A Tire Service and Diagnosis Video (course number is 13044.15V) is available on the U.S. GM Training website, in Service Know-How streaming videos (fig. 1). Here are some highlights.

Inflation

TIP: This is good information to share with owners.

Tire inflation is the single most important, and most often overlooked, part of tire care. Operating a vehicle with just one tire underinflated by 20% (approximately 8 psi or 15 kPa) can reduce that tire's life by more than 9300 miles (15000 km) and can increase fuel consumption by 4%. With today's emphasis on fuel economy, this is a worthwhile tip.

Owners should check tire pressure at least once per month, when the tires are cold (driven less than 3 miles). They should be encouraged to observe the tire placard label, usually located on the driver door edge. It displays the Maximum Vehicle Capacity Weight, the Original Equipment Tire Size and the cold inflation pressures for front, rear and spare tires.

TIP: The inflation pressure specification embossed on the sidewall of the tire is the MAXIMUM operating pressure, which is not necessarily the right inflation pressure for the vehicle.

TIP: Air pressure in a tire varies according to the outside temperature and the speed and distance the vehicle has been driven. Typically tire pressure increases about 1 psi (7 kPa) as temperature increases 10° F (6° C).

Tire Pressure Monitoring System

In accordance with Federal regulations, all 2008 GM vehicles sold in the US are equipped with a tire pressure monitoring system. While some earlier TPM systems calculated tire pressure using wheel speed signals from the ABS system, the currrent TPM system uses a direct-measuring sensor in each wheel. Each sensor has a unique ID code that is transmitted along with pressure data.

A warning symbol is displayed when pressure in any tire drops to or below 75% of the recommended pressure. On many vehicles, the DIC displays actual tire pressure readings for added convenience.

TIP: Due to the temperature/pressure relationship explained earlier, if the TPM indicates low pressure on a cold tire, and turns off when the tire warms up, the pressure is marginal and needs to be inflated to the placard specification.

Bulletin 07-03-16-004A, revised in June 2008, provides an overview of TPM system operation, along with some informational Frequently Asked Questions.

Be sure your customers know how to interpret the tire pressure light. The light remains on solid to indicate a low tire pressure condition. The light blinks for about a minute and a Service Tire Monitor message displays when a malfunction occurs.

TIP: It is not necesary to perform sensor learning when the problem is resolved simply by correcting tire pressure.

TIP: TPM sensors are not compatible with commercially-available tire sealants. However, they have been tested with and are compatible with GM inflator kits and the sealants they use.

Tire Rotation

The importance of tire rotation is emphasized in the Owner Manual. Generally, the rule of thumb is to rotate tires every 5,000-8,000 miles (8000-13000 km), or whenever uneven wear is noticed.

On vehicles with a compact spare, a 4-wheel rotation scheme is required.

On front-wheel and all-wheel drive vehicles, move the front wheels straight back to the rear, and cross the rear wheels from side to side while moving them to the front.

On rear-wheel drive vehicles, move the rear wheels straight forward, and cross the front wheels from side to side while moving them to the rear.

TIP: Check tire pressures and correct as necessary after rotation.

TIP: After rotation, it is necesary to relearn the tire pressure wheel positions using the pressure-change method or the J-46079 tool. See SI for details.

IMPORTANT: Be sure to torque every lug nut to specification following the recommended sequence.

- Thanks to Dick Gratz

With Tire Pressure Monitor systems (TPM) being installed on nearly all new vehicles, here are some timely service and care tips. Follow the proper procedures when handling these sensors.

Damage

Analysis of returned sensors indicates physical damage due to improper installation,
over- or under-torque of the valve core, and damage to the schrader stem from inflation
air chucks or when using tire changers (fig. 2).

A TPM sensor may need to be replaced for multiple reasons: wheel replacement, faulty sensor, faulty schrader valve, or valve damage.

When removing a sensor from a wheel assembly, make certain that the threads of the stem are in good condition.

Inspect the stem for cracks or any indication of a bend, as this could cause a leaking valve.

When removing the valve stem core, use the proper core removal tool.

When installing a TPM sensor, it is critical to use the correct installation torque for the valve stem. A stem or core can be damaged both by over- or under-torquing. Calibrated torque wrenches are available for both the stem nut and the valve core.

The TPMS Service Tool Kit JSP-96254 (fig. 3) is available through the GM Tech Tools program. 1.800.GMTOOLS (1.800.468.6657) or www.gmtechtool.com. The valve stem torque wrench (fig. 4) is included in the kit. The valve core torque wrench LIS-18810 (fig. 5) is included in the kit and is also available separately.

Over-torquing the core, using a convenional core wrench, can crack the stem housing, which compromises the seal and creates a leaking stem.

The GM torque specification for valve cores is 4 in lb (0.45 Nm). This torque ensures that the core has seated properly in the stem and is properly sealed, without being over-torqued.

It is also important to avoid applying lateral pressure to the head of the valve stem with the air chuck while inflating tires. Excessive lateral pressure can cause the stem to crack or break off, or cause the core to become damaged and begin to leak (fig. 6).

Be extra careful because these stems are made of aluminum and are fastened solidly to the wheel. They are not as flexible as a regular rubber valve stem and cannot absorb the lateral pressure.

Excessive pressure can also be caused by a tire changing event were the changer mount head or tire lever strikes the valve stem.

- Thanks to Will Godfrey and Terry Goll

As part of an ongoing quality improvement effort, and to reduce the number of navigation radios returned to the Warranty Parts Center with "no trouble found," all navigation radios will go on parts restriction through the Product Quality Center (PQC) indefinitely.
This restriction is planned to begin September 2.

Dealers are at present required to call the PQC for all engine, transmission, and transfer case assembly replacements. This requirement is being extended to include navigation radios.

TIP: The restriction applies only to vehicles under warranty.

With the part restriction in place, a navigation radio can no longer be ordered directly from the Electronic Service Center (ESC). Instead, the dealer must complete a short part-number-specific questionnaire and then contact the PQC if they still feel a radio is needed. Based on the information provided, the PQC may direct the technician to published service information which could prevent unnecessary navigation radio replacements. After the necessary diagnostics have been performed, should a navigation radio still be required,
the PQC will order it from the ESC for the dealer.

A service bulletin is being developed which will include copies of the questionnaires.
Using the questionnaires and following the published service information will help make this process as efficient and painless as possible.

The restriction will affect the way dealers presently handle customers with radio concerns. So, all dealer service personnel need to be aware that PQC must be contacted before a navigation radio can be ordered. The technician may need more information regarding the concern than service advisors typically ask the customer. The dealer may also need to keep the vehicle longer for further diagnosis.

- Thanks to Diana Sancya

Beginning with the 2009 model year, several changes are being made in the way terminology is used in SI and in bulletins.

DEFINITIONS OF TERMS

Danger -- When encountering a DANGER, you will be asked to take a necessary action or not to take a prohibited action. If a DANGER is not heeded, the following consequences may occur:

- Serious bodily injury or death to the technician

- Serious bodily injury or death to other technicians in the workplace area

Warning -- When encountering a WARNING, you will be asked to take a necessary action or not to take a prohibited action. If a WARNING is not heeded, the following consequences may occur:

- Serious bodily injury to the technician

- Serious bodily injury to other technicians in the workplace area

- Serious bodily injury to the driver and/or passenger(s) of the vehicle, if the vehicle has been improperly repaired

Caution -- CAUTIONS call special attention to a necessary action or to a prohibited action.
If a CAUTION is not heeded, the following consequences may occur:

- Damage to the vehicle

- Unnecessary vehicle repairs

- Unnecessary component replacement

- Improper operation or performance of the system or component under repair

- Damage to any systems or components which are dependent upon the proper operation of the system or component under repair

- Improper operation or performance of any systems or components which are dependent upon the proper operation or performance of the system or component under repair

- Damage to fasteners, basic tools, or special tools

- The leakage of coolant, lubricant, or other vital fluids

Note -- NOTE statements emphasize a necessary characteristic of a diagnostic or repair procedure. NOTE statements are designed to do the following:

- Clarify a procedure

- Present additional information for accomplishing a procedure

- Give insight into the reason or reasons for performing a procedure in the manner recommended

- Present information that will help to accomplish a procedure in a more effective manner

- Present information that gives the technician the benefit of past experience in accomplishing a procedure with greater ease

- Thanks to Jerry Garfield

Owners of a 2007-08 Acadia and Outlook or 2008 Enclave may comment on a growl and/or whine type noise when the A/C compressor is engaged. The noise occurs while running at lower engine speeds, usually 1000-2000 RPM and is usually noticed during parking lot maneuvers. The noise will stop immediately when the compressor is disengaged.

Bulletin 07-01-39-005A provides A/C low pressure hose p/n 20757021 and repair information for this concern as well as instructions on how to provide feedback to the engineering team if necessary.

- Thanks to Doug Daugherty

3.1L (LG8) and 3.4L (LA1) Engines

There have been numerous reports of rocker arm attaching bolts coming loose or pulling out of the threaded holes in aluminum cylinder heads on the 60 degree V6 engines listed above. Inspection of returned cylinder heads and rocker arm attaching bolts has shown
that the threads in the holes had been damaged before the bolts loosened or pulled out.
The cause of the damage has been traced to the rocker arm bolts having been over-tightened. Further research of each vehicle’s service history (both warranty and non-warranty repairs) has revealed that in every case, the vehicle had prior engine repairs that required removal of the rocker arm bolts (e.g., replacing the lower intake manifold gasket).

Discussions with technicians at several GM dealerships has revealed that when reinstalling the rocker arm attaching bolts, technicians often use pneumatic (air) tools in an effort to save time. The bolt torque is determined by the shop air pressure, the adjustment setting
on the pneumatic tool and in many cases the maximum torque capability of the tool.

The tightening (torque) specification of the rocker arm attaching bolt and the method for tightening varies with engine and model year. However, in no case does the torque specification of the rocker arm attaching bolt exceed 32 Nm (24 lb ft). Tests conducted using a calibrated dial torque wrench show that the threads in the aluminum cylinder head will begin to fracture and start to strip when as little as 44 Nm (32 lb ft) is achieved. Once the threads have been fractured or stripped, it is only a matter of engine run time before the rocker arm bolt begins to loosen.

TIP: If one rocker arm bolt has loosened or pulled out, it is very possible that the other rocker arm bolts were over-tightened at the same time and those bolts could begin to do
the same, one at a time, in the future. It is suggested that the torque of all other rocker arm bolts be checked to see if they have been over-tightened and possibly stripped.

Method for Repairing a Damaged Threaded Hole

General purpose thread repair kits are available commercially. Refer to the thread repair kit manufacturer's instructions regarding the size of the drill and the tap to use. Also see the Thread Repair information in the appropriate SI engine section.

Warranty Information

The cause of the bolts loosening or pulling out of the aluminum cylinder head threaded holes has been traced to over-tightening during a previous engine repair that involved removal of the rocker arm bolts. As a result, the cost associated with repairing the threaded hole(s) or if necessary replacing the cylinder head(s), is NOT covered by the vehicle’s Powertrain Warranty without prior approval from the Area Vehicle Manager (AVM). Contact your AVM before proceeding.

- Thanks to Jim Kelly

On a 2007-08 Escalade, Avalanche, Silverado, Suburban, Tahoe, Sierra, Yukon, Yukon Denali, Yukon XL, or Yukon Denali XL, the SIR lamp may be on with DTC B0012 and/or B0013 Symptom 02, 04, or 0E set in the SDM. This can be caused by a shorted or cut wire behind the driver's side air bag (fig. 7).

Remove the driver's side air bag and inspect the wire harness between the air bag and the SIR coil for chafed or cut wires. If the wiring is cut or chafed, replace the SIR coil, which includes the harness.

It is necessary to make sure the protective tubing (yellow sleeve) on the new harness is pushed all the way down to the SIR coil. This will ensure the wiring does not get cut or chafed again. Add electrical tape to the other end of the yellow protective tubing to hold it
in place (fig. 8).

- Thanks to Jim Will

On 2007-08 Escalade, Avalanche, Suburban, Tahoe, Yukon, a running change was made to the front bumper bar, Front End Inflatable Restraint Discriminating Sensors (EFS) and SDM system calibrations on 8/5/2007. Vehicles built before 8/5/2007 have the first design EFS and vehicles built after 8/5/2007 have the second design EFS.

If the first and second design EFSs are mixed, DTC B0083 or B0084 may set. Normal diagnostics will not identify the parts/software incompatibility. It is important to verify when the vehicle was built and install the correct EFS.

- Thanks to Jim Will

8.6-inch Rear Axle

In the 2009 model year, the ring gear bolt torque specification has been changed on the 8.6-inch rear axle manufactured by AAM. This axle is used in 1500 Series (Half-Ton) full-size pickups and utilities, 1500 Series full-size vans, Hummer H3, TrailBlazer and Envoy, and Saab 9-7x 4.2i and 5.3i (except Aero) with the 5.3L V8 engine and/or 20-inch wheels.

The ring gear bolt torque specification has been raised from 120 Nm (89 lb.ft.) to 130 Nm (96 lb.ft.). The specification was changed because the bolt now uses a different adhesive patch material, which can be identified by the blue color.

- Thanks to Rich Burrell

Some of the carbon fiber trim is not installed to the ZR1 at the assembly plant, to avoid shipping damage. The body side lower rear (rocker) moldings, front valance panels and rear wheel opening front flares must be installed at the dealership during new vehicle preparation.

IMPORTANT: Once the rocker moldings and valance are installed, the vehicle's ground clearance can be as little as 4 3/4 inches (12 cm). See the August 2008 TechLink for lifting tips.

When lifting the vehicle, be sure there is sufficient clearance between the lift arms and the rocker panels for installation of the moldings.

Carbon fiber is brittle and breaks if bent. Broken edges may be sharp.

Refer to the instruction sheets that accompany the loose parts for details. Here are some highlights.

Rear Wheel Flares

The rear wheel flares must be installed before installing the rocker moldings (fig. 9).

The rear wheels must be removed for access to the wheel housings. Before removing the wheels, it is important to install the foam rotor protectors on the rear brake ceramic rotors.

TIP: Protectors can be installed through the spokes of the wheel.

TIP: Rotor protectors are provided to each ZR1 owner. Dealers should acquire a set for use in servicing the vehicle.

With the rear wheels removed, follow the instruction sheet to complete the installation of the flares. It is necessary to drill holes for the attaching rivets. Follow instructions.

TIP: Four rivets included with the flares are needed for the next step, installing the rocker moldings.

Rocker Moldings

TIP: The wheel flares must be installed first.

It is necessary to drill holes for the attaching rivets (fig. 10). Follow instructions.

TIP: Due to the length of the rocker moldings, have an assistant help hold the moldings in place to avoid breakage.

When installing the provided rivets to the molding, the arms of the vehicle lift may interfere with installing some of the rivets. If so, skip these until the vehicle is lowered.

After the rocker moldings are installed, install the butyl patches to cover the rivets and protect the rear flanges of the moldings, as instructed.

Front Valance

The front valance is installed below the front fascia using the screws and u-nuts provided (fig. 11). Follow instructions to install the fasteners in the correct order.

- Thanks to Brad Thacher

This information applies to the 2008 Tahoe and Yukon Hybrid with RPO HP2.

TIP: For background information, refer to SI document 2039343, Brake System, Hydraulic, Assist, and Control Description and Operation.

The 2 Mode braking system is unlike most traditional hydraulic brake systems. For proper brake system performance, it is very important to follow exactly the brake bleeding procedure in SI document 1998764, Antilock Brake System Automated Bleed Procedure.

Air trapped in the brake system will cause performance problems and DTCs without the symptoms of a spongy or low brake pedal.

IMPORTANT: If you miss a step in the brake bleed procedure, you must start over at step 1 without exception.

Observe these additional tips to perform a successful brake bleed on the 2 Mode hybrid.

TIP: Install a battery charger on the vehicle to maintain battery voltage.

TIP: Use a pressure bleeder that is capable of delivering 30 psi (200 kPa) for the entire bleed procedure. Failure to provide a constant 30 psi (200 kPa) will cause air to be trapped in the brake system and may cause brake performance problems or DTCs to occur.

It is strongly suggested that you use a J-29532-A pressure bleeder or a diaphragm type (ball bleeder) pressure bleeder in order to perform the hybrid brake system bleed procedure. A replacement J-29532-A can be ordered from 1-800-GM-TOOLS.

Tool J-29532-A has been tested extensively on this application and has proven to provide the necessary pressure and volume of brake fluid. Vacuum bleeding and other brake bleeding tools are NOT acceptable for this procedure.

TIP: In step 37 of the brake bleed procedure (SI document 1998764), you are instructed to loosen one of the two intermediate brake line fittings. These lines at the master cylinder are identified in the document.

- Thanks to Paul Radzwilowicz

Owners of some 2007-08 Avalanche, Silverado and Sierra Crew Cab, Suburban, Tahoe, Yukon, Yukon Denali and XL vehicles may comment that the B pillar trim is pulled away from the door weather strip, which creates a gap (fig. 12).

Updated B pillar trim panels have been released to correct this concern.The new trim panels have an additional snap retainer to help secure the lower part of the panel.
Use the chart below to obtain the correct trim panel part number.

- Thanks to Jim Will

A new design air conditioning accessory drive belt was introduced on the LH8 small-block V8 engine in the 2008 Hummer H3 (fig. 13). Now, the application is being extended to additional engines for 2009.

 

Vehicle Line	Engine RPOs
C/K	LY2,  LY5, LH6, LC9, LMG, L76, L9H, LY6
G/H	LY2,  LMF, LY6
S/T	LH6, LS2
CTS-V	LSA
H2	L9H
H3	LH8

The stretchy belt resembles a rubber band -- it applies tension when it's pulled slightly beyond its relaxed length -- and it doesn't have a belt tensioner.

TIP: Refer to the July 2007 TechLink for full details.

How is the Stretchy Belt Serviced?

IMPORTANT: The stretchy belt must not be re-used. Always replace with a new belt.

Removal -- To remove the stretchy belt, simply cut it with a razor knife or cutting pliers.

Installation -- As implied by its name, the stretchy belt is installed by carefully stretching it over the flanges of the pulleys. Nothing has to be loosened, and there is no tensioner.
The belt is guided onto the pulley by the installation tool while the balancer is turned with
a breaker bar and socket.

TIP: The replacement stretchy belt is packaged with a disposable installation tool and an instruction sheet. One installation tool is used for the LSA engine (fig. 14), and a different one for all the other engines (fig. 15).

See the instruction sheet for details.

- Thanks to Calvin Williams and Ron Minoletti

This information applies to these Cadillac models: 2004-09 SRX, 2005-09 STS (except V Series), and 2004-07 CTS (except V Series).

The air cleaner (outlet side) cover can be difficult to reinstall in the proper position if it has been fully removed from the housing. It is possible to incorrectly (fig. 16) reassemble the cover to the housing without the cover seated properly at the hinge. The tabs must be correctly (fig. 17) aligned with the hinge slots in the (inlet side) housing.

A  Tabs

B  Hinge slots

TIP: When viewed from the top, there may not be a visual indication that the box is not properly sealed.

To reduce the risk of an improperly sealed air cleaner assembly, verify that the cover is seated correctly in the housing before reinstalling the cover bolts.

TIP: To inspect that cover is properly seated once the cover bolts have been torqued down, gently pull up on the cover/MAF Sensor adapter. This gives a positive indication that the tabs of the cover are seated in the hinge slots.

TIP: If just replacing the filter element, the air cleaner (outlet side) cover does NOT need to be completely removed from the housing. The cover will pivot to allow for removal and installation of the filter element.

- Thanks to Jonathan Johnson and Jeff Strausser

HOW THE SYSTEM WORKS

The main function of the Passenger Presence System (PPS) is to detect the presence of a properly seated occupant and determine whether to turn the right front passenger frontal airbag ON or OFF, based on the occupant's size and weight.

There are two components that make up the PPS. These are the module and sensing mat. They are part of the seat.

The module is mounted under the seat pan, and the sensing mat is assembled between the seat foam cushion and seat pan.

Pressure on the sensing mat is converted into an electrical signal that the module reads and determines the passenger's classification.

For additional information, a streaming video is available from the U.S. GM Training website. Click Web Video Library from the main menu, then Technical, and then keyword search Occupant. The course, 22048.40V -- Occupant Safety Systems, is at the top of the list. You can also call 1.800.393.4831 to order a copy of the video.

SERVICE PARTS

The system allows you to service each component separately (module and/or sensing mat).

Order the modules according to the vehicle trim type. There is one module for cloth seats, and another for leather seats.

TIP: These modules are not interchangeable.

The labor code is C8870.

DIAGNOSTIC TROUBLE CODES

DTC information for the PPS can be retrieved with the Tech 2 and displayed on the Tech 2 screen.

Generally, if the PPS has history codes only, the appropriate electrical tests and visual inspections must be conducted to ensure that there is no intermittent problem.

You may see a history DTC B0081 5a in some vehicles. The AOS is setting this DTC due to an issue with the messages in software for AOS and SDM. There is no need to replace parts for this DTC. Be sure the DTC is history when the key is in RUN. If the DTC is active, follow the SI instructions.

After installing any PPS components, the system needs to be re-zeroed using the Tech 2. This will update the empty seat reference values stored in the ECU and ensure proper system performance.

PROPER RE-ZEROING PROCEDURE

TIP: Ensure that the passenger seat is empty before initiating a re-zeroing command. Also check that there are no active DTCs in the PPS.

1. With the Tech 2, initiate a re-zeroing command.

2. If the system classifies the current seat condition as Empty, it will update the reference values.

3. After 20 seconds, cycle the ignition OFF to ON.

4. Verify that the re-zero is successful by sitting on the passenger seat and verifying that
the passenger airbag telltale light changes from OFF to ON. If the telltale does not change, follow SI instructions for DTCs.

TIP: A DTC B0081 11 will set to indicate that the re-zeroing process has failed.

IMPORTANT

1. If the system fails to re-zero, verify that the passenger seat is empty and no active DTCs exist. Then resend the zero command and follow the instructions above at least three times.

2. During the re-zeroing process, the seat must be empty of all objects and the clearance specified in SI must be observed.

3. Seat cushion heaters cannot be double stacked. Follow the SI instructions to replace the front passenger heater mat.

- Thanks to Esther Anderson, Sue Rashid and Joe Garcia