4WD Switch: Description and Operation

Brake And 4WD Switch Circuits:

The T-Series truck has a switch mounted in the front axle drive train that is open in 2WD mode and closed in 4WD mode. This switch is part of an indicator light circuit and is mechanically operated by the movement of a shift mechanism linkage within the transfer case. The ECU will change its antilock braking program when it sees a signal (12 volts) that the front axle is in 4WD mode. The signal is less than 1 volt when the brake switch contacts are open.

The ECU does not monitor the 4WD switch circuit for conditions.