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Service bulletin 21TS-06

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.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10191070
Published by NHTSA2021-05-01
Manufacturer's number21TS-06
Manufacturer's date2021-04-19
NHTSA componentENGINE AND ENGINE COOLING

NHTSA's summary

Detroit Technical Service Letter for Gen 5 DD15 Exhaust Valve Adjusting Screw Excessive Wear. Some Detroit Heavy Duty Gen 5 DD15 engines are experiencing exhaust valve bridges that fall out of position while running. The engine may experience conditions such as rough running, misfire, or popping out of the intake. Misfire or exhaust pressure fault codes may also be present. Excessive valve lash caused by a worn rocker arm adjusting screw foot results in the valve bridge falling off the exhaust valves.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Engine

Vehicles listed
FCCC FCCC
FREIGHTLINER FREIGHTLINER
STERLING STERLING
THOMAS BUILT BUSES THOMAS BUILT BUSES
WESTERN STAR WESTERN STAR

Listing a model year does not mean every vehicle of it is concerned: the document says which.