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Service bulletin 21NA237

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 id10205563
Published by NHTSA2021-12-27
Manufacturer's number21NA237
Manufacturer's date2021-11-18
NHTSA componentEQUIPMENT; ENGINE AND ENGINE COOLING:COOLING SYSTEM:HOSES/LINES/PIPING/FITTINGS

NHTSA's summary

THis technical bulletin provides a procedure to perform a cooling system flush to remove possible debris from the cooling system pipes.

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, Equipment and accessories, Cooling system

Vehicles listed
CADILLAC ESCALADE ESV2021
CADILLAC ESCALADE NA2021 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET 35002020
CHEVROLET 35002021
CHEVROLET SILVERADO 15002019, 2020, 2021 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SILVERADO 25002020, 2021 (the catalog's model; the bulletin names a series or trim of it)
CHEVROLET SUBURBAN2021
CHEVROLET TAHOE2021
GMC SIERRA 15002019, 2020, 2021 (the catalog's model; the bulletin names a series or trim of it)
GMC SIERRA 25002020, 2021 (the catalog's model; the bulletin names a series or trim of it)
GMC SIERRA 35002020, 2021 (the catalog's model; the bulletin names a series or trim of it)
GMC YUKON2021
GMC YUKON XL2021

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

Other bulletins for the same vehicles and component
22NA0132022-05-31. Service bulletin. This technical bulletin provides a procedure for the technician to check and tighten the CAC plumbing if found loose.
20NA1662022-05-31. Service bulletin. This informational bulletin advises the technician of possible coolant entering the areas of the engine, either through failed parts or defects in the castings, that may be the cause of the concerns related to the MIL or the engine running rough.
21NA2372022-02-14. Service bulletin. THis technical bulletin provides a procedure to perform a cooling system flush to remove possible debris from the cooling system pipes.
21NA2572021-12-27. Service bulletin. This service bulletin provides a service procedure to correct a customer concern of a Malfunction Indicator Lamp (MIL) Illuminated - DTC P3075 Set.
18NA1032020-11-30. Service bulletin. This service bulletin provides information to correct a customer concern of an in-tank fuel pump whining noise, engine hard to start and/or stalls and Malfunction Indicator Lamp (MIL) is illuminated.
PIT57892020-11-16. Service bulletin. This Preliminary information communicates an issues with an SES MIL and DTC P2B87 setting. Engineering is working on releasing updated BCM cals to correct the concern.
PIP5684B2020-08-10. Service bulletin. This Preliminary information communicates the use of air leak diagnostic test tool CH-52250 in addition to the information found in the service manual.
20NA0102020-06-22. Service bulletin. This technical bulletin provides a procedure to replace the cooling fan if found contacting the shroud causing the customers concern.
N192266750-022020-03-23. Service bulletin. Service Update - On vehicles that are equipped with a 6.6L diesel engine, may have one or more of the following conditions exist: 1. The instrument panel cluster may incorrectly display the message ?DEF Low? when a diesel exhaust fluid (DEF) controller internal fault is detected (DTC P20FF), instead of displaying the proper ?Service DEF System? message. 2. The customer may complain of excessive engine fan noise at a low vehicle speed. 3. Under certain conditions, the diagnostic system may set one of the following DTC?s when there is no problem with a component: (P20EE, P226D, P16F3 and P129F). Dealers are to reprogram the engine control module and perform NOx and Catalyst Resets and Regen Enable.
19NA1042019-07-29. Service bulletin. This informational bulletin provides information for dealers/technicians and customers on steam/vapor coming from the front grille or radiator area.