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Service bulletins for the 2021 Western Star 4900

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.

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

By type

By component

Bulletins, newest first
20TS-07REV2021-03-01. Service bulletin. ENGINE AND ENGINE COOLING. Revised Technical Service Letter for Cold Weather Faults on GHG17/21 DD13 with MCM Software Version 14. Due to colder weather, there may be an increase in the frequency of faults, noted below, on GHG17/21 DD13 trucks built after June 5th 2019. This is due to a calibration issue in the current MCM software (14.1.1.5 or 14.2.1.3). New software is scheduled for release in the first quarter of 2021 that will address these faults.
WP60-1002021-02-27. Service bulletin. EQUIPMENT. Western Star Parts Technical Bulletin for Universal Design Floor Mats. Universal floor mat designs fit multiple cab configurations and may require trimming. Trim lines displaying size options are scored into the pad side of the mat; use an existing floor mat as a guide for optimal results. The new mat should not interfere with safety-critical equipment, such as foot pedals.
ICI21-0032021-02-26. Service bulletin. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL. Superseding Letter to an Important Campaign Information Letter to announce a reimbursement available to dealers for travel to a customer's location to perform a recall or field service campaign. Potential travel reimbursement applies to DTNA truck dealers and Detroit Diesel distributors. Thomas Built Buses will be addressed separately. This letter supersedes ICI20-022R.
WI21-0062021-02-26. Service bulletin. ELECTRICAL SYSTEM; ENGINE AND ENGINE COOLING; EQUIPMENT ADAPTIVE/MOBILITY; EQUIPMENT. Warranty Information Letter for Detroit NOx Sensor Circuit Fault Codes - Claim Guidelines.
WI21-0052021-02-25. Service bulletin. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL; EQUIPMENT. Warranty Information Letter for Body Builder/Truck Equipment Manufacturer Demonstration Program.
WI20-014R2021-02-25. Service bulletin. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL. Revised Warranty Information Letter for OWL and Warranty Manual Improvement: Sublets and Travel Time/Distance. In the spirit of continuous improvement, DTNA reviewed sublet-related policies and procedures. The goal was to improve language clarity and optimize processes. Revisions are in blue font.
TechTalk80442021-02-03. Service bulletin. ELECTRICAL SYSTEM; ENGINE AND ENGINE COOLING. Tech Talk discussion on Western Star No Start.
21TS-012021-01-28. Service bulletin. EQUIPMENT; ENGINE AND ENGINE COOLING. Technical Service Letter for Detroit Bearing Failures - Standard Diagnostic Times. DTNA is increasing repair strategies for determining the root cause of Detroit DD heavy duty lower end bearing failures. To support this strategy change, Detroit now has two (2) Standard Diagnostic Times (SDTs), easy and difficult, which can be applied to repair orders.
WI21-0032021-01-28. Service bulletin. EQUIPMENT; ENGINE AND ENGINE COOLING; EQUIPMENT ADAPTIVE/MOBILITY. Warranty Information Letter for Detroit Bearing Failures - Standard Diagnostic Times. DTNA is increasing repair strategies for determining the root cause of Detroit DD heavy duty lower end bearing failures. To support this strategy change, Detroit now has two (2) Standard Diagnostic Times (SDTs), easy and difficult, which can be applied to repair orders.
SBW35-0182020-12-30. Service bulletin. POWER TRAIN. Western Star Service Bulletin for Axle Flange Gasket Replaced with O-Ring. Daimler Trucks North America has released a new axle shaft to hub rubber O-ring (part number 11-30728-000) as a replacement for the paper gasket (part number 11-14418-000). The new O-ring will provide better sealing and is reusable. It is quicker and easier to use compared to the paper gasket, because using a paper gasket requires cleaning the hub when the axle shaft is removed.
SBW42-0142020-12-22. Service bulletin. EQUIPMENT ADAPTIVE/MOBILITY; SERVICE BRAKES; EQUIPMENT. Western Star Service Bulletin for Access to Front Brake Zerk Fittings. Certain vehicles with Detroit front axles and Meritor EX-L front air disc brakes do not have access to the front brake zerk fittings for lubrication.
WP20-018R2020-12-12. Service bulletin. STEERING; POWER TRAIN. Revised Warranty Policy Letter for Alliance/Mascot Aftermarket Warranty and Claim Filing. Revisions are in blue. With Mascot now in partnership with Detroit Reman and Alliance Parts, DTNA is pleased to announce that Mascot coverage has been added to OWL. Remanufactured Alliance/Mascot parts include transmission, differential, steering gear, and steering pump used in an on-highway vehicle applications. The Alliance/Mascot aftermarket warranty coverage period has not changed: depending on the part, coverage is for one (1) or two (2) years and current parts, labor, and reimbursement policies apply.
WP20-0182020-12-12. Service bulletin. STEERING; EQUIPMENT ADAPTIVE/MOBILITY; EQUIPMENT; POWER TRAIN. Warranty Policy Letter for Alliance/Mascot Aftermarket Warranty and Claim Filing. With Mascot now in partnership with Detroit Reman and Alliance Parts, DTNA is pleased to announce that Mascot coverage has been added to OWL. Remanufactured Alliance/Mascot parts include transmission, differential, steering gear, and steering pump used in an on-highway vehicle applications. The Alliance/Mascot aftermarket warranty coverage period has not changed: depending on the part, coverage is for one (1) or two (2) years and current parts, labor, and reimbursement policies apply.
18SP7442020-12-08. Service bulletin. EQUIPMENT ADAPTIVE/MOBILITY; ENGINE AND ENGINE COOLING; FUEL SYSTEM, GASOLINE:FUEL INJECTION SYSTEM:FUEL RAIL. Special Publication letter for Two-Filter Fuel System KM59 GEN1 DD15 DD16 Severe Duty High Pressure Fuel Rail Feed Lines Service Kit.
20TS-092020-12-07. Service bulletin. ENGINE AND ENGINE COOLING. Technical Service Letter for SPN 3711 FMI 31 on GHG17 DD15 Trucks.
TechTalk79012020-12-03. Service bulletin. ELECTRICAL SYSTEM:WIRING; VISIBILITY. Tech Talk discussion on Delayed Wiper Response.
TechTalk77742020-11-03. Service bulletin. VISIBILITY; EQUIPMENT ADAPTIVE/MOBILITY; EQUIPMENT. Tech Talk discussion on SS 1034711 HADLEY MIRROR
20TS-072020-10-21. Service bulletin. ELECTRICAL SYSTEM:SOFTWARE; POWER TRAIN:AUTOMATIC TRANSMISSION:CONTROL MODULE (TCM/PCM/TECM); ENGINE AND ENGINE COOLING. Technical Service Letter for Cold Weather Faults on GHG17/21 DD13 with MCM Software Version 14. Due to colder weather, there may be an increase in the frequency of faults, noted below, on GHG17/21 DD13 trucks built after June 5th 2019. This is due to a calibration issue in the current MCM software (14.1.1.5 or 14.2.1.3). New software is scheduled for release in the first quarter of 2021 that will address these faults.
17TS-05REV22020-10-21. Service bulletin. POWER TRAIN; ELECTRICAL SYSTEM:SOFTWARE. Revised Technical Service Letter for Detroit DT12 TCM GHG17 Only; Bootloader Update. On Detroit DT12 equipped vehicles, it may be necessary to complete an additional step in the programming process when updating the TCM software.
SS1034783REV2020-10-19. Service bulletin. SUSPENSION. Revised Service Solution for 20K Detroit Axle King Pin Lube Access. Western Star trucks equipped with 20k Detroit front axles and disc brakes built up to 8/17/2020 do not have sufficient room to access the king pin grease zerk.
20TS-062020-10-13. Service bulletin. EQUIPMENT ADAPTIVE/MOBILITY; ENGINE AND ENGINE COOLING. DDC Technical Service Letter for GHG17 DD Platform Heavy Duty Oil Pan Drain Plug Inserts. Some GHG17 DD Platform Heavy Duty oil pans may experience an issue with the oil pan drain plug insert spinning during removal or installation while completing an oil change. Leaking may also be observed at the drain plug and/or other plugs in the oil pan.
SBW54-0762020-10-12. Service bulletin. EQUIPMENT; ELECTRICAL SYSTEM. Western Star Service Bulletin for Connecting the Chassis Harness Connector to the Cab Front Wall 104-Way Pass-Through Connector. This bulletin describes how the chassis harness connector functions and how to verify the four locks of the terminal stabilizer plate on the 104-way pass-through connector are in pre-stage position. The terminal stabilizer plate is the white plastic plate located inside the 104-way pass-through connector. The stabilizer plate floats up and down in the pass-through connector to protect the terminals from being damaged when the chassis harness connector is removed and connected.
18SP7362020-10-01. Service bulletin. ENGINE AND ENGINE COOLING:ENGINE:GASOLINE:BELTS AND ASSOCIATED PULLEYS; ENGINE AND ENGINE COOLING:COOLING SYSTEM:FAN. Detroit Diesel Special Publication informing about Heavy Duty Friction Style Belt Tensioner Kit. This heavy duty friction style belt tensioner kit contains the belt tensioner and two M10 bolts to correctly pin the friction style belt tensioner. The M10x80mm bolt is used to pin the engine cooling fan drive arm. The M10x50mm bolt is used to pin the engine accessory drive arm.
20TS-03REV22020-10-01. Service bulletin. ENGINE AND ENGINE COOLING. Revised Technical Service Letter for DD Heavy Duty Platform Belt Tensioner Change. A newly designed, dual-arm friction shoe damping tensioner was implemented for the DD Heavy Duty Platform. The revision includes additional information on retrofit and service kits.
TechTalk76792020-10-01. Service bulletin. ENGINE AND ENGINE COOLING. Tech Talk discussion on repair verification for codes like 'low air flow' when a trailer is not available.

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