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C1AB4 on the 2018 Toyota Sequoia

The bulletins listed name this code in NHTSA's summary, or are about the same components. A bulletin or a recall listed here may apply to the model year. None of it is a diagnosis.

This code is specific to a manufacturer and is not described here. Its meaning is in the manufacturer's service information.

Bulletins for this model year that name C1AB4
T-SB-0021-18_Rev2018-07-16. Service bulletin. TSB: REVISION NOTICE June 12, 2018 Rev1: ? The Production Change Information section has been updated. Any previous printed versions of this bulletin should be discarded. Some 2018 model year Sequoia vehicles equipped with Blind Spot Monitor (BSM) and auto-dimming mirrors may exhibit a BSM warning message in the combination meter immediately after engine startup and an inoperative BSM system with Diagnostic Trouble Codes (DTCs) C1AB4 (Open in Outer Mirror Indicator [Master]) or C1AB5 (Open in Outer Mirror Indicator [Slave]). Follow the Repair Procedure in this bulletin to address this condition.

1 on file from NHTSA, as of 2026-10-19. See them in the bulletin list. A bulletin lists model years: read the document for which vehicles it concerns.