# 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 bulletins from NHTSA, as of 2026-10-19.

- [CBR 2573\-1 202604](/bulletins/11032092.md), 2026-05-05, Service bulletin: POWER TRAIN. CBR \- Mack Chassis \- Through Shaft Bearing Retainer Breakage On Mack Carriers.
- [CBR 2362\-3 202604](/bulletins/11032086.md), 2026-05-04, Service bulletin: POWER TRAIN. CBR \- Mack Carrier Nut Adhesive Change.
- [TSB M\-432\-002A 032026](/bulletins/11030591.md), 2026-04-02, Service bulletin: POWER TRAIN. TSB \- Cable, Gear Selector, Replacement
- [CBR 2712\-7 032026](/bulletins/11030579.md), 2026-04-02, Service bulletin: ELECTRICAL SYSTEM; UNKNOWN OR OTHER. CBR \- No Start Condition After Over the Air Programing.
- [CBR 2107\-22 202601](/bulletins/11028032.md), 2026-02-02, 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 082025](/bulletins/11022289.md), 2025-09-02, 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 072025](/bulletins/11021333.md), 2025-08-04, 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 072025](/bulletins/11021332.md), 2025-08-04, 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 202505](/bulletins/11018813.md), 2025-06-02, Service bulletin: FUEL/PROPULSION SYSTEM; ENGINE. Mack DEF Level \(UQLS\) Sensor Troubleshooting Guide \- US17\+OBD16 Emissions and Newer
- [CBR 445\- 11 202505](/bulletins/11018806.md), 2025-06-02, 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 202503](/bulletins/11016342.md), 2025-04-02, 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 202412](/bulletins/11012156.md), 2025-01-02, 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 202411](/bulletins/11010857.md), 2024-12-02, 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 202409](/bulletins/11008366.md), 2024-10-03, 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 202407](/bulletins/11005410.md), 2024-08-01, Service bulletin: ELECTRICAL SYSTEM. CBR: Telematics Gateway \(TGW\) Connect Ability Issues
- [CBR\-2013 202404](/bulletins/10253807.md), 2024-05-01, Service bulletin: ENGINE AND ENGINE COOLING. CBR: Turbo Compound \(TC\) Hot Side Noise, Diagnostic Information.
- [CBR\-1008 202404](/bulletins/10253804.md), 2024-05-01, 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 202401](/bulletins/10249557.md), 2024-02-02, 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 202401](/bulletins/10249556.md), 2024-02-02, Service bulletin: SUSPENSION. CBR: Mack Medium Duty \(MMD\) Rear Suspension Bump Stop Bending
- [CBR\-2333 202401](/bulletins/10249553.md), 2024-02-02, Service bulletin: ELECTRICAL SYSTEM. CBR: TGW Will Not Connect After SIM Card Replacement
- [CBR\-2016 202401](/bulletins/10249551.md), 2024-02-02, Service bulletin: STRUCTURE; SUSPENSION. CBR: Frame Or Cab Lean
- [M\-465\-001 202311](/bulletins/10246086.md), 2023-12-05, 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 202309](/bulletins/10243453.md), 2023-10-03, 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 202309](/bulletins/10243452.md), 2023-10-03, 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 202308](/bulletins/10241946.md), 2023-09-06, Service bulletin: SUSPENSION. TSB: Barksdale Leveling Valve, Leak Test

More: [the next page](/v1/vehicles/2021_mack_md/bulletins?cursor=2023-09-06_10241946) (JSON)

JSON: [/v1/vehicles/2021_mack_md/bulletins](/v1/vehicles/2021_mack_md/bulletins)

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