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Service bulletins for the 2021 Mack LR

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.

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

By type

By component

By trouble code

Only bulletins with component: Engine are shown. Show all

Bulletins, newest first
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 2171-11 2025112025-12-03. Service bulletin. ENGINE; ELECTRICAL SYSTEM. CBR - Mack Temperature Sensor Troubleshooting Guide
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 170-8 2025052025-06-02. Service bulletin. ENGINE. Inactive Code P25AE00 Being Generated After A Hard Pull And A Momentary Drop In Engine Oil Pressure (Low Oil Pressure) (Possible Related Codes - SPN4811 , SPN 100 , PID 100)
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-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-2263 2024102024-11-04. Service bulletin. ENGINE. CBR - Mack Chassis - Timing Gear Plate Repair
CBR-561 2024082024-09-04. Service bulletin. ENGINE. CBR: 11L, 13L, And 16L Engine Oil Analysis Specifications - US10 And Newer Emissions
CBR-523 2024082024-09-04. Service bulletin. ENGINE. CBR: Overhead Wear Overview - Model Year2018 To Current (Common Rail Fuel System ONLY)
CBR-2139 2024052024-06-04. Service bulletin. FUEL/PROPULSION SYSTEM; ENGINE. CBR: Vehicles built with an 11 liter engine may experience a complaint of excessive fuel in the oil. It is possible that the source of the fuel is the rear fuel galley plug in the cylinder head. A new and improved fuel galley plug has been developed to resolve this issue.
CBR-2013 2024042024-05-01. Service bulletin. ENGINE AND ENGINE COOLING. CBR: Turbo Compound (TC) Hot Side Noise, Diagnostic Information.
CBR-2139 2024032024-04-02. Service bulletin. ENGINE AND ENGINE COOLING. CBR: Vehicles built with an 11 liter engine may experience a complaint of excessive fuel in the oil. It is possible that the source of the fuel is the rear fuel galley plug in the cylinder head.
CBR-2320 2023122024-01-03. Service bulletin. ENGINE AND ENGINE COOLING. CBR: For vehicles equipped with an 11L engine, the plastic saddle bracket holding the a/c line on the left side of the engine may move excessively and rub the area where it secures the line.
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
CBR-2131 2023082023-09-06. Service bulletin. ENGINE AND ENGINE COOLING; ELECTRICAL SYSTEM. CBR: Intermittent Diagnostic Trouble Codes U02A3,U029D, U029E - USE FOR NEW VEHICLES (US21+OBD22 Emissions)
CBR-2112 2023072023-08-02. Service bulletin. ELECTRICAL SYSTEM; POWER TRAIN; ENGINE AND ENGINE COOLING. CBR: Programming Failure - Chassis With Cummins Engine And An Allison Transmission
CBR-2303 2023072023-08-02. Service bulletin. ENGINE AND ENGINE COOLING:EXHAUST SYSTEM; ENGINE AND ENGINE COOLING. CBR: Mack DEF Dosing Valve Diagnostic Trouble Codes (DTC) P202D00, P208E00, P103B00 - US10+OBD13 And Newer Emissions
KC-22892023-07-06. Service bulletin. ENGINE AND ENGINE COOLING. Diagnostic Trouble Code (DTC) P103200: Particulate Matter Sensor Removed from Exhaust - US21+OBD22 Emissions
KC-2043 Rev 42023-07-06. Service bulletin. ENGINE AND ENGINE COOLING:ENGINE:ENGINE CONTROL MODULE (ECU/ECM); ELECTRICAL SYSTEM. Engine Control Module (EMS) Software (MSW) Information - Improvement List, Through June 2023 - US21+OBD2020 Emissions
KC-2116 Rev 92023-07-06. Service bulletin. ENGINE AND ENGINE COOLING. Mack NOx Sensor Troubleshooting Guide - US10+OBD13 And Newer Emissions
KC-2116 Rev 82023-07-06. Service bulletin. ENGINE AND ENGINE COOLING. Mack NOx Sensor Troubleshooting Guide - US10+OBD13 And Newer Emissions
KC-2158 Rev 62023-07-06. Service bulletin. ENGINE AND ENGINE COOLING; ELECTRICAL SYSTEM; ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:EMISSION CONTROL. CBR - Mack Selective Catalytic Reduction (SCR) Muffler Troubleshooting Guide - US10+OBD13 And Newer Emissions
KC-20502023-06-05. Service bulletin. ENGINE AND ENGINE COOLING. CBR: Diagnostic Trouble Code (DTC) P225C00 : NOx1 Sensor Stuck High - US17+OBD2019 And Newer Emissions
KC-2263-Ver52023-06-05. Service bulletin. ENGINE AND ENGINE COOLING. CBR: Timing Gear Plate Repair. This solution provides supplementary information to be used when installing a Timing Gear Plate with Integrated Seal.
KC-22692023-05-02. Service bulletin. ENGINE AND ENGINE COOLING. CBR: 11L Engines, Non-Common Rail - Air Compressor Coolant Pipe, Parts Substitution - US14+OBD13 To US14+OBD16

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