Service Bulletin Bulletin No.: 19-NA-091 Date: June, 2019

1 Copyright 2019 General Motors LLC. All Rights BulletinBulletin No.: 19-NA-091 Date: June, 2019 INFORMATIONS ubject: 2020 Chevrolet Silverado and GMC Sierra 2500HD-3500HD New Model FeaturesBrand:Model:Model Year:VIN:Engine:Transmission:From:To:Fro m:To:ChevroletGMCS ilverado2500HD-3500 HDSierra2500HD-3500HD2020 , V8, SIDI,VVT, Cast Iron,Gasoline RPO L8 TDuramax , DI,TurbochargedDiesel, GEN 5,VAR. 1 RPO L5P6-SpeedAutomatic6L90, HMD, RPO MYDA llison 10-SpeedAutomatic10L1000, GRX,GEN 1, VAR 1 RPO MGMORA llison 10-SpeedAutomatic10L1000, GRX,GEN 2, VAR 2with PTO RPO MGUI nvolved Countries and Regions North America, South America, Israel and Middle EastOverviewBulletin PurposeThis purpose of this Bulletin is to introduce thecompletely new 2020 Chevrolet Silverado and GMCS ierra 2500HD-3500HD pickup trucks.

2 This Bulletin willhelp the Service Department Personnel becomefamiliar with the all-new V8 RPO L8T gasolineengine equipped with the 6-speed 6L90 automatictransmission, and the Duramax V8 RPO L5 Pdiesel engine equipped with the all-new Allison Branded - General Motors manufactured 10-speedautomatic transmission with an available integratedPTO option, the brake system , SIR system , and othergeneral information for these in -ton 2500, 1-ton 3500 single rear wheel,and 1-ton 3500 dual rear wheel configurations with2WD or 4WD. These trucks have at least 10 inches( cm) of ground clearance, with an improvedapproach angle, and a repositioned diesel exhaust fluid(DEF) tank on the diesel models enabling additionalground trucks are very connected, with options thatinclude OnStar , Commercial Link, a built-in OnStar 4G LTE Wi-Fi Hotspot (requires a paid data plan),as well as Inductive Charging for capable PortableWireless Devices and Bluetooth capability.

3 They alsosupport the Apple CarPlay software feature andAndroid Auto highlights include: A modular front on the trucks enables easiermounting of a snowplow. Advanced cooling system for vehicles equippedwith the Duramax RPO L5P. Coolingcapacity is increased by use of a larger radiator,an immense cooling fan, and by improving the airinduction system . A dual-path intake systemdraws dense, cool air through both the hoodscoop and the front grille in order to optimizeperformance. Available 120 V alternating current power outletlocated at the rear of the box. It can be used toplug in electrical equipment that uses a maximumof 150 2 June, 2019 Bulletin No.

4 : 19-NA-091 Available Autotrac Active 2-speed transfer caseon 4WD models that electronically controls 4 Auto mode. Available dual alternators on both engine optionsmake it easy to power any accessories needed forcommercial applications. Available Power Up/Down Tailgate (Silverado)that raises or lowers using the key fob, interiorbutton or the touchpad on the tailgate. Silverado provides BedSteps located in front ofthe rear wheel openings allowing easier accessfrom the side of the vehicle. The Sierra isequipped with the same equipment, however theyare known as Bed side steps. Both complementthe integrated CornerSteps in the rear bumper ofthe vehicles that have increased in size also toimprove access to the cargo GMC s innovative and exclusive MultiPro Tailgateis standard on SLT, AT4, and Denali models andcan be configured and used in six different ways,including as a step and a load stop for long Other features include an easy access enginecoolant block heater outlet, easy to fill dieselexhaust fluid (DEF) tank with its opening inside ofthe fuel door.

5 Sierra has 12 corner tie-downs. Silverado has 12 fixed tie-down rings, with thecorner rings rated at 500 pounds (227 kg) and theability to add up to nine accessory tie downs. Vehicles have a Trailering Info Label placed on thedriver s door jamb which identifies the truck sspecific trailering information, including curbweight, GVWR, GCWR, maximum payload,maximum tongue weight and rear GAWR. Vehicles equipped with the Duramax V-8 Turbocharged engine and the 10-speed automatictransmission provide a 52 percent increase inmaximum towing capability to 35,500 pounds(16,103 kg) on properly equipped Description and OperationThe electronic brake control module (EBCM) and thebrake pressure modulator are serviced separately.

6 Thebrake pressure modulator uses a four circuitconfiguration to control hydraulic pressure to eachwheel on options, the following vehicleperformance enhancement systems may be provided: ABS Traction Control Stability Control Dynamic Rear Proportioning Hill Descent Control system Hill Hold Start Assist Hydraulic brake Assist Intelligent brake AssistBulletin No.: 19-NA-091 June, 2019 Page 3 Trailer brake Control system Trailer Sway ControlABSWhen wheel slip is detected during a brake application,an ABS event occurs. During ABS braking, hydraulicpressure in the individual wheel circuits is controlled toprevent any wheel from slipping as needed.

7 A separatehydraulic line and specific solenoid valves are providedfor each wheel. The ABS can decrease, hold, orincrease hydraulic pressure to each wheel. The ABSdoes not increase hydraulic pressure above the amountwhich is transmitted by the master cylinder duringbraking. During an ABS braking event, a series of rapidpulsations may be felt in the brake Activation SequenceThe typical ABS activation sequence is as follows: Pressure Hold:The EBCM closes the isolationvalve and keeps the dump valve closed in order toisolate the slipping wheel when wheel slip holds the pressure steady on the brake sothat the hydraulic pressure does not increase ordecrease.

8 Pressure Decrease:If a pressure hold does notcorrect the wheel slip condition, a pressuredecrease occurs. The EBCM decreases thepressure to individual wheels as needed duringdeceleration when wheel slip occurs. The isolationvalve is closed and the dump valve is opened. Theexcess fluid is stored in the accumulator until thepump can return the fluid to the master cylinder orfluid reservoir. Pressure Increase:After the wheel slip iscorrected, a pressure increase occurs. The EBCM increases the pressure to individual wheels asneeded during deceleration in order to reduce thespeed of the wheel. The isolation valve is openedand the dump valve is closed.

9 The increasedpressure is delivered from the master ControlWhen drive wheel slip is noted, the EBCM will enterTraction Control (TC) mode. First, the EBCM requeststhe engine control module (ECM) to reduce the amountof torque to the drive wheels via a serial data ECM reduces torque to the drive wheels andreports the amount of delivered torque. If the enginetorque reduction does not reduce drive wheel slip, theEBCM will actively apply the brakes on the slippingdrive wheel. During TC braking, hydraulic pressure ineach drive wheel circuit is controlled to prevent thedrive wheels from slipping. The EBCM commands thepump motor and appropriate solenoid valves ON andOFF to apply brake pressure to the slipping wheel.

10 TCcan be manually disabled or enabled by pressing theTC ControlStability Control provides added stability duringaggressive maneuvers. Yaw rate is the rate of rotationabout the vehicle's vertical axis. The stability control isactivated when the EBCM determines that the desiredyaw rate does not match the actual yaw rate asmeasured by the yaw rate sensor. The desired yaw rateis calculated by the EBCM using the following inputs:steering wheel position, vehicle speed and lateralacceleration. The difference between the desired yawrate and the actual yaw rate is the yaw rate error, whichis a measurement of oversteer or understeer.