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Service bulletin SU2105

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 id10201621
Published by NHTSA2021-09-28
Manufacturer's numberSU2105
Manufacturer's date2021-05-18
NHTSA componentELECTRICAL SYSTEM

NHTSA's summary

The intent of Service Update SU2105 is to provide service notification of a running product improvement part change to the relay used for diesel exhaust fluid (DEF) line heaters. The new DEF line heater relay will be "Diode Suppressed". The new relay change is being made to improve circuit fault diagnostic capabilties. This change implements two new diode suppressed relay part numbers based on bus model application. The new relays are easily distinguishable by color. They have a yellow high temp tape wrap. Models Affected: Vision (BBCV), All American, and TX4 (T3FE, T3RE), with EPA/CARB certified on highway Cummins® Diesel Engine Features Built After 07/26/2021 Subject: The intent of Service Update SU2105 is to provide service notification of a running product improvement part change to the relay used for diesel exhaust fluid (DEF) line heaters. Information: The new DEF line heater relay will be "Diode Suppressed". The new relay change is being made to improve circuit fault diagnostic capabilities. This change implements two (2) new diode suppressed relay part numbers based on Blue Bird bus model application. The new relays are easily distinguishable by color. They have a yellow high temp tape wrap. New Diode Suppressed Relay Type, Part Number, And Application: Diode Suppressed “Micro Relay” 10073451 – All American and TX4 (T3FE, T3RE) with Cummins Diesel Engine Features Built After 07/26/2021 Diode Suppressed “Mini Relay” 10073452 – Vision (BBCV) with Cummins Diesel Engine Features Built After 07/26/2021

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

Electrical system

Vehicles listed
BLUE BIRD ALL AMERICAN SCHOOL BUS2022
BLUE BIRD ALL AMERICAN TRANSIT BUS2022
BLUE BIRD VISION SCHOOL BUS2022
BLUE BIRD VISION TRANSIT BUS2022

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