Transmission Downshifts During Normal Mode Powertrain Grade Braking

Mid-August 2015, Volume 17, No. 16 Transmission Downshifts During Normal Mode Powertrain Grade Braking Powertrain Grade Braking is a transmission feature on 2013-2015 Avalanche, Silverado, Suburban, Tahoe, Express, Savana, Sierra, Yukon models and Escalade models equipped with the 6L80 (RPO MYC) or 6L90 (RPO MYD) automatic transmission and 2015 Colorado and Canyon models equipped with the 6L50 (RPO MYB) automatic transmission that helps to maintain the desired speed when driving on a downhill grade. The system uses the engine and transmission to slow the vehicle by maintaining lower gears longer and increasing shift pressures. This helps reduce brake temperatures and wear on the braking system, saves fuel, and provides enhanced vehicle control. Because the transmission may downshift unexpectedly when Powertrain Grade Braking is active, some owners may have concerns about how the transmission operates. Starting with the 2013 model year, full-size trucks and utilities have had Powertrain Grade Braking while the transmission is in Normal mode is when Tow/Haul mode off. Powertrain Grade Braking has been available since 2009 on light-duty models and 2007 on heavy-duty models, but the Tow/Haul mode had to be selected. Powertrain Grade Braking should not be confused with Cruise Grade Braking. Powertrain Grade Braking Operation Normal Mode Powertrain Grade Braking defaults to ON at each ignition key cycle. To disable/enable all grade braking, press and hold the Tow/Haul button on the shift lever for three seconds. No grade braking is available in Range Selection Mode (Manual Shift Mode). Powertrain Grade Braking requires the driver to apply steady brake pedal pressure to maintain the desired speed while driving on a downhill grade. The vehicle's control modules monitor the amount of brake pedal continued on page 2 CONTENTS Techline News Automatic Java Updates and GM Service Applications TIS2Web uses the Java program to launch GM Service Applications such as SPS, GDS2 and MDI Manager. Java acts as a plug-in that assists the programming code with executing functions. Since Java is a program itself that is owned and managed by the company Oracle, updates to the Java program sent out by Oracle can affect the functionality of the GM Service Applications. Currently, the supported version of Java for the GM Service Applications is Java 7 Update 67. It s best to have only this version of Java installed. When Java updates, it leaves old versions on the machine that build up over time, which can eventually cause issues. continued on page 2 Transmission Downshifts during Normal Mode Powertrain Grade Braking... 1 Automatic Java Updates and GM Service Applications.... 1 Keep the Field Product Reports Coming.... 3 Obtaining a TAC or PQC Case.... 3 Low A/C Refrigerant Charge.... 4 Trailer Brake Control Switch Wiring.... 4 Aftermarket Navigation Systems... 4 Disconnected RCDLR Antenna Conditions.. 5 Customer Care and Aftersales

Transmission Downshifts during Normal Mode Powertrain Grade Braking continued from page 1 apply, vehicle deceleration rates, and other factors to determine if Normal Mode Powertrain Grade Braking is necessary. When the feature activates, the transmission downshifts and engine RPM increases. At this point, if the brake pedal is released, the transmission will hold the current gear. If the driver reapplies steady brake pedal pressure and additional engine/transmission braking is needed to help maintain the desired speed, additional downshifts may occur. Grade braking is exited the accelerator pedal is depressed. Normal Mode Powertrain Grade Braking has a less aggressive transmission downshift schedule than when in Tow/Haul mode. w Contact Driver Us button Information Center Messages There are several messages that will display in the Driver Information Center depending on the state of the Powertrain Grade Brake system. Grade Braking On message appears once. GRADE BRAKING DISABLED or GRADE BRAKING OFF displays when the system has been disabled with the Tow/Haul button. GRADE BRAKING ENABLED or GRADE BRAKING ON displays when the system has been enabled with the Tow/Haul button. GRADE BRAKING ON or GRADE BRAK- ING ACTIVE displays when the system activates for the first time in an ignition cycle while driving on a downhill grade. This message only appears the first time the system is activated and does not appear later when the system is activated again when driving on roads with many changing grades. Hill Descent Control Normal Mode Powertrain Grade Braking is not the same system as Hill Descent Control (HDC), which uses the braking system maintain vehicle speed on a very steep incline greater than or equal to a 10 percent grade. The HDC system must be turned on or off using the switch on the center stack. To enable HDC, vehicle speed must be below 37 mph (60 km/h). A blinking HDC light indicates that the system is actively applying the brakes to maintain vehicle speed. The system is automatically disabled if vehicle speed is above 50 mph (80 km/h) or above 37 mph (60 km/h) for at least 30 seconds. Thanks to Nick Champion Techline News Automatic Java Updates and GM Service Applications continued from page 1 Java is generally updated every three months. The default setting in the Java Control Panel is set to Automatically Update. This can be problematic if you wish to stay on one version of Java that is stable and compatible with your applications. The Java settings can be changed to disable the automatic updates. Click Java to open the Java control panel. Disabling Automatic Updates for Java Open the Windows start menu and click Control Panel. With the control panel in icon view (view by large icons or small icons), click the icon that says Java to open the Java control panel. Click the Update tab. Remove the check in the box next to Check for Updates Automatically. A pop-up window will display once the box for automatic updates has been deselected. Click the Do Not Check button in the pop-up window. Click the OK button and the change to disable automatic updates of Java will be saved. Thanks to Chris Henley Uncheck the Check for Updates Automatically box. Click the Do Not Check button. 2 Mid-August 2015

Keep the Field Product Reports Coming Dealership employees play a key role in reporting product issues using the Field Product Reporting process (in Canada, referred to as the Product Information Reporting process). The timeliness and detailed information in these reports are extremely important to the product problem resolution process. Field Product Reports can be helpful in communicating a number of conditions, such as wiring harness routing damage (submitted with photos), emerging repetitive repairs not addressed by a Bulletin or PI, or significant issues not covered under warranty (including conditions considered normal operation or found during PDI). Why are Field Product Reports Needed? Field Product Reports provide: Early identification of emerging issues (starting point) Provide direct feedback to GM Engineering on customer concerns Provide real-world examples to GM Engineering Allow GM Engineering to review concern and repair information directly from the dealership/service technician Provide feedback to GM plants on potential build issues The details in the Field Product Reports provided by first-hand observations from technicians help to collectively identify and address all types of emerging issues, including safety concerns, affecting new vehicles. This information is especially critical during the launch of new models. When considering if submitting a product report is necessary, determine if it meets the following three critical points: Critical Product Concern Safety concern, no start, walk-home condition (including vehicles towed to dealerships or involving leaking fluids) Critical Timing Safety concern, vehicle in dealership, plant build concern Critical Information More details, including photos or videos to better understand a condition TIP: Service Information, Bulletin information and Labor Time Guide issues should be addressed through Service Information Feedback, not a Field Product Report. Submitting a Field Product Report only takes a few minutes. Information in the report should include: Required information section: VIN (last 8 lookup or full VIN) Odometer Condition Cause Correction More Information expanded section: Job Card # TAC Case # Part # (numbers - provide scan) Photo (max number = 6) Video (max duration = 30 Seconds) Download the App to Make Submitting Field Product Reports Easier The Field Product Report application (U.S. dealerships only) makes it easy to create and submit a report. The GM Field Product Reporter app is free and can be found on the app stores for Android and Apple devices. To use the app, download it to your mobile device and log in using your GlobalConnect ID and password (user profile information must be filled out on the initial use), and then start filling out the required fields. You can also attach up to six photos or up to 30 seconds of video, including audio. After sending a report, all photos and videos will be deleted from the device. To save a copy of the report or send it to additional Download the app for addresses, add the Android and Apple addresses in the TO: devices. line on the top of the review screen. Email a Report In addition to the Field Product Report app, reports can still be submitted via email. Fill out the form located on GM GlobalConnect > Service Workbench > Service Forms and email it to electronicproductreport@ gm.com. In Canada, reports can be submitted online via the PIR Online app located in the Service Department page of GM GlobalConnect. For more information about when and how to submit a Field Product Report, refer to Bulletin #02-00-89-002O (U.S.) or Bulletin #10-00-89-006 (Canada). Thanks to Ray Romeo Fill out the condition, cause and correction information on the app. Obtaining a TAC or PQC Case GM dealership service managers who would like a copy of a GM Technical Assistance Center (TAC) or Parts Quality Center (PQC) case covering an issue at their dealership, can now request one through a new process at TAC. The formal process enhances the support being provided to dealerships by TAC. Dealership service management can request a TAC or PQC case in PDF format. To request a copy of a case: Send the formal request via e-mail from a GM dealership (non-personal) e-mail account to your District Manager of Aftersales (DMA) and copy GM TAC at tachelp@gm.com. Write TAC/PQC Case Request DMA Approval Required in the e-mail Subject line. Include the dealership s BAC, the VIN, TAC/PQC case number as well as your name, dealership position, and contact number at the dealership in the e-mail message. If the DMA determines there is a true internal GM dealership business need for this request (i.e., case copy not to be provided to non-dealership personnel), the DMA will need to respond to GM TAC and the GM dealership with their approval before GM TAC will provide a copy of the TAC or PQC case. Once approved, an email with a PDF of the case will be sent to the requesting GM dealership. In Canada, follow these steps and e-mail your District Manager Customer Care and Service Process (DM-CCSP) and copy GM Canada TAC at techservice.canada@gm.com. Thanks to Cary Vernier Mid-August 2015 3

Low A/C Refrigerant Charge Some 2013-2016 Traverse, Enclave, and Acadia models may have warm air conditioning. A check of the refrigerant level may reveal a very low/empty charge. After performing normal diagnostics, if the source of the refrigerant leak is not found, check for a small refrigerant leak at the rear auxiliary air conditioning evaporator. Engineering has determined that dust from the blower motor brush on the evaporator may have some copper particles in it, which causes accelerated corrosion to the evaporator. The copper particles are coming from the blower motor during the motor breakin period, so the motor does not need to be replaced. Remove the rear auxiliary blower control module and insert the GE 50078 Electronic Leak Detector to test for a leak. If a leak is found, replace the rear evaporator. Also remove the rear blower motor and blow the fan and blower cage with compressed air to remove any copper particles and dust that could be redeposited on the new evaporator. This will prevent the possibility of a subsequent failure of the evaporator from the copper dust remaining on the blower fan cage. Thanks to Jim Miller Trailer Brake Control Switch Wiring An intermittent Service Trailer Brake message may be displayed on the Driver Information Center of some 2014 Silverado 1500 and Sierra 1500 models and 2015 Silverado and Sierra models. DTCs C1115 (Manual Trailer Brake Apply Request Switch Signal), C1116 (Manual Trailer Brake Apply Request Signal 1), C1117 (Manual Trailer Brake Apply Request Signal 2) and/or C1118 (Trailer Brake Control Sensitivity Switch Circuit) may be set in the Chassis Control Module. The trailer brake control system has a control panel with trailer gain and manual apply switches. The control panel switches allow the driver to adjust the amount of output, referred to as trailer gain, available to the electric trailer brakes and to manually apply the trailer brakes. Use GDS to view the following Trailer Brake Control Switch parameters in the Chassis Control Module: Manual Trailer Brake Apply Request Signal 1 Manual Trailer Brake Apply Request Signal 2 Trailer Brake User Gain Switch The normal working ranges for the Trailer Brake Control Switch parameters are: Manual Apply Slide Lever Fully Applied Signal 1 89% (+/- 5%) Signal 2 11% (+/- 5%) Manual Apply Slide Lever Fully Released Signal 1 11% (+/- 5%) Signal 2 89% (+/- 5%) User Gain Switch Switch at rest 89% (+/- 5%) + switch pressed 37% (+/- 5%) switch pressed 23% (+/- 5%) In most cases, the Chassis Control Module is not the cause of the DTCs and there is either a concern with the wiring to the trailer brake control switch or the switch itself. Trailer brake control panel The wiring between the Chassis Control Module and trailer brake control switch passes through in-line connector X185 or X138 (depending on vehicle build; refer to the Service Information), as well as the X1 and X5 connectors of the X61A Junction Block-I/P. Inspect the wiring from the Chassis Control Module to the trailer brake control switch. Check the connectors for any backed out, loose, or poor tension terminal/connector issues. Check the wiring between the Chassis Control Module and the trailer brake control switch. If no wiring issues are found, check the trailer brake control switch. The trailer brake control switch parameters can be monitored with GDS while wiggling the circuits/harness between the Chassis Control Module and switch. Look for the values to change. Thanks to Jim Will Aftermarket Navigation Systems Many aftermarket companies advertise modules that are designed to upgrade a non-navigation infotainment system to a navigation-enabled system on vehicles equipped with Chevrolet MyLink, GMC or Buick IntelliLink or Cadillac CUE infotainment systems. In many cases, the aftermarket module replaces the OEM Human Machine Interface (HMI) module. The aftermarket modules are marketed as a replacement HMI module that contains the navigation software necessary to run the navigation system. The modules replace the existing HMI module and use the factory wiring harness and bolt locations. These components are not supported by GM in any way and are not approved as an accessory that is compatible with any GM infotainment system. If an aftermarket HMI module is installed, it can cause various other issues that affect the proper operation of several systems. For example, the aftermarket module may cause the Rear Vision Camera to not work properly. Or if a technician attempts to reprogram an aftermarket module, it may not accept the programming and fail, causing irreparable damaged to the module, because it s not the correct HMI module for the vehicle calibration. Verify the Part Number If it s suspected that an aftermarket module it installed in a vehicle, verify the part number with the correct part number for the appropriate model year in the electronic parts catalog. Thanks to Mike Magyar 4 Mid-August 2015

Disconnected RCDLR Antenna Conditions Some 2015 Escalade models, Suburban, Tahoe, and Yukon models may have DTCs for any of the tire sensors C0750 (Left Front Tire Pressure Sensor), C0755 (Right Front Tire Pressure Sensor), C0760 (Left Rear Tire Pressure Sensor), and/or C0765 (Right Rear Tire Pressure Sensor) set in the BCM. Other conditions may include: One or more tire pressures displaying dashes on the Driver Information Center (DIC) Service Tire Monitor System message displayed Poor range or an inoperative Remote Keyless Entry (RKE) transmitter No Fob Detected message displayed or inoperative passive entry system (if equipped) These conditions may be caused by a poor or disconnected antenna connection. The Remote Control Door Lock Receiver (RCDLR) antenna system consists of the four components: RCDLR, coax cable, Antenna Amplifier Module, and an antenna (located in right rear quarter glass). Before any components are replaced for these conditions, check for any disconnections in the RCDLR antenna system. The closer the disconnection is to the RCDLR, the greater the number of symptoms that will be noticed. Here are several examples. If the Antenna Amplifier Module is disconnected from the antenna at right rear quarter glass, there may be little to no noticeable issues, but the RKE range may be a little shorter than a similar vehicle. If the coax cable is disconnected at the Antenna Amplifier Module, the RCDLR may have intermittent issues receiving signals from the Tire Pressure Monitor (TPM) sensors that are farthest from the RCDLR (LF, LR, RF tires). The DIC may display a Service Tire Monitor System message and dashes for these tire pressures. In most cases, the signal from the right rear tire sensor, which is the closest to the RCDLR, will not have any issues. The RKE will have a shorter range. If the coax cable is disconnected at the RCDLR, the RCDLR may not receive any TPM sensor signals. The Service Tire Monitor System message and the tire pressures will show dashes in the DIC. The RKE system may work when the transmitter is inside the truck or just outside the truck. There may be Passive Entry/Passive Start conditions such as a No Fob Detected message or Passive Entry being inoperative. If the transmitter is placed into the transmitter pocket, the vehicle will start. Thanks to Jim Will There are three locations where the RCDLR antenna system can become disconnected: Antenna Amplifier Module (#3) disconnected from the antenna at the right rear quarter glass (#4) Coax cable (#2) disconnected at the Antenna Amplifier Module (#3) Coax cable (#2) disconnected at the RCDLR (#1) GM TechLink is published for all GM retail technicians and service consultants to provide timely information to help increase knowledge 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: * TechLink PO Box 500 Troy, 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. Mid-August 2015 5