Hummer H1 (2006+). Manual - part 224

6-46

Wheels and Tires/Central Tire Inflation System (CTIS)

_______________

CTIS Leak Detection Test

1.

Start the engine and inflate the front and rear tires to 40 psi (276 kPa).

2.

Turn the tire selector switch to OFF.

3.

Turn the engine OFF.

4.

Remove the air vent line located at the air intake horn and listen for air escaping through the vent line.

5.

Remove the transmission dipstick from the dipstick tube and listen for air or transmission fluid escaping through the dipstick
tube.

6.

If air or fluid is detected in steps 4 or 5, inspect the steering arm cover seals using the CTIS leak isolation test.

CTIS Leak Isolation Test

1.

Start the engine and inflate the front and rear tires to 40 psi (276 kPa).

2.

Turn the tire selector switch to OFF.

3.

Turn the engine OFF.

4.

Close (release) all four wheel quick-disconnect valves.

5.

Remove the vent line from one geared hub.

6.

Open (engage) the quick-disconnect valve at this wheel to allow air pressure from the tire to enter bored passage inside the
geared hub.

7.

Listen for escaping air around the steering arm seal through the geared hub vent opening.

8.

If air is escaping through the vent line fitting, replace the steering arm seal (Section 8).

9.

Inspect the other three geared hubs using steps 5, 6, 7, and 8 above.

10. Replace the defective seals as required, then retest system.

CTIS Leak Down Testing

NOTE: Suspected air loss in the CTIS after the vehicle has been parked for several days may be attributed to one of the following:
improperly seated O-rings, loose air line connection(s), quick-disconnect valve(s) not connected, tire leak(s), faulty valve(s), or a
faulty steering arm cover seal. Suspected air leak(s) may be detected using a soap/water solution or equivalent. O-rings that appear
to be cut, distorted, or suspected of leaking should be replaced. When traversing off road in extremely muddy terrain, the dust ex-
cluder should be inspected for trapped mud.

1.

Verify the quick-disconnect valves are connected to the wheels.

2.

Apply the parking brake. Start the engine and allow to idle.

3.

Place the tire selector switch to BOTH position and inflate/deflate switch to the INFLATE position.

4.

Observe the air pressure gauges until the air pressure reaches 40 psi (276 kPa).

5.

Place the inflate/deflate switch to the OFF position, and stop the engine.

Inspect the quick-disconnect valve,
quick-disconnect valve nut, tube, nut
and sleeve assembly, insert, and el-
bow for damage (Figure  6-72).

Quick-disconnect compo-
nent is frayed, stripped,
cracked, or broken.

Replace the
component.

Tighten all connections. If air is still leak-
ing, remove the CTI part, clean, apply new
sealant to the threads, and install the CTI
part.

Inspect the tire for punctures and rim
leaks. Use a soap and water solution to
check for air leaks around the rim of the
tire. Repair or replace the tire as neces-
sary.

Troubleshooting Chart 5– Tire and Quick-Disconnect Valve

______________

 Wheels and Tires/Central Tire Inflation System (CTIS)  6-47

5745804

6.

Record the tire pressure on the instrument panel gauges and the right-rear tire pressure. Compare the recorded pressures to the
readings taken 30 minutes later, If more than one (1) pound has leaked, check the system as described above to detect where
the leak is located.

COMPRESSOR SERVICE

WARNING:  The CTIS components are subject to high air pressure. Always relieve the air pressure before loosen-
ing or removing air system components by disconnecting quick-disconnect valve assemblies. Failure to follow this
warning may result in serious injury.

Removal

1.

Raise and secure the hood.

2.

Disconnect the power and the ground leads from the compressor(Figure  6-52).

3.

Loosen the clamp securing the air intake hose to the fitting and disconnect the hose from the fitting.

4.

Disconnect the compressor-to-air manifold hose from the street tee at the compressor.

5.

Loosen the two clamps securing the compressor to the bracket and remove the compressor.

6.

Remove the street tee from the compressor.

Cleaning and Inspection

Clean and inspect the compressor, leads, fittings, and the mounting hardware. Check for cracks, frayed wire, stripped threads, and
improper operation. Replace the defective parts.

Installation

CAUTION: Do not allow sealant into the air system. Sealant will damage CTIS components.

NOTE: Apply sealant to all the threads before installation.

1.

Install the compressor on the bracket, and secure with two clamps.

2.

Connect the compressor-to-air manifold hose to the street tee.

3.

Connect the air intake hose to the fitting, and secure with the hose clamp.

4.

Connect the power and the ground leads to the compressor.

5.

Check the compressor for correct operation.

6.

Check for any leaks.

7.

Lower and secure the hood.

6-48

Wheels and Tires/Central Tire Inflation System (CTIS)

_______________

Figure 6-52:   CTIS Compressor

CTIS INSTRUMENT CLUSTER

WARNING:  The CTIS components are subject to high air pressure. Always relieve the air pressure before loosen-
ing or removing air system components by disconnecting quick-disconnect valve assemblies. Failure to follow this
warning may result in serious injury.

NOTE: Prior to removal, tag all the harness connectors and air lines for installation.

Removal

1.

Remove the four screws securing the CTIS module to the instrument panel and gain access to the back of the CTIS module.

2.

Disconnect the air lines, the illumination bulb and socket from the back of the air pressure gauge.

3.

Disconnect the harnesses from the back of the inflate/deflate switch and the selector switch.

4.

Disconnect the harness from the CTIS indicator module circuit board.

Module Disassembly

1.

To remove the inflate/deflate switch from the module apply pressure to the back side of the switch and push the switch through the 
plastic bezel. The selector switch can be removed the same way.

2.

Removal of the air pressure gauge is achieved by removing the two retaining nuts.

3.

Remove the retainer bracket and slide the gauge out the front of the module bezel.

Module Assembly 

1.

Install air pressure gauge in the module bezel and position the retainer bracket over the threaded air inlets.

2.

Install the retainer nuts over the air inlets and tighten.

AIR

INTAKE

HOSE

STREET

TEE

COMPRESSOR-TO-AIR

MANIFOLD HOSE

ISOLATOR

UPPER

BRACKET

12-1-05

______________

 Wheels and Tires/Central Tire Inflation System (CTIS)  6-49

5745804

3.

Install the switches by sliding them, harness side first, through the input holes on the CTIS module bezel. A small “pop” should be
heard as the switch seats in the bezel.

Installation

1.

Connect the air pressure lines, illumination bulb and socket, in the original positions, to the back of the air pressure gauge.

2.

Install the harness for the inflate/deflate switch and the selector switch.

3.

Install the harness for the CTIS indicator module circuit board.

NOTE: Be careful not to over tighten the retaining screws.

4.

Position the CTIS module on the instrument panel and secure with the four retaining screws.

INFLATE/DEFLATE AND TIRE SELECTOR SWITCHES

Removal

1.

Remove the CTIS instrument cluster panel.

2.

Disconnect the harness connectors from inflate/deflate switch and tire selector switch (Figure  6-53).

3.

Remove the inflate/deflate and tire selector switches from the CTIS instrument cluster and housing.

Cleaning and Inspection

Clean and inspect the inflate/deflate and the tire selector switches for damage. Replace the defective parts.

Installation

1.

Install the inflate/deflate and the tire selector switches in the housing on the CTIS instrument cluster(Figure  6-53).

2.

Connect the connector to switches.

3.

Install the CTIS instrument cluster panel.

4.

Start the engine and ensure the switches operate properly.

Figure 6-53:   CTIS Module Exploded View

GAUGE RETAINER 

BRACKET

AIR PRESSURE

GAUGE

TIRE SELECTOR

SWITCH

INFLATE/DEFLATE

SWITCH

12-1-05