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Service bulletins for the 2021 Mack MD

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

112 on file from NHTSA, as of 2026-10-19.

By type

By component

By trouble code

Bulletins, newest first
CBR 2573-1 2026042026-05-05. Service bulletin. POWER TRAIN. CBR - Mack Chassis - Through Shaft Bearing Retainer Breakage On Mack Carriers.
CBR 2362-3 2026042026-05-04. Service bulletin. POWER TRAIN. CBR - Mack Carrier Nut Adhesive Change.
TSB M-432-002A 0320262026-04-02. Service bulletin. POWER TRAIN. TSB - Cable, Gear Selector, Replacement
CBR 2712-7 0320262026-04-02. Service bulletin. ELECTRICAL SYSTEM; UNKNOWN OR OTHER. CBR - No Start Condition After Over the Air Programing.
CBR 2107-22 2026012026-02-02. Service bulletin. ENGINE. CBR - Mack DEF Level (UQLS) Sensor Troubleshooting Guide - US17+OBD16 Emissions to US22+OBD2023 (DOES NOT APPLY TO AN(4) and PR(4)).
CBR 2172-5 0820252025-09-02. Service bulletin. ELECTRICAL SYSTEM. CBR - When an OTA (Over-The-Air) job starts to program the VECU blocks the starter relay out, if the job ends in a Critical failure, the vehicle will remain in Safe State.
CBR 407 0720252025-08-04. Service bulletin. SERVICE BRAKES; ELECTRICAL SYSTEM. CBR - To correct the MID136 SID 66 FMI 7 fault code the latest Bendix VCP file will need to downloaded.
CBR 2488 0720252025-08-04. Service bulletin. ELECTRICAL SYSTEM. CBR - A significant GPS reporting issue is affecting fleet operations, with trucks maintaining back-office communication but failing to transmit GPS location data.
CBR 2107-21 2025052025-06-02. Service bulletin. FUEL/PROPULSION SYSTEM; ENGINE. Mack DEF Level (UQLS) Sensor Troubleshooting Guide - US17+OBD16 Emissions and Newer
CBR 445- 11 2025052025-06-02. Service bulletin. FUEL/PROPULSION SYSTEM. Vehicles Equipped With a Common Rail Fuel System - Aftermarket Secondary Fuel Filters, Important Information On Approved Filters - US17+OBD16 toUS21+OBD23
CBR-561 2025032025-04-02. Service bulletin. ENGINE. If oil dilution is suspected refer to the applicable CBR solution below: ∙ CBR-659􀁡Mack Chassis - Oil Diluted With Fuel; Fuel In Oil, Diagnostic Information - All Emissions, All Model Years
CBR-2016 2024122025-01-02. Service bulletin. SUSPENSION. Frame lean can be caused by several seemingly isolated possibilities. The two most common are suspension and frame assembly issues.
CBR-997 2024112024-12-02. Service bulletin. ENGINE. Vehicles may present with oil leak coming from the clutch/flywheel housing and observation of burned clutch smell or clutch slipping. These symptoms can be mistaken as a crankshaft rear main seal leak, when the actual cause is the crankshaft adaptor O-ring.
CBR-407 2024092024-10-03. Service bulletin. SERVICE BRAKES. CBR: To correct the MID136 SID 66 FMI 7 fault code the latest Bendix VCP fi le will need to be downloaded.
CBR-2350 2024072024-08-01. Service bulletin. ELECTRICAL SYSTEM. CBR: Telematics Gateway (TGW) Connect Ability Issues
CBR-2013 2024042024-05-01. Service bulletin. ENGINE AND ENGINE COOLING. CBR: Turbo Compound (TC) Hot Side Noise, Diagnostic Information.
CBR-1008 2024042024-05-01. Service bulletin. POWER TRAIN. CBR: Equipped With An Automated Manual Transmission Model D or F ( AMT-D, AMT-F, mDrive) Missing X1 Value In VDA And Default Settings Guidelines, ParameterP1AOB; Fault Code P1052-54, Error 40,Or Error 18 Encountered During Clutch Or Tran.
M-834-001 2024012024-02-02. Service bulletin. ELECTRICAL SYSTEM. TSB: Some Mack MMD trucks could experience an issue with the ignition lock cylinder sticking. Trucks that experience a sticking lock cylinder could have a lock cylinder that becomes tight or sticks in the start position. If the above condition is found replace the ignition lock cylinder.
CBR-2342 2024012024-02-02. Service bulletin. SUSPENSION. CBR: Mack Medium Duty (MMD) Rear Suspension Bump Stop Bending
CBR-2333 2024012024-02-02. Service bulletin. ELECTRICAL SYSTEM. CBR: TGW Will Not Connect After SIM Card Replacement
CBR-2016 2024012024-02-02. Service bulletin. STRUCTURE; SUSPENSION. CBR: Frame Or Cab Lean
M-465-001 2023112023-12-05. Service bulletin. POWER TRAIN. TSB: Mack Trucks now offer an improved HD Inter-Axle Through Shaft for the CRD 125, 150, 180, and 200 family carriers. The new HD shaft went into production on January 23rd, 2023 for 2.54 - 3.50 axle ratios and April 1st, 2023 for 3.56 - 3.98 ratios. The new HD through shaft is an upgrade over the current standard shaft and can now be used as a replacement part instead of the standard shaft. The new HD shaft has a new design to increase strength, longevity and life over the standard shaft.
M-258-014 2023092023-10-03. Service bulletin. ENGINE AND ENGINE COOLING:ENGINE:DIESEL; ENGINE AND ENGINE COOLING. TSB: Aftertreatment Diesel Exhaust Fluid (DEF) Tank, Level Sensor, Replacement
M-258-012 2023092023-10-03. Service bulletin. ENGINE AND ENGINE COOLING; FUEL SYSTEM, DIESEL:DELIVERY:PRESSURE SENSOR; ENGINE AND ENGINE COOLING:ENGINE:DIESEL. TSB: Aftertreatment Diesel Exhaust Fluid (DEF) Tank, Level Sensor, Replacement
M728-005A 2023082023-09-06. Service bulletin. SUSPENSION. TSB: Barksdale Leveling Valve, Leak Test

The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.