Brake Signal: Description and Operation

Anti-lock Brake Signal Circuit:

Purpose
On units equipped with all wheel drive the ECM controls the idle air control motor in response to the ABS signal--to ensure effective ABS operation.
- When the motor relay is activated, the ABS control unit turns ON the power transistor, short circuiting the terminal to ground. This causes the anti-lock braking signal to go from high to low.

Operation
The engine ECM provides the ABS control module with a 5 Volt reference signal. The engine ECM monitors this signal. When the ABS control module determines that brake control is needed, the ABS control module completes the ground circuit from the engine ECM. When this voltage drop is detected by the engine ECM. The ECM operates the idle speed control servo to provide effective anti-lock braking.