the test light come on?

Replace the com-

pressor clutch.

Go to step 6.

Remove A/C relay from the exterior fuse box.
Using a DVOM, set to measure voltage, ignition
on, check for voltage on the green wire (CKT
400) at the relay in the exterior fuse box. Is volt-
age present?

+12v

Go to step 7.

Repair open, bad

connection or short

in CKT400 between

exterior fuse box and

ignition switch.

Using a DVOM, set to measure voltage, place the
positive lead on a battery power source. Place the
ground lead on the dark green wire (CKT 440) at the
relay. Using the scan tool, command the compressor
clutch on. Does meter display battery voltage?

+12v

Go to step 8.

Go to step 9.

Using a DVOM, set to measure resistance. Check
resistance on the brown wire (CKT 348) at the
relay, and the brown wire (CKT 348) at the com-
pressor clutch connector. Is resistance below
specification?

<.2

Replace compressor

relay.

Repair open or bad
connection in CKT

348 between clutch

relay and compres-

sor clutch.

Ignition on, using a DVOM, set to measure volt-
age, backprobe the dark green wire in C27 at the
ECM (CKT 440) with the negative lead. Place the
positive lead on a battery voltage source. Using
the scan tool, command the compressor clutch on.
Does the meter display battery voltage?

+12v

Repair open, or bad

connection in CKT

440 between ECM

and A/C clutch relay.

Replace the ECM.

HVAC Main Blower Inoperative ALL Except High (Figure 12-90)

Step

Action

Value(s)

Yes

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Electrical System 12-75

Ignition on, locate engine data list, and “A/C
Request”. Turn mode dial on HVAC control head
to MAX A/C. Does scan tool display indicate A/C
request?

Replace ECM.

Go to step 11.

Ignition on, mode dial set to MAX A/C. Using a
DVOM, set to measure voltage, backprobe the tan
wire (CKT 198) at the temperature cutout switch
on the HVAC unit with the positive probe. Place
the negative lead on a known good ground. Is
voltage present?

+12v

Go to step 14.

Go to step 1.

Ignition on, mode dial set to MAX A/C. Using a
DVOM, set to measure voltage, backprobe the
yellow wire (CKT 347) at the temperature cutout
switch on the HVAC unit with the positive probe.
Place the negative lead on a known good ground.
Is voltage present?

+12v

Replace the tempera-

ture cutout switch.

Go to step 13.

Using a DVOM, set to measure voltage, ignition
on, mode dial set to MAX A/C, backprobe for
voltage on the yellow wire (CKT 347) in the 8
wire connector at the rear of the HVAC control
head. Is voltage present?

+12v

Repair open, bad

connection or short

in CKT 347 between

HVAC control head

and temperature cut-

out switch.

Replace control

head.

Ignition on, mode dial set to MAX A/C. Discon-
nect the high pressure cutout switch on the com-
pressor. Using a DVOM, set to measure voltage,
check for voltage on the tan wire (CKT 198). Is
voltage present?

+12v

Go to step 15.

Repair open, bad

connection, or short

in CKT 198 between

temperature cutout

switch and high

pressure cutout

switch.

Using a DVOM, set to measure resistance, check
continuity across the two pins on the high pres-
sure cutout switch. Is resistance below specifica-
tion?

<.2

Go to step 16.

Replace the high

pressure cutout

switch.

Ambient temperature above 45°. Disconnect the
ambient temperature switch. Using a DVOM, set
to measure resistance, measure continuity across
the ambient temperature switch terminals. Is
resistance below specification?

<.2

Go to step 17.

Replace ambient

temperature switch.

Disconnect low pressure cutout switch. Using a
DVOM, set to measure resistance, measure conti-
nuity across the low pressure cutout switch. Is
resistance below specification?

<.2

Repair open, bad

connection or short

in CKT 439 between

high pressure cutoff

switch and ECM.

Replace the low

pressure cutout

switch.

HVAC Compressor Inoperative (Cont’d) (Figure 12-123)

Step

Action

Value(s)

Yes

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