Ford B166a60 -

If the mirror glass passes the resistance test, the issue is on the vehicle side. Keep the glass disconnected, start the vehicle's engine, and engage the rear window defrost button. Set your multimeter to and measure across the two wire terminals inside the mirror housing.

: Constant opening and closing of the car door stresses the wiring loom inside the rubber boot, fracturing internal copper strands.

A: Yes, the vehicle is mechanically safe to drive. However, the passenger airbag may not deploy, making it unsafe for front-seat passengers. ford b166a60

In most cases, this code is triggered when the vehicle's computer detects that a component—frequently the or blind spot sensors —is not communicating correctly with the Body Control Module (BCM). Common Causes of the B166A60 Error

: A failure subtype indicating an event-based signal failure, typically an open circuit . Primary Causes The most frequent reasons for this fault include: If the mirror glass passes the resistance test,

Turn your vehicle’s ignition to the "ON" position and press the rear defrost/heated mirror button on your climate control dash. Set your multimeter to DC Volts and measure across the two loose wire connectors inside the mirror housing:

: Corroded, pinched, or broken wires in the door harness or within the mirror assembly. : Constant opening and closing of the car

: Once the repair is complete, you can clear the code using an OBD-II scanner or by disconnecting the battery for approximately 15 minutes.

: Ford is providing a free Over-the-Air (OTA) software update to resolve the communication error. 3. Pillar Post Covers

: Affects interior or exterior cabin features rather than engine performance.

The most frequent failure point is the microscopic resistive grid glued behind the mirror glass. Constant heating and cooling cycles, combined with moisture intrusion, cause these thin circuits to crack and fail over time.