N222391080 Defective Suspension Nuts – 2021-2022 Chevrolet 4500HD/5500HD/6500HD

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GLOBAL SAFETY FIELD INVESTIGATIONS DCS6351 URGENT – DISTRIBUTE IMMEDIATELY Date: November 23, 2022 Subject: Stop Delivery Order for Upcoming Safety Recall N222391080 Defective Suspension Nuts Models: 2021 – 2022 Chevrolet Silverado 4500HD/5500HD/6500HD To: All General Motors Medium Duty Dealers STOP DELIVERY ORDER Effective immediately, stop the delivery of certain 2021 – 2022 model year Chevrolet 4500HD/5500HD/6500HD vehicles in new or used vehicle inventory. General Motors has notified the National Highway Traffic Safety Administration (NHTSA) about an upcoming safety recall that involves these vehicles. The GM recall number is N222391080. It is a violation of federal law for a dealer to deliver a new motor vehicle or any new or used item of motor vehicle equipment (including a tire) covered by this notification until the defect is remedied. Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. Parts are not currently available, but when parts are available, dealers are to replace suspect lock nuts. Until further instructions are received, involved vehicles that are in dealers’ possession (new or used vehicle inventory, GM Certified Used, courtesy transportation vehicles, dealer shuttle vehicles, etc.) must be held and not delivered to customers, dealertraded, released to auction, used for demonstration purposes or any other dealer use. All GM Certified Used vehicles currently in the dealers’ inventory within the Certified Pre-Owned Inventory System (CPOIS) will be de-certified. The Investigate Vehicle History (IVH) screen in the Global Warranty Management (GWM) system has been updated for this upcoming recall. This action has been taken to assist dealers with determining which vehicles are involved so they can properly respond to customer inquiries. A list of involved vehicles that have been identified as being in dealer new vehicle inventory is attached to this message. It is sorted by dealer Business Associate Code (BAC) for easy reference. Your dealership’s BAC will not be listed if none of the involved vehicles are currently in your new vehicle inventory. To identify involved vehicles in dealer used inventory, run an Open VIN Report or Field Action Initiation Report using Field Action Reports-GFAM within the Maxis Dealer Application in GlobalConnect. Question and Answer Document (Q&A) Attached to this message you will find a document that addresses the ten most likely questions customers may have regarding this Safety Recall. Please use this information as an aid to confidently answer customer concerns. Until the recall bulletin is released, the Investigate Vehicle History (IVH) screen in the Global Warranty Management (GWM) system will display “11/23/2022” under Release Date and “Incomplete – Remedy Not Available” under Status. This means the required repair is not yet available and dealers should not attempt to perform any repairs. We are working with the supplier to obtain the required parts as quickly as possible. When a sufficient quantity of parts are available, the recall bulletin will be released and dealers can begin repairing vehicles. END OF MESSAGE GLOBAL SAFETY FIELD INVESTIGATIONS

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OMB Control No.: 2127-0004 Part 573 Safety Recall Report 22V-874 The information contained in this report was submitted pursuant to 49 CFR §573 Manufacturer Name : General Motors, LLC Submission Date : NOV 23, 2022 NHTSA Recall No. : 22V-874 Manufacturer Recall No. : N222391080 Manufacturer Information : Manufacturer Name : General Motors, LLC Address : 29427 Louis Chevrolet Road MAIL CODE 480-210-2V WARREN MI 48093 Company phone : 586-596-1733 Population : Number of potentially involved : 5,861 Estimated percentage with defect : 100 % Vehicle Information : Vehicle 1 : 2021-2022 Chevrolet 4500HD/5500HD/6500HD Vehicle Type : Body Style : Power Train : NR Descriptive Information : Manufacturing records were used to identify vehicles built within the affected build window. Vehicles built outside of the affected build window are not affected. Production Dates : JAN 18, 2022 – AUG 12, 2022 VIN Range 1 : Begin : NR End : NR Not sequential Description of Defect : Description of the Defect : General Motors has decided that a defect which relates to motor vehicle safety may exist in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. FMVSS 1 : NR FMVSS 2 : NR Description of the Safety Risk : Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. Description of the Cause : NR Identification of Any Warning that can Occur : Drivers may notice a degradation in vehicle handling. Part 573 Safety Recall Report 22V-874 Page 2 The information contained in this report was submitted pursuant to 49 CFR §573 Involved Components : Component Name 1 : NUT Component Description : 3/4″ – 16 Hex Flange Lock Nut Component Part Number : 416743C2 Supplier Identification : Component Manufacturer Name : Navistar, Inc Address : 6125 Urbana Road Springfield Ohio 45502 Country : United States Chronology : On November 18, 2022, Navistar informed GM that it was investigating a quality issue in certain hex flange lock nuts used in 2021-2022 model year Chevrolet Silverado Medium Duty vehicles, and that it had decided to conduct a safety recall to address this condition in Navistar-badged vehicles in the field. After consulting with Navistar, GM’s Safety Field Action Decision Authority (SFADA) decided to conduct a safety recall on November 22, 2022. Description of Remedy : Description of Remedy Program : Dealers will replace suspect lock nuts. Pursuant to 49 C.F.R. § 573.13(d)(1), all covered vehicles are under warranty, so reimbursement is not offered. How Remedy Component Differs from Recalled Component : Replacement lock nuts are made to Navistar’s specified form and surface hardness. Identify How/When Recall Condition was Corrected in Production : NR Recall Schedule : Description of Recall Schedule : Dealers will be notified on November 23, 2022. GM estimates owner notification will begin on January 9, 2023. Planned Dealer Notification Date : NOV 23, 2022 – NOV 23, 2022 Part 573 Safety Recall Report 22V-874 Page 3 The information contained in this report was submitted pursuant to 49 CFR §573 Planned Owner Notification Date : JAN 09, 2023 – JAN 09, 2023 * NR – Not Reported

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OMB Control No.: 2127-0004 Part 573 Safety Recall Report 22V-874 The information contained in this report was submitted pursuant to 49 CFR §573 Manufacturer Name : General Motors, LLC Submission Date : DEC 07, 2022 NHTSA Recall No. : 22V-874 Manufacturer Recall No. : N222391080 Manufacturer Information : Manufacturer Name : General Motors, LLC Address : 29427 Louis Chevrolet Road MAIL CODE 480-210-2V WARREN MI 48093 Company phone : 586-596-1733 Population : Number of potentially involved : 5,861 Estimated percentage with defect : 100 % Vehicle Information : Vehicle 1 : 2021-2022 Chevrolet 4500HD/5500HD/6500HD Vehicle Type : Body Style : Power Train : NR Descriptive Information : Manufacturing records were used to identify vehicles built within the affected build window. Vehicles built outside of the affected build window are not affected. Production Dates : JAN 18, 2022 – AUG 12, 2022 VIN Range 1 : Begin : NR End : NR Not sequential Description of Defect : Description of the Defect : General Motors has decided that a defect which relates to motor vehicle safety may exist in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. FMVSS 1 : NR FMVSS 2 : NR Description of the Safety Risk : Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. Description of the Cause : NR Identification of Any Warning that can Occur : Drivers may notice a degradation in vehicle handling. Part 573 Safety Recall Report 22V-874 Page 2 The information contained in this report was submitted pursuant to 49 CFR §573 Involved Components : Component Name 1 : NUT Component Description : 3/4″ – 16 Hex Flange Lock Nut Component Part Number : 416743C2 Supplier Identification : Component Manufacturer Name : Navistar, Inc Address : 6125 Urbana Road Springfield Ohio 45502 Country : United States Chronology : On November 18, 2022, Navistar informed GM that it was investigating a quality issue in certain hex flange lock nuts used in 2021-2022 model year Chevrolet Silverado Medium Duty vehicles, and that it had decided to conduct a safety recall to address this condition in Navistar-badged vehicles in the field. After consulting with Navistar, GM’s Safety Field Action Decision Authority (SFADA) decided to conduct a safety recall on November 22, 2022. Description of Remedy : Description of Remedy Program : Dealers will replace suspect lock nuts. Pursuant to 49 C.F.R. § 573.13(d)(1), all covered vehicles are under warranty, so reimbursement is not offered. How Remedy Component Differs from Recalled Component : Replacement lock nuts are made to Navistar’s specified form and surface hardness. Identify How/When Recall Condition was Corrected in Production : NR Recall Schedule : Description of Recall Schedule : Dealers will be notified on November 23, 2022. Owner interim notification is estimated to begin December 20, 2022. GM estimates owner notification will begin on January 30, 2023. Part 573 Safety Recall Report 22V-874 Page 3 The information contained in this report was submitted pursuant to 49 CFR §573 Planned Dealer Notification Date : NOV 23, 2022 – NOV 23, 2022 Planned Owner Notification Date : JAN 30, 2023 – JAN 30, 2023 * NR – Not Reported

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GM CUSTOMER CARE AND AFTERSALES DCS6361 URGENT – DISTRIBUTE IMMEDIATELY Date: December 8, 2022 Subject: N222391080 – Safety Recall Defective Suspension Nuts Application for Used Vehicle Working Capital Assistance Program (WCAP) Models: 2021 – 2022 Chevrolet Silverado 4500HD/5500HD/6500HD To: All General Motors Dealers On November 23, 2022, GM sent to all GM dealers GlobalConnect Message GCUS-3-2714 regarding safety recall N222391080. The required repair to complete this recall is not yet available. Until further instructions are received, the involved vehicles that are in dealers’ possession (new or used vehicle inventory, GM Certified Used, courtesy transportation vehicles, dealer shuttle vehicles, etc.) must be held and cannot be delivered to customers, dealer-traded, released to auction, used for demonstration purposes or put to any other use. This message is to inform dealers who have involved vehicles in their inventory that they can now apply for the used vehicle Working Capital Assistance Program (“WCAP”) for safety recall N222391080. Before proceeding with the application process described below, dealers must verify vehicle eligibility based on the program terms and guidelines that were provided in GM GlobalConnect Message GCUS-9-10968 dated March 10, 2021. Applications submitted on ineligible vehicles are subject to chargeback of any incentives paid to the dealer under the WCAP. Because compensation and tracking requires visibility into dealers’ inventory, dealers must also have agreed to a Dealer Data Share agreement with GM in order to receive any compensation under this program. To apply for the WCAP for safety recall N222391080, dealers must access the GM Global Warranty Management (GWM) system and submit a “ZSET” warranty transaction using the labor code provided below for each eligible vehicle. This zero dollar special transaction type is the dealer’s application for compensation and constitutes a representation from the dealer that the vehicle is eligible for WCAP assistance. Note: Acceptance of the warranty transaction does not ensure vehicle eligibility or guarantee the provision of any assistance as defined by program terms and guidelines. Labor Code Description Labor Time Trans Code 9800099 Working Capital Assistance for Safety Recall N222391080 N/A ZSET To be eligible for the WCAP, a vehicle must be in dealer inventory at the time the related field action bulletin is released. If a vehicle has been delivered, wholesaled or otherwise disposed of prior to release of the bulletin, the vehicle is not eligible for assistance. Additionally, recalled vehicles taken in on trade may be eligible for assistance if the dealer immediately reports the vehicle in used vehicle inventory via its Dealer Management System (DMS) and makes application through the GWM system. To ensure that GM is receiving daily inventory information, which is necessary to process payments and make eligibility determinations under the WCAP, the dealer’s vehicles must be properly identified in the dealership’s DMS. A daily feed of this information is provided to GM through the Dealer Data Share (DDS) agreement. Beginning with the 1st quarter of 2019, all WCAP payments will be facilitated through the Global Warranty Management (GWM) system. For each eligible vehicle, a qualifying dealer will submit for WCAP vehicle enrollment with a “ZSET” transaction type and for reimbursement with a “ZFAT” transaction type both through the GWM system. If approved, a WCAP credit for that vehicle will be issued through the GWM system similar to any other warranty credit. WCAP submission instructions and the required labor code will also be provided in the appropriate field action bulletin. Each WCAP transaction being credited will be clearly identified on the dealer’s daily credit memo. In order to receive payment, a dealer must have timely reported the vehicle in used vehicle inventory, retained the vehicle until the related field action bulletin is released, and properly applied for the WCAP payment. The vehicle must also be otherwise eligible under WCAP rules and guidelines. GM reserves the right to amend, modify, terminate, or cancel this program at any time in its sole discretion. END OF MESSAGE GM CUSTOMER CARE AND AFTERSALES

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IMPORTANT SAFETY RECALL December 2022 This notice applies to your vehicle, VIN: __________________________________ Dear General Motors Customer: This notice is sent to you in accordance with the National Traffic and Motor Vehicle Safety Act. General Motors has decided that a defect which relates to motor vehicle safety exists in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. As a result, GM is conducting a safety recall. We apologize for this inconvenience. However, we are concerned about your safety and continued satisfaction with our products. IMPORTANT • Your vehicle is involved in GM safety recall N222391080. Why is your vehicle being recalled? Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. What will we do? Parts to repair your vehicle are not currently available, but when parts are available, your GM dealer will replace suspect lock nuts. This service will be performed for you at no charge. We are working as quickly as possible to correct this condition. When parts are available, we will send you another letter asking you to take your vehicle to your GM dealer to have your vehicle serviced. You can also check the status of this recall at: https://my.gm.com/recalls. Do you have questions? If you have questions or concerns that your dealer is unable to resolve, please contact the appropriate Customer Assistance Center at the number listed below. Division Number Text Telephones (TTY) Chevrolet 1-800-630-2438 1-800-833-2438 Puerto Rico – English 1-800-496-9992 Puerto Rico – Español 1-800-496-9993 Virgin Islands 1-800-496-9994 For the hearing or speech impaired, please contact our Customer Assistance Center using the Telecommunication Relay Service by dialing 711 then providing the appropriate Customer Assistance Center number for your vehicle. If after contacting your dealer and the Customer Assistance Center, you are still not satisfied we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., Washington, DC 20590, or call the toll-free Vehicle Safety Hotline at 1.888.327.4236 (TTY 1.800.424.9153), or go to http://www.nhtsa.gov. The National Highway Traffic Safety Administration Campaign ID Number for this recall is 22V874. Federal regulation requires that any vehicle lessor receiving this recall notice must forward a copy of this notice to the lessee within ten days. Regina Carto Vice President Global Vehicle Safety and Systems GM Recall: N222391080

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Product Safety Recall N222391080 Defective Suspension Nuts Copyright 2023 General Motors. All Rights Reserved. Page 1 of 6 Release Date: February 2023 Revision: 01 Revision Description: This bulletin is being revised to update the Service Procedure. Please discard all previous copies of N222391080. Attention: It is a violation of Federal law for a dealer to deliver a new motor vehicle or any new or used item of motor vehicle equipment (including a tire) covered by this notification under a sale or lease until the defect or noncompliance is remedied. Vehicles involved in this recall were placed on stop delivery November 23, 2022. Once the service procedure contained in this bulletin has been performed on the vehicle, the vehicle is released from stop delivery and the vehicle can be delivered to the customer. All involved vehicles that are in dealer inventory must be held and not delivered to customers, dealer traded, or used for demonstration purposes until the repair contained in this bulletin has been performed on the vehicle. ONLY Chevrolet Medium Duty dealers can complete this recall repair. Make Model Model Year RPO Description From To Chevrolet Silverado 4500HD/5500HD/6500HD 2021 2022 Involved vehicles are marked “Open” on the Investigate Vehicle History screen in GM Global Warranty Management system. This site should always be checked to confirm vehicle involvement prior to beginning any required inspections and/or repairs. Condition General Motors has decided that a defect which relates to motor vehicle safety may exist in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. Correction Dealers will replace suspect lock nuts. Parts Quantity Part Name Part No. 6 HEX NUT 19404845 Important: Due to limited initial parts availability, dealers are encouraged not to order recall parts for use as shelf stock and parts will be removed from SPRINT. Reminder: Parts may be removed from Retail Inventory Management (RIM). Dealers should review the affected parts to confirm RIM managed status. Parts may have quantity limiters in effect. Warranty Information Labor Operation Description Labor Time Trans. Type Net Item 9106584 Replace Front Suspension Nuts 1.0 ZFAT N/A 9106585 Floor Plan Reimbursement – NEW INVENTORY ONLY N/A ZFAT * 9106586 Working Capital Assistance Program Reimbursement – USED INVENTORY ONLY N/A ZFAT ** Note: To avoid having to “H” route the floor plan / WCAP transaction for approval, it must be submitted prior to the repair transaction. Product Safety Recall N222391080 Defective Suspension Nuts Page 2 of 6 Floor Plan Reimbursement – NEW INVENTORY ONLY * USA Only – For vehicles eligible for floor plan reimbursement, the amount should be submitted in Net Item/Miscellaneous. This amount should represent the product of the vehicle’s average daily interest rate (see table below) multiplied by the actual number of days the vehicle was in dealer inventory and not available for sale. This reimbursement is limited to the number of days from the date of the stop delivery message (November 23, 2022) to the date the repair is completed, and the vehicle is ready for sale (not to exceed 68 days). Vehicle Floor Plan Reimbursement Amount USA 2021 Chevrolet Silverado 4500HD/5500HD/6500HD $13.52 2022 Chevrolet Silverado 4500HD/5500HD/6500HD $14.05 Working Capital Assistance Program (WCAP) Reimbursement – USED INVENTORY ONLY Note: USA Only – To avoid having to “H” route the WCAP transaction for approval, it must be submitted prior to the repair transaction. Important: The WCAP ZSET transaction labor code, 9800099, provided in the dealer message sent on December 8, 2022 (USA), must have been submitted prior to the submittal of the ZFAT transaction labor code or the claim will reject. ** USA Dealers Only – For vehicles eligible under the Working Capital Assistance Program, the amount should be submitted in Net Item/Miscellaneous. This amount has been calculated to a daily value for the days that the vehicle was in used dealer inventory and not available for sale. This reimbursement is limited to the number of days from the date of the stop sale/stop delivery order (November 23, 2022) to the date the inspection or repair closed the recall bulletin. (not to exceed 68 days). Vehicle Working Capital Assistance Reimbursement Amount USA 2021 Chevrolet Silverado 4500HD/5500HD/6500HD $26.25 2022 Chevrolet Silverado 4500HD/5500HD/6500HD $27.81 Service Procedure Caution: Bolt and nut installation directions may vary depending on option content. If the nut is not accessible for final torque, torque may be applied to the bolt ONLY while the vehicle is lifted in such a way as to remove the weight of the vehicle from the springs and shackles. Note: Vehicle MUST be lifted by the frame so as to remove the weight of the vehicle from the springs and shackles to achieve proper fasteners torque. 1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in SI. Product Safety Recall N222391080 Defective Suspension Nuts Page 3 of 6 4926623 Caution: Do not remove both nuts at the same time. Remove, replace, and torque each nut individually before moving to the next one. 2. One at a time, remove and replace both of the Front Leaf Spring Shackle Nuts (1) on the left side of the vehicle, torquing to 407-502 Nm (300-370 lb ft). 4926641 3. Remove and replace the Front Leaf Spring Shackle Nut (1) on the left side of the vehicle. 4. Torque the Front Leaf Spring Shackle Nut (1) to 407-502 Nm (300-370 lb ft). 5. Repeat steps 2-4 on the right side of the vehicle. 6. Lower the Vehicle. Product Safety Recall N222391080 Defective Suspension Nuts Page 4 of 6 Dealer Responsibility – For USA & Export (USA States, Territories, and Possessions) It is a violation of Federal law for a dealer to deliver a new motor vehicle or any new or used item of motor vehicle equipment (including a tire) covered by this notification under a sale or lease until the defect or noncompliance is remedied. The US National Traffic and Motor Vehicle Safety Act provides that each vehicle that is subject to a recall of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. In the recall notification letters, customers are told how to contact the US National Highway Traffic Safety Administration if the recall is not completed within a reasonable time. Dealer Responsibility – All All new, used, GM Certified Used, courtesy transportation vehicles, dealer shuttle vehicles, etc. in dealers’ possession and subject to this recall must be held and inspected/repaired per the service procedure of this bulletin before customers take possession of these vehicles. Involved vehicles must be held and not delivered to customers, dealer-traded, released to auction, used for demonstration, or any other purpose. All GM Certified Used vehicles currently in the dealers’ inventory within the Certified Pre-Owned Inventory System (CPOIS) will be de-certified and must be held and remedied per the service procedure in this bulletin. Upon submitting an accepted/paid warranty transaction in the Global Warranty Management (GWM) system, the vehicle can be re-certified for sale within the CPOIS system, or once again be used in the CTP program. Dealers are to service all vehicles subject to this recall at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward. Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. A copy of the customer letter is provided in this bulletin for your use in contacting customers. Recall follow-up cards should not be used for this purpose, since the customer may not as yet have received the notification letter. In summary, whenever a vehicle subject to this field action enters your vehicle inventory you must take the steps necessary to ensure the program correction has been made before selling the vehicle. In addition, for vehicles entering your facility for service, you are required to ensure the customer is aware of the open field action and make every reasonable effort to implement the program correction as set forth in this bulletin prior to releasing the vehicle. Dealer Reports – For USA & Export For dealers with involved vehicles, a listing has been prepared and will be available through GM GlobalConnect Maxis Field Action Reports or sent directly to export dealers. The Inventory tab of the dealer reports will contain VINs that apply to this recall. This information is intended to assist dealers with the PROMPT COMPLETION of these vehicles. The Customer In-Service tab will contain customer names and addresses from Motor Vehicle Registration Records. The use of such motor vehicle registration data for any purpose other than follow-up necessary to complete this recall may be a violation of law in several states. Customer Notification USA & Canada – General Motors will notify customers of this recall on their vehicle (see copy of customer letter included with this bulletin). GM bulletins are intended for use by professional technicians, NOT a “do-it-yourselfer”. They are written to inform these 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 tools, equipment, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your dealer for information on whether your vehicle may benefit from the information. We Support Voluntary Technician Certification Product Safety Recall N222391080 Defective Suspension Nuts Page 5 of 6 IMPORTANT SAFETY RECALL February 2023 This notice applies to your vehicle, VIN: _____________________________________ Dear General Motors Customer: This notice is sent to you in accordance with the National Traffic and Motor Vehicle Safety Act. General Motors has decided that a defect, which relates to motor vehicle safety, exists in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. As a result, GM is conducting a safety recall. We apologize for this inconvenience. However, we are concerned about your safety and continued satisfaction with our products. IMPORTANT • Your vehicle is involved in GM safety recall N222391080. • Schedule an appointment with your GM dealer. • This service will be performed for you at no charge. Why is your vehicle being recalled? Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. What will we do? Your GM dealer will replace suspect lock nuts. This service will be performed for you at no charge. Because of service scheduling requirements, it is likely that your dealer will need your vehicle longer than the actual service correction time of approximately 90 minutes. What should you do? You should contact your GM dealer to arrange a service appointment as soon as possible. When scheduling your appointment, confirm with the dealer that they service Medium Duty Trucks. Do you have questions? If you have any questions or concerns that your dealer is unable to resolve, please contact the appropriate Customer Assistance Center at the number listed below. For the hearing or speech impaired, please contact our Customer Assistance Center using the Telecommunication Relay Service by dialing 711 then providing the appropriate Customer Assistance Center number for your vehicle. Division Number Text Telephones (TTY) Chevrolet 1-800-222-1020 711 / 1-800-833-2438 Puerto Rico – English 1-866-467-9700 Puerto Rico – Español 1-866-467-9700 Virgin Islands 1-866-467-9700 If after contacting your dealer and the Customer Assistance Center, you are still not satisfied we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE, Washington, DC 20590, or call the toll-free Vehicle Safety Hotline at 1.888.327.4236 (TTY 1.800.424.9153), or go to http://www.nhtsa.gov. The National Highway Traffic Safety Administration Campaign ID Number for this recall is 22V874. Federal regulation requires that any vehicle lessor receiving this recall notice must forward a copy of this notice to the lessee within ten days. Product Safety Recall N222391080 Defective Suspension Nuts Page 6 of 6 Regina A. Carto Vice President Global Product Safety and Systems GM Recall: N222391080

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IMPORTANT SAFETY RECALL February 2022 This notice applies to your vehicle, VIN: __________________________________ Dear General Motors Customer: This notice is sent to you in accordance with the National Traffic and Motor Vehicle Safety Act. General Motors has decided that a defect which relates to motor vehicle safety exists in certain 2021 – 2022 model year Chevrolet Silverado Medium Duty 4500HD/5500HD/6500HD vehicles. As a result, GM is conducting a safety recall. We apologize for this inconvenience. However, we are concerned about your safety and continued satisfaction with our products. IMPORTANT • Your vehicle is involved in GM recall N222391080. • Schedule an appointment with your GM dealer. • This service will be performed for you at no charge. Why is your vehicle being recalled? Navistar, the manufacturer of these vehicles, has determined that certain hex flange lock nuts used in several locations in the suspension joints in these vehicles were not properly formed and heat treated by its supplier. Improperly manufactured nuts can result in a loss of joint tension over time. A loss of tension in the suspension joints may increase the risk of a crash. What will we do? Your GM dealer will replace suspect lock nuts. This service will be performed for you at no charge. Because of service scheduling requirements, it is likely that your dealer will need your vehicle longer than the actual service correction time of approximately 90 minutes. What should you do? You should contact your GM dealer to arrange a service appointment as soon as possible. When scheduling your appointment, confirm with the dealer that they service Medium Duty Trucks. Do you have questions? If you have questions or concerns that your dealer is unable to resolve, please contact the appropriate Customer Assistance Center at the number listed below. Division Number Text Telephones (TTY) Chevrolet 1-800-630-2438 1-800-833-2438 Puerto Rico – English 1-800-496-9992 Puerto Rico – Español 1-800-496-9993 Virgin Islands 1-800-496-9994 For the hearing or speech impaired, please contact our Customer Assistance Center using the Telecommunication Relay Service by dialing 711 then providing the appropriate Customer Assistance Center number for your vehicle. If after contacting your dealer and the Customer Assistance Center, you are still not satisfied we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., Washington, DC 20590, or call the toll-free Vehicle Safety Hotline at 1.888.327.4236 (TTY 1.800.424.9153), or go to http://www.nhtsa.gov. The National Highway Traffic Safety Administration Campaign ID Number for this recall is 22V874. Federal regulation requires that any vehicle lessor receiving this recall notice must forward a copy of this notice to the lessee within ten days. Regina Carto Vice President Global Vehicle Safety and Systems GM Recall: N222391080

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GLOBAL SAFETY FIELD INVESTIGATIONS DCS6463 URGENT – DISTRIBUTE IMMEDIATELY Date: February 23, 2023 Subject: REVISION: N222391080 – Safety Recall Defective Suspension Nuts Revised Service Procedure Models: 2021 – 2022 Chevrolet Silverado 4500HD/5500HD/6500HD To: All General Motors Medium Duty Dealers This bulletin is being revised to update the Service Procedure. Please discard all previous copies of N222391080. END OF MESSAGE GLOBAL SAFETY FIELD INVESTIGATIONS

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GLOBAL SAFETY FIELD INVESTIGATIONS DCS6424 URGENT – DISTRIBUTE IMMEDIATELY Date: January 27, 2023 Subject: N222391080 – Safety Recall Defective Suspension Nuts Models: 2021 – 2022 Chevrolet Silverado 4500HD/5500HD/6500HD To: All General Motors Medium Duty Dealers General Motors is releasing Safety Recall N222391080 today. The total number of U.S. vehicles involved is approximately 5,860. Please see the attached bulletin for details. Vehicles involved in this recall were placed on stop delivery November 23, 2022. Once the service procedure contained in the bulletin has been performed on the vehicle, the vehicle is released from stop delivery and the vehicle can be delivered to the customer. Frequently Asked Questions Document (FAQs) Attached to this message you will find a document that addresses the ten most likely questions customers may have regarding this Safety Recall. Please use this information as an aid to confidently answer customer concerns. Working Capital Assistance Program (WCAP) Eligibility Vehicles which were in dealer inventory at the time of this bulletin release were eligible for WCA. Please refer to the attached bulletin and GlobalConnect Message GCUS-9-9188 for additional information. Customer Letter Mailing The customer letter mailing will begin in February 2023. Global Warranty Management (GWM) The Required Field Action section on the Investigate Vehicle History (IVH) screen will be updated January 27, 2023. A list of vehicles in dealer inventory is attached to this message. Please hold all warranty transactions until IVH has been updated. END OF MESSAGE GLOBAL SAFETY FIELD INVESTIGATIONS

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