CONTENTS

New Bulletin Numbering System for North America . . . . . . . . . . . . . . . . . . . 1

Take the 2015 TechLink Reader Survey . . 1

Share Your Comments on GM Service Information . . . . . . . . . . . . . . . 2

Ambient and HVAC Temperature Display Conditions . . . . . . . . . . . . . . . . . . . 3

Preventing Overhead Entertainment Display Damage . . . . . . . . . . . . . . . . . . . . 3

Aftermarket Equipment Connected to Multi-Media Ports . . . . . . . . . . . . . . . . . 3

Supercharger Noise Diagnosis . . . . . . . . . 4

Hand-Free Liftgate Operation . . . . . . . . . . 5

Customer Care and Aftersales

Mid-October 2015, Volume 17, No. 20

Techline News

At TechLink, our goal is to provide the latest GM technical news and repair information to help you quickly and accurately repair the vehicles that come into your service department every day .

We cover a wide range of topics, from the latest diagnostic and technical repair information to Techline programming, new model features, special tools and more .

We would like to hear from technicians and other service department professionals about the types of repair information to cover as well as get your thoughts on how we’re doing . Your input

will help in determining the coverage of future editions . So which topics are of interest and value to you?

Click the Survey link on the right side of the TechLink home page to take a short survey about the information you want most in TechLink . The survey will be available until the end of October .

Your input is very important to us . Thanks for taking the time to complete the survey . We’ll share the results when the survey is complete .

Thanks to Lisa Scott

What Do You Think? Take the 2015 TechLink Reader Survey

New Bulletin Numbering System for North AmericaPerform a Service Bulletin search for a 2015 GM model in the Service Information and you may notice that the bulletin numbers in the search results look a little different . You’ll see a bulletin number such as #15-NA-03 as well as more familiar looking numbers such as #15-06-03-001A . Recently, GM changed the bulletin numbering system for all new bulletins going forward in order to commonize the system with other GM regions .

Here’s what the new numbering system means .

• The first two places specify the calendar year in which the bulletin was authored . 15 indicates the 2015 calendar year .

• The third and fourth places designate the region where the bulletin was authored . Bulletins that are written in North America have a region code of NA .

• The last three places are the sequencing code . Each region uses their own sequence number .

If a Service Bulletin is revised for any reason, its number will remain the same . There will no longer be a letter after the bulletin number . Instead, a version

continued on page 2

2 Mid-October 2015

New Bulletin Numbering System for North Americacontinued from page 1

number will be added at the bottom of the bulletin along with a statement explaining what was modified .

TIP: The new Service Bulletin numbering system only af-fects 2015 calendar year and later bulletins . Older bulletins will not be updated with the new numbering system .

In addition to the bulletin number, the format of the bulletin it-self has changed . The models affected by the bulletin are now listed in a table, broken down by Brand, Model, Model Year, VIN, Engine and Transmission . The table format makes it easy to quickly identify the models and components involved .

Additional information that may be included in the new bul-letins cover the Condition, Production, Correction, Service Procedure, Parts Information, Warranty Information, Version and Bulletin Modification .

Thanks to Ed Laskowski

Share Your Comments on GM Service InformationThe goal of the daily-updated GM Service Information is to provide technicians with the information they need to quickly and accurately service GM vehicles . By tak-ing a moment to submit feedback on the Service Information, your comments help ensure the application is user-friendly, working properly, and that the information is correct .

The Service Information now includes much more than Service Manuals, Bulletins and Unit Repair Manuals . Depending on the model, other vehicle publications may in-clude Accessories Manuals, Labor Time Guides, Owner Manuals and Supplements, and Pre-Delivery Inspection Forms .

Click the Mailbox Icon

There are several ways to access the Service Information feedback form .

1 . On the Service Information home page, click the “Send us your feedback” link next to the mailbox icon under the list of options .

2 . Once a vehicle is built, each menu page has a feedback link in the upper right cor-ner of the page . It’s the same mailbox icon . Click the icon to open the feedback form .

3 . Or on every document in the Service Information, the same feedback link (mailbox icon) can be found in the upper right corner .

TIP: When in a service document, the feedback form covers Service Information issues . However, when in a Labor Time document, a more comprehensive feedback form is provided to request a labor time review .

Feedback Form Details

In the feedback form, fill in all of the fields under Dealer Information, To Submit a Problem or To Submit a Suggestion . An asterisk indicates all required fields .

TIP: Be sure to include an email address and phone number . The Service Information team may want to contact you to gather additional information or reply to your feed-back with a response .

To submit a problem, fill in the requested information . Be as thorough as you can be when giving a detailed description of the problem . Explain exactly what happened and if the problem could be reproduced . Be sure to include the vehicle type and document ID if available .

If you have already built a vehicle, and are looking at a service document when you click the feedback button, the feedback form will automatically fill in the vehicle you're working on and the document ID number .

To submit a suggestion, fill in the box provided using your own words to give a detailed description of your suggestion for any improvements you would like to see .

Once you have submitted your feedback, a confirmation screen will appear to let you know your submission has been sent .

Thanks to Lisa Scott

GM bulletin global numbering example

Look for the Feedback link with the mailbox icon.

Click the Feedback link on the home page.

Click the link in the upper right corner when viewing a document.

Provide all the details in the feedback form.

Mid-October 2015 3

On some 2012-2016 Verano, 2013-2015 Malibu, and 2016 Chevrolet Malibu Limited models, the driver and passenger HVAC tem-perature settings may be displayed in Celsius or the outside ambient tempera-ture may be missing from the radio/HVAC (or info-tainment) display . These conditions may be caused by the outside ambient temperature sensor being disconnected or the wiring having a fault .

Check the Instrument Panel Cluster for any DTCs . If DTC B0158 (Ambient Air Temperature Sensor Circuit) is set, check that the outside ambient temperature sen-sor is connected .

If the sensor is connected, check the integrity of circuits 61 and 636 from the sensor to the Instru-ment Panel Cluster . If the wiring is secure, follow the diagnostic instructions for DTC B0158 in the appropriate Service Information .

Thanks to Christopher Crumb

The Warranty Parts Center has received several overhead entertainment displays from 2014-2015 Escalade, SRX; 2015 Silverado, Suburban, Tahoe, Sierra, and Yukon models, equipped with the Rear Seat Entertainment Package (RPO U42), with the LVDS (Low Voltage Differential Signaling) cable connector broken off of the display .

To prevent this damage, do not let the weight of the display hang from the LVDS cable when removing an overhead video display . Instead, sup-port the display and disconnect the LVDS cable to avoid damage to the connector or circuit board .

Thanks to Ryan Dorland

Various infotainment conditions caused by aftermarket equipment connected to the multi-media, USB or auxiliary input ports may be found on some 2013-2015 ATS, CTS, SRX, and XTS models equipped with the CUE system; 2014-2015 Regal and LaCrosse models equipped with the IntelliLink system; 2014-2015 Canyon, Sierra, and Yukon models equipped with the IntelliLink system; and 2014-2015 Colorado, Corvette, Impala, Silverado, Suburban, and Tahoe models equipped with the MyLink system .

The infotainment conditions may include blank displays, flashing displays, error or update failed messages, the navigation map not loading, or Bluetooth or USB concerns . If any of these conditions are present, check for any devices plugged into the USB ports, SD card slots, or 12 volt accessory ports . SD cards mount almost flush to the port and can be difficult to see . Remove the devices prior to diagnosing any infotainment concern .

Many vehicles also have a USB port that can only be accessed by raising or lower-ing the radio display/control assembly . Verify there are not any devices in the stor-age bins behind the display/control assemblies, if applicable

Thanks to Ryan Dorland

Ambient and HVAC Temperature Display Conditions

Preventing Overhead Entertainment Display Damage

Aftermarket Equipment Connected to Multi-Media Ports

The temperature settings may be in Celsius or the ambient temperature display may be missing.

Check for any devices plugged into the USB ports and other ports.

Circuits 61 and 636

Damage to the circuit board.

4 Mid-October 2015

Supercharger Noise DiagnosisThe supercharger on the 6 .2L V8 engine (RPO LT4) of the 2015-2016 Corvette Z06 and 2016 CTS-V produces distinct sounds at different engine RPMs .

The sound of the supercharger is different than other various engine noises, such as the high-pressure fuel pump, vacuum pump, valve train or transmission flexplate .

Click the LT4 engine to listen to the normal sound of the super-charger for reference in determining the origin of an engine noise .

A normal amount of rattle/rumble noise can be heard along with a high-pitched noise that sounds like a generator electrical noise . The rattle/rumble sound also changes with temperature (it’s more no-ticeable on a warm engine) .

Supercharger Operation

The Roots-type supercharger on the LT4 engine is a positive displacement pump that consists of two counter-rotating rotors installed into the lower intake manifold housing . The rotors are designed with four lobes and a helical twist . The rotors of the super-charger are designed to run at a minimal clearance, not in contact

with each other or the housing, and are timed to each other by a pair of precision spur gears that are pressed onto the rotor shafts . The rotors are supported at each end by self-lubricating, non-serviceable bearings . The drive belt pulley is pressed onto the input shaft . The input shaft is coupled to the rotor shaft . Both the belt pulley and shaft coupling are non-serviceable .

The supercharger is designed to increase the air pressure and density in the intake manifold . When this air is mixed with the cor-rect amount of fuel the result is more power from the engine . This excess air creates a boost pressure in the intake manifold with a maximum engine boost of 66 .9 kPa (9 .7 psi) . Because the super-charger is a positive displacement pump and is directly driven from the engine drive belt system, boost pressure is available at all driving conditions .

Supercharger Sounds

Here are some typical sounds that are generated by the super-charger .

Whine:

• Whine noise is typical of all superchargers and is not a reason to replace the supercharger or other components .

• Supercharger whine, inherent to the Roots design, results from eight pulses per engine revolution, 2:1 drive ratio x 4 lobes . The air induction system structure and acoustic resonators are de-signed to minimize whine .

Whistle:

• A whistle noise is generated by tooth contact of the spur gears between the rotors . For instance, a low level whistle may occur at 2,300–2,800 RPM at 80 percent load driving up a very long grade . Although most of these conditions are addressed by sound path isolation to the passenger compartment, some can still be heard by a very critical ear .

Supercharger Rattle or Growl:

• Supercharger growl may be heard at low speed or idle, with the engine under light load .

• Minuscule crankshaft speed variations, influenced by the torque converter, transmission, drive shaft, differential, and tires, are transmitted through the flexible drive belt to the supercharger . Operating in very thin air, the rotors oscillate and cause the load to alternate from the drive to driven sides of the gear teeth . The entire supercharger drive system is tuned to minimize this noise .

Internal Isolator Rattle:

• The supercharger’s internal isolator between the pulley and the rotor shaft is designed to minimize a knocking sound when the engine is turned off and the mass of the supercharger rotor set is suddenly jerked to a stop, and it is tuned to minimize the normal engine firing pulses passed on to the supercharger rotor drive gears . It is active only in an unloaded condition, low engine speed point where boost is not requested .

• If the engine or one of the components in the driveline is not operating to design intent, the isolator may make a harsh, inter-mittent rattle sound that often goes through cycles as the engine speed or other conditions change slightly .

Thanks to Tracy Lucas

Supercharged 6.2L V8 (RPO LT4)

The LT4 engine features a Roots-type supercharger.

Mid-October 2015 5

GM TechLink is published for all GM retail technicians and service consultants to provide timely information to help increase know-ledge about GM products and improve the performance of the service department .

Publisher:John Meade GM Customer Care and Aftersales

Editor:Lisa G. Scott GM Customer Care and Aftersales

Technical Editor:Mark Spencer /mspencer@gpstrategies .com

Production Manager:Marie Meredith

Graphic Design:5by5 Design LLC/dkelly@5by5dzign .com

Fax number: 3 1-248-729-4704

Write to: * TechLinkPO Box 500Troy, MI 48007-0500

GM TechLink on the Web: : GM GlobalConnect

General Motors service tips are intended for use by professional technicians, not a “do-it-yourselfer .” T hey are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely . If a condition is described, do not assume that the information applies to your vehicle or that your vehicle will have that condition . See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information .Inclusion in this publication is not necessarily an endorsement of the individual or the company .

Copyright© 2015 General Motors All rights reserved .

Hands-Free Liftgate OperationThe hands-free activation of the power liftgate may be temporarily disabled under some conditions on 2015-2016 Escalade models, Suburban, Tahoe and Yukon models equipped with the Hands-Free Power Liftgate (RPO TC2) .

For example, after several hands-free opening and closing events in a row, the power liftgate may be disabled . If the liftgate does not respond to the hands-free kick motion, open and close the liftgate by another method, such as using the power liftgate button on the overhead console or Remote Keyless Entry (RKE) trans-mitter (key fob), or start the vehicle and the hands-free feature will be re-enabled .

Here are a few tips covering the proper operation of the hands-free liftgate feature .

Key Fob Range – The RKE key fob must be within the detection area of 3 feet (1 m) of the rear bumper .

Kick Zone – Hands-free operation will work best when the foot kick is conducted at the direct center or left of center of the kick zone below the rear bumper .

Foot Kick Motion – The proper foot kick motion is slightly different between short and long wheelbase models .

For short wheelbase models (Tahoe, Yukon, and Escalade), kick your foot parallel to the ground in one swift motion underneath the center of the rear bumper, and then pull it back .

For long wheelbase models (Subur-ban, Yukon XL, Escalade ESV), kick your foot straight up in one swift motion under the center of the rear bumper, and then pull it back .

On all models, do not sweep your foot from side-to-side, keep your foot under the bumper, or touch the lift-gate until it stops moving .

The liftgate may open or close if clean-ing or working near the rear bumper, splashing water, or stepping into the liftgate opening . To avoid inadvertent operation, keep the RKE key fob away from the rear bumper detection area or turn the power liftgate mode switch to Off .

Thanks to Jim Will

Hands-free power liftgate

Kick zone location under the rear bumper

On short wheelbase models, kick your foot parallel to the ground under the bumper.

On long wheelbase models, kick your foot straight up under the bumper.