TECHLINEnews. The New 2012 Sonic. SI Screen Characters. Powertrains. Contents

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1 August 2011 Volume 13, No.8 The New 2012 Sonic The 2012 Chevrolet Sonic will be arriving in dealerships soon as a replacement for the Aveo. It s an all-new entry in the sub-compact market. The Sonic will be offered in two body styles a four-door sedan and a five-door hatchback. Powertrains Both Sonic models are powered by efficient Ecotec 4-cylinder engines a standard 1.8L engine and an optional 1.4L turbo engine the same engines used in the new Cruze. continued on page 2 TECHLINEnews SI Screen Characters Service Information (SI) users may notice improperly formatted screen characters when viewing diagnostic repair procedures. Screen character issues may be present when using either Internet Explorer (IE) 7 or 8. This issue may cause screens to appear incomplete or confusing. Review #PI0135A for some screen comparisons to determine if your PC exhibits these symptoms using either versions of Internet Explorer. Adjusting the settings in Windows or the browser will enable the information to be displayed properly. At this time, General Motors does not recommend the use of Internet Explorer 9. Techline applications will require some changes in order to support IE 9. An announcement will be sent to dealerships when IE 9 is compatible with Techline software. To view the GM Service Infrastructure Guidelines for the latest hardware and software requirements, go to the website and select the tab to "Techline IT Solutions" and the link "GM IT Standards." Dealers in Canada should refer to the GM Canada Dealer Infrastructure Guidelines in the Service Library of GlobalConnect. Thanks to Lisa Scott Contents The New 2012 Sonic SI Screen Characters SRX Reprogramming Updates Compress Natural Gas Fuel Systems Training Two-Mode Hybrid Electronic Brake Control Module DTCs Brake Pad Wear and Fit Coolant Leak from HVAC System Intermittent No Start Condition and Illuminated MIL Air Trapped in Brake System Insufficient Windshield Washer Spray Instant Update of the Ambient Temperature Sensor Inoperative Fuel Gauge Sunroof Sunshade Relearn Inside Rear View Mirror Automatic Day-Night Feature Fog Lamp Operation Service Know-How Car Issues Fix It Right the First Time Truck Issues Fix It Right the First Time....9 Customer Care and Aftersales

2 The New 2012 Sonic continued from page 1 The standard Ecotec 1.8L 4-cylinder engine is paired with the M26 five-speed manual transmission or the Hydra-Matic 6T30 sixspeed automatic transmission. The naturally aspirated 1.8L engine generates an estimated 135 horsepower along with 125 lb.-ft. of torque at 3,800 rpm and features a hollow-frame cast-iron cylinder block and dual overhead camshafts with variable valve 1.8L 4-cylinder engine timing for durability and efficiency. Its two-stage variable intake manifold allows approximately 90 percent of peak torque to be available from 2,400 rpm to 6,500 rpm. A sportier option is the available Ecotec 1.4L turbocharged engine with the M32 six-speed manual transmission. The 1.4L turbo engine is rated at an estimated 138 horsepower and 148 lb.-ft. of torque between 1,850 rpm and 4,900 rpm. Premium features of the engine include dual overhead camshafts with variable valve timing, chaindriven cams, 1.4L 4-cylinder turbo roller-finger camshaft followers, piston-cooling oil jets and integrated oil cooler, and a variable-flow oil pump. The 1.4L engine s turbocharger is integrated within the exhaust manifold, for reduced weight and greater packaging flexibility. Models with a manual transmission also feature Hill Start Assist (HSA). When stopped on a hill, HSA prevents the vehicle from rolling before driving off, whether facing uphill or downhill, by holding the brake pressure (for up to two seconds) during the transition between when the driver releases the brake pedal and starts to accelerate. TIP: Hill Start Assist will not operate if StabiliTrak is disabled. The electrical system of the Sonic features the Global A electrical architecture, which requires the use of the Global Diagnostic System (GDS) software and the Multiple Diagnostic Interface (MDI) tool. Suspension The ride and handling of the Sonic was a major focus for engineers. The body structure is designed to be one of the stiffest in the segment, enabling the ride and handling to be tuned more precisely. All models feature a MacPherson strut front suspension with coil springs and a stabilizer bar, and a semi-independent, torsion beam axle-mount compound link-type rear suspension with a robust, tubular V-shape beam and gas-charged shocks. The rear axle is a straight axle without contour for packaging restraints and reduced noise, vibration and harshness. Electronic power steering and StabiliTrak electronic stability control with rollover sensing are standard on all models. The columnmounted electronic power steering features a wear compensator that continually adjusts the system interaction with the steering gear to ensure precise steering action over the life of the system. On various models, 15-, 16- and17-inch alloy wheels are available. Interior Features The Sonic offers a number of convenience features, including a variety of ways for owners to stay connected. Available features include OnStar, XM satellite radio, USB and Bluetooth functionality and the MyChevrolet mobile application with OnStar RemoteLink vehicle connectivity. For operating portable audio devices, a 3.5mm auxiliary input jack is located on the radio. An optional second auxiliary input jack and USB port are located in the instrument panel upper storage compartment. Some supported devices can be recharged when connected to the USB port. The instrument cluster continues the sporty styling theme with a motorcycle-inspired large, round analog tachometer set within an asymmetrical LCD readout, with a large digital speedometer display. The Driver Information Center features a Trip/Fuel menu and a Vehicle Information menu, which include items such as tire learn, remaining oil life and fuel economy. Pressing the Menu button on the turn signal lever switches between the two menus displayed on the instrument cluster. Rotating the arrow switch on the turn signal lever displays the various items of each menu. To reset the trip odometer, press the Menu button to display the Trip/Fuel menu and then rotate the arrow switch to highlight the trip odometer. With the odometer flashing, press the reset stem on the tachometer on the instrument cluster to reset it. Comprehensive safety features on the Sonic include 10 standard air bags, antilock brakes, electronic brake force distribution and brake assist, and OnStar with Automatic Crash Response. Service Training Several service training courses on the Sonic will be available, including: W Chevrolet Sonic New Model Features (U.S.) W Chevrolet Sonic New Model Features (Canada) Go to (or in Canada) for more information. Thanks to Hassan Abdallah 2 August 2011

3 SRX Reprogramming Updates Recent service updates on the SRX require reprogramming the Sensing and Diagnostic Module (SDM) and Engine Control Module (ECM). The SRX has unique Global A programming characteristics. Review the following programming tips and incorporate them in your programming best practices. To ensure a successful programming event, it s important that no steps are missed. Before Programming TIP: Ensure the vehicle to be programmed meets the bulletin criteria before beginning programming. Proper battery voltage Just because the vehicle was just driven in, doesn't always mean it has adequate battery voltage. To maintain proper battery voltage during programming, connect the Midtronics PSC charger or GR8 battery tester/charger to the vehicle. Insufficient battery voltage can cause programming to fail or the Multiple Diagnostic Interface (MDI) to unexpectedly lose its connection. Connectivity to TIS2Web, MDI and the vehicle The Techline PC must have a reliable connection to TIS2Web and the MDI must be properly connected. A USB connection may be the best choice when programming multiple control modules. Proper ignition switch position Be sure the ignition is Put the ignition in the ON mode with the engine off. The green LED indicator on the Start/Stop button will illuminate. in the ON (or RUN) mode with the engine off. The SRX is equipped with a push button start ignition. Push button ignitions can be difficult to put in the ignition ON, engine OFF mode. TIP: Look for a full gauge sweep on the IPC, and lights ON warning. To put the ignition in this mode, press and hold the Start/Stop button (without pressing the brake pedal) for a minimum of 10 seconds. The instrument cluster will turn on, with a full gauge sweep and the Cadillac crest displayed on the Driver Information Center. The green LED indicator on the Start/Stop button will illuminate. Once the ignition is ON, begin the module set-up procedure. After Programming Programming and Setup are two different procedures After reprogramming the SDM, an SDM Setup procedure must be performed. Also, an ignition Power Mode cycle must be performed during the SDM procedure. The ignition must be in the ON position; otherwise, the setup procedure will fail. If programming stops or fails In the event that programming is interrupted or fails, DO NOT replace the control module. There are steps that can be taken in order to recover the control module. If unsuccessful, contact the Techline Customer Support Center (TCSC) at (French: ). Before calling the TCSC, be sure to have: Dealer information (BAC Code) VIN of the vehicle being reprogrammed Reason for the reprogramming procedure Any displayed error messages Close proximity to the Techline PC and vehicle Thanks to Mike Waszczenko Compressed Natural Gas Fuel Systems Training Compressed Natural Gas (CNG) Training course W is now available on (U.S. only). The Web-based Training (WBT) course covers the operation and service of the CNG fuel system available in the 2011 Express and Savana cargo vans. The course reviews the information necessary for service technicians to identify and describe the components, system operation and diagnostics of the CNG fuel system. In addition, proper refueling procedures are presented along with information related to CNG tank inspections, federal laws and government regulations for all GM CNG vehicles. Updated Procedure The fuel tank venting procedure in the course content instructs the technician to use the Tech 2 to energize the fuel pump relay. The Service Information has been updated since the course was released to the following more efficient procedure: Use a fused jumper wire to jumper the fuel pump relay terminals 30 to 87 to begin the venting process. The CNG fuel tank is completely vented when venting gas flow is no longer audible from the vent stack. CNG Training course W If ambient temperature is lower than 45 F (7 C), warm the fuel tank and vent assembly by placing in a warm environment or spraying with warm water. Thanks to Chris Graham August

4 Two-Mode Hybrid Electronic Brake Control Module DTCs DTC C0561 may be set in the Electronic Brake Control Module (EBCM) on some Escalade Hybrid, Silverado Hybrid and Sierra Hybrid models; and some Tahoe and Yukon Hybrid models. These models feature the Two-Mode Hybrid System (RPO HP2). A Service Stability message will be displayed on the Driver Information Center as a result of DTC C0561. It may be difficult to clear DTC C0561 sym4b or C0561 sym71 from the EBCM. TIP: Do not replace the EBCM. Address any DTCs in all modules before trying to clear DTC C0561. Brake Bleed Procedures If either of the DTCs are setting after the brake hydraulic system was opened or if the DTCs set on a vehicle that still has low mileage, run the Antilock Brake System Automated Bleed procedure outlined in Service Information (SI) Document ID: If the procedure was run once already and DTC C0561 sym4b resets, run the Brake Hydraulic and Assist System Diagnosis (Two-Mode Hybrid) procedure in SI Document ID: J A Brake Bleeder Adapter prior to replacing any parts. The procedure may need to be run more than one time if the procedure is not followed completely or if the incorrect brake bleed equipment is used. The recommended special tools are: J A Brake Bleeder Adapter, or equivalent J Diaphragm Pressure Bleeder or J A Brake Pressure Bleeder, or equivalent. EBCM Relearn Procedure If there are no longer any codes in any modules, perform the EBCM Relearn procedure outlined in #PIT4563F. TIP: The Brake Pressure Modulator Valve (BPMV)/EBCM assembly must be at least 32 F (0 C) or warmer before performing the set-up procedures. Use a contact thermometer or an infrared temperature gun to measure the temperature. Thanks to Brian Ciaverella J Diaphragm Pressure Bleeder Brake Pad Wear and Fit On some Cobalt, 2005 Pursuit (Canada only), and G5 models, the inner rear brake pads may have uneven wear and/or the inner pad may not fit properly. These conditions may occur after the vehicle has had the rear pads replaced. The excessive wear on the rear inner brake pads and the appearance of improper fit may be due to the pads being incorrectly installed. Outer rear brake pad with the locating pins placed top-to-bottom. The inner and outer pads can be distinguished by an anti-rattle spring and the locating pins. The inner pad has an anti-rattle spring attached to it and the locating pins are placed side-to-side. The outer pad does not have an anti-rattle spring and the locating pins are placed top-tobottom. Check that the correct pad is used before installation. Thanks to Ernest Haller Inner rear brake pad with the anti-rattle spring and the locating pins placed side-to-side. Coolant Leak from HVAC System If there is an engine coolant odor in the interior, an engine coolant loss, or if the inside of the windshield is fogging on some Camaro models, there may be coolant leaking from the HVAC system. Follow the published Loss of Coolant inspections as outlined in the Service Information to determine the origin of the leak. TIP: Due to the complexity of heater core replacement, it s important to verify that engine coolant is leaking from the heater core before beginning any heater core repairs. Thanks to Jeremy Richardson 4 August 2011

5 Intermittent No Start Condition and Illuminated MIL On the 2011 Cruze, some of the following conditions may be present: An intermittent No Crank/No Start condition Intermittent ABS, Traction Control System (TCS)/StabiliTrak Malfunction Indicator Lamp (MIL) illumination Intermittent Driver Information Center service messages being displayed: Service StabiliTrak or Service Traction Control. Any of the following DTCs also may be set: C0186, C0196, C0035, C0040, C0045, C0050, C0710, C0800, U0073, U0121, U0125, U0126, U0140, U0155, U0173, and U0174. If these conditions are present, check for excessive wire tension at the Electronic Brake Control Module (EBCM) connector. Remove the EBCM harness connector body wire dress cover and inspect for sufficient wire harness length into each respective terminal cavity. This inspection must be performed by re-installing the connector on the EBCM. Inspect each respective circuit wire length. It should be relaxed entering the terminal cavity and not under any tension. In addition, for a No Crank/No Start condition, inspect the EBCM connector for possible poor or low drag terminal tension on the High-speed Bus respective circuits (Terminals 9, 10, 11, and 12). Replace all terminals that are found to have low drag or tension. For intermittent ABS, Traction Control System and StabiliTrak lamp illumination, inspect the EBCM connector for possible poor or low drag terminal tension on all EBCM circuits (including Power & Grounds). Replace all terminals that are found to have low drag or tension. Reference the Service Information Component Connector End Views K17 Electronic Brake Control Module for test probe and replacement terminal part numbers. If the EBCM wiring harness passes all inspections, perform the same inspections on the remaining High-speed Bus communication circuits 2500 & 2501, including the Engine Control Module (ECM), Body Control Module (BCM), Fuel Pump Control Module (FPCM), Power Steering Control Module (PSCM), and Transmission Control Module (TCM). Thanks to Christopher Hightower K17 Electronic Brake Control Module connector Air Trapped in Brake System On the Impala and Monte Carlo, it may be difficult to remove all the air from the brake system after a hydraulic component disconnect or replacement. The brake lines between the master cylinder and the ABS module are routed higher than the master cylinder reservoir. If air gets into these lines, due to a component disconnect or replacement, it will rise to the high point in the lines. Extra steps must be taken to purge all of the air from the lines. To purge air from the brake lines: 1. Carefully loosen the fittings on the lines between the master cylinder and the Brake Pressure Modulator Valve (BPMV) just enough to be able to rotate the lines temporarily below the fluid level of the reservoir, then tighten the fittings. There is a flexible portion in each of these lines, which makes repositioning possible. TIP: Loosen the fittings just enough to allow the lines to move, not enough to allow air to enter. 2. Perform the bleed procedure. Bleed the left front/right rear diagonal pair of wheel cylinders, followed by the right front/left rear diagonal pair of wheel cylinders. This increases fluid flow to assist in purging air from the lines. TIP: Use a GM-recommended pressure bleeder to bleed the brakes. 3. When the bleed procedure is complete, carefully loosen the fittings on the lines repositioned earlier. Move them back to their original positions and retighten. Thanks to Dave Eplin Insufficient Windshield Washer Spray On some TrailBlazer, Envoy; Rainier; Bravada; and Saab 9-7X models, the windshield washers may be inoperative or have insufficient fluid spray. This may be caused by plugged washer nozzles and a contaminated washer reservoir. If debris is left in the reservoir, it may cause the system to become plugged. The source of the debris is typically from a loose or unfastened cap after a fluid refill. If the system is plugged, first remove the washer reservoir, remove all fluid from the reservoir and wash it out. The nozzles also must be replaced. There is a filter in the nozzles, so blowing them out will not clear them properly. Before installing new nozzles, fill the system and flush the system by activating the washer to clean out the pump and lines. Thanks to James Miller August

6 Instant Update of the Ambient Temperature Sensor determine if the display will read an accurate temperature. To perform an instant update of the Ambient Temperature Sensor, simultaneously press and hold the Recirculation button and A/C button on the HVAC control head. It is also possible to perform the instant update by using a scan tool in the special function mode and selecting instant OST update. Within a few seconds, the Driver Information Center should display the current temperature. If the instant update creates an accurate reading, do not replace the Ambient Temperature Sensor. Explain to owners how the system is designed to filter the ambient temperature sensor reading to prevent erratic readings in temperature. The ambient temperature display may be slow to update the outside temperature at times or the A/C compressor may not operate due to low ambient temperature on some Enclave; Traverse; OUTLOOK; Acadia, Escalade, Escalade ESV, Escalade EXT, Avalanche, Silverado, Suburban, Tahoe, Sierra, Yukon, Yukon Denali, Yukon XL, and Yukon Denali XL models. The outside air temperature display utilizes a very specific filtering routine of the Ambient Temperature Sensor signal so the display will update gradually without making large jumps in the reading. This is designed to eliminate the possibility of erratic readings under certain driving conditions. The temperature display is always allowed to update quickly when the ambient temperature is getting colder while driving, but the display takes much longer to update when the temperature is getting warmer. This prevents false updates to the temperature display while driving in slow or stop-and-go traffic in hot weather. The temperature display will always read the actual ambient temperature when the vehicle is started if the temperature has dropped since the last key cycle. It will not immediately update to the actual ambient temperature if it has gotten warmer since the last key cycle unless the ignition has been off for at least 2.5 hours. Instant Update If an owner has a concern with the function or accuracy of the ambient air temperature display, perform the instant update to A/C Compressor Operation Additionally, when diagnosing an HVAC system concern, keep in mind that the A/C compressor will not engage when the ambient temperature is too low as determined by the Ambient Temperature Sensor. The A/C compressor is disabled in temperatures below 36 F (2 C). Typically, this will occur when the vehicle is parked outside in temperatures below 36 F (2 C) and then brought into the service center. Since the ambient temperature does not update instantly, it will be necessary to perform an instant update of the Ambient Temperature Sensor in order to proceed with any diagnostics. Thanks to James Miller Inoperative Fuel Gauge An inoperative fuel gauge that is stuck on E (Empty) with a full tank of fuel on some Cobalt, 2005 Pursuit (Canada only), and G5 models may be the result of overfilling the fuel tank. With this condition, DTC P0461may set in the ECM. After clearing the code, the fuel gauge will begin to read correctly. Do not replace any parts for this condition without verifying how the fuel tank is being filled and how often the vehicle is refueled. Review this condition with owners. It can be induced in the following ways: If the owner overfills the fuel tank to the point where the ECM/ PCM cannot indicate a 1.6% drop in fuel within 120 miles (193 km) of driving, the DTC will set and the fuel gauge will default to E. If the owner fills the vehicle too frequently (before the fuel gauge reading starts to drop), the ECM/PCM cannot indicate a 1.6% drop in fuel within 120 miles (193 km) of driving. The DTC will set and the gauge will default to E. To prevent the fuel gauge from defaulting to E, inform the owner to avoid overfilling the fuel tank by stopping the pump after it clicks off. In addition, do not fill the vehicle until the fuel gauge drops below Full or the vehicle is driven more than 120 miles (193 km). Thanks to Ernest Haller 6 August 2011

7 GM TechLink is a monthly magazine for all GM retail technicians and service consultants providing timely information to help increase know ledge about GM products and improve the performance of the service department. Publisher: Thomas J. Arnold GM Customer Care and Aftersales /Thomas.Arnold@GM.com Editor: Lisa G. Scott GM Customer Care and Aftersales /Lisa.G.Scott@GM.com Technical Editor: Mark Spencer /mspencer@gpworldwide.com Production Manager: Marie Meredith Desktop Publishing: 5by5 Design LLC /dkelly@5by5dzign.com FAX number: Write to: * TechLink PO Box 500 Troy, MI 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 2011 General Motors All rights reserved. Sunroof Sunshade Relearn When attempting to close the sunroof sunshade on the LaCrosse, if it closes approximately half way and then stops, it may need to be reprogrammed. Using GDS 2, select Module Diagnostics > Body Control Module > Data Display. From the Select Data List Menu at the top of the page, select Sunroof Data from the drop down menu. Review Sunroof Position from the data list, which will indicate the actual position of the sunroof. The inside rear view mirror on the Malibu has an automatic day-night feature that can be turned on or off. To enable or disable the automatic daynight feature of the inside rear view mirror, with the ignition in the On position, depress and hold the on/off button on the mirror for six seconds. A green indicator will illuminate on the mirror when the automatic day-night feature is enabled. Service Know-How D Emerging Issues If the Sunroof Position from the data list does not indicate the correct position, perform the Sunroof Motor/Actuator Initialization/Teach Process (Existing Motor) following Service Information Document ID: Once the relearn has been completed, the sunroof sunshade should close properly. Thanks to Christopher Crumb Inside Rear View Mirror Automatic Day-Night Feature Fog Lamp Operation To disable the automatic day-night feature, depress and hold the on/off switch for six seconds again. Be sure to inform owners of the length of the button press in order to enable or disable the automatic day-night feature. Information in the Owner Manual may be incomplete. Thanks to Chris Hightower Camaro models equipped with HID Headlamps (RPO T4F) have Daytime Running Lamps (DRLs) in place of the fog lamps. This information is called out in the Owner Manual. If an owner comments that the fog lamps are inoperative, before making any repairs, check that the vehicle is equipped with fog lamps, not the DRLs. Owners who would like to have fog lamps added to a vehicle that was not originally built with fog lamps should be informed that GM does not offer an approved fog lamp kit for these vehicles. Thanks to Jeremy Richardson August 11, 2011 To view Emerging Issues seminars: Log in to select Service Know-How/ TECHAssist from the menu, select Emerging Issues, and then Searchable Streaming Video to choose the current Emerging Issues seminar or past programs. August

8 Car Issues Fix It Right the First Time Model Year(s) Vehicle Line(s)/Condition Do This Don t Do This Reference Information/Bulletin 2011 CTS, CTS Coupe, CTS Sport Wagon Differential gear whine or pinion gear whine from rear axle Order the isolator kit P/N Order WPC 591 PI0350C Malibu Power steering or DIC Reduced Power message, DTC C0475 or P2138 set Check that water leak is not the cause for DTC C0475 and/or P2138 Overlook water leaks as a cause PI0116A 2011 Acadia, Avalanche, Canyon, Colorado, Corvette, Escalade, models, Express, Impala, Malibu, Savana, Tahoe, Traverse, Yukon models DTCs P0442, P0446, P0455 or P0449 set; Corrosion at EVAP CVS Valve electrical terminals, Fuel tank hard to fill If corrosion is present in connector, clean or replace connector and apply dielectric grease Repair without correcting corrosion PI Cruze Intermittent trunk inoperative, DTC B3618 Replace rear license plate lamp wire harness Adjust or replace rear striker or latch assembly PI Impala ABS and Traction Control light On Check wiring problem areas Replace EBCM PI All Vehicles Interior cleaning product availability Vacuum loose dirt as first step in cleaning Replace dirty parts that could be cleaned G Lucerne Noise when shifting from Park to Reverse or Drive, Noise in power steering system Inspect/replace the front engine mount if separated. Inspect power steering fluid reservoir for signs of leaking Replace the power steering reservoir without looking at the front engine mount for separation PI Caprice PPV USB Diagnostic Cable EL required when reprogramming radio Purchase USB Cable and perform radio programming Replace radio for software updates PI Corvette Thin finish in lug nut recesses on optional gloss black wheels Brush paint the lug nut opening Replace the wheel PI Malibu Water leak into footwell or within IP and/or lower dash panel insulators Review bulletin when diagnosing a 2010 or 2011 water leak Overlook water leaks in the roof ditch area PI0096A 2011 Camaro Wind noise from front door glass at highway speed Reposition the convertible top side tension cable Replace the front rail weatherstrip PI Camaro, Caprice PPV, Cruze, Equinox, G8, LaCrosse, Regal, Terrain, Volt Key cutting procedure for obtaining replacement key Information update only Information update only G 8 August 2011

9 Truck Issues Fix It Right the First Time Model Year(s) Vehicle Line(s)/Condition Do This Don t Do This Reference Information/Bulletin VUE Information on air conditioning compressor replacement from 1st design to 2nd design When installing a 2nd design A/C compressor, replace/modify all components called out in the bulletin Replace the compressor without additional parts required Express, Savana Release of steering linkage inner tie rod kit for service Replace the inner tie rods Replace the complete rack PI Acadia, Enclave, Outlook, Traverse Lower control arm bushing squeak when warm Replace the bushing Replace the lower control arm PI0251A Avalanche, Sierra, Silverado, Suburban, Tahoe, Yukon; Yukon Denali, Yukon XL, Yukon XL Denali Reduced window clearing, nonresponsive HVAC Control Reflash HVAC module Replace module or actuators A Sierra, Silverado Noise from underbody over bumps Replace with new design cable Apply grease A Canyon, Colorado Excessive blower motor noise on low speed Evaluate the source of the noise. If the HVAC blower motor has excessive noise, install the recommended insulator cover Replace the HVAC blower motor D 2011 Sierra, Silverado Instrument panel cluster warning lamps/mil illuminated, DEF message displayed, various DTCs set, transmission may not shift or defaults to second gear Repair wiring or connector Replace components PI0339A Equinox, Torrent, VUE Information on individual steering column part component availability Replace the steering column assembly (minus motor and ECU) Replace the steering column assembly kit PI0440A Escalade, Tahoe, Yukon Transmission shudder or bucking feel Replace the pressure regulator valve inner spring Replace transmission C Customer Care and Aftersales August