Theory Of Operation

The Powertrain Control Module (PCM) monitors the vehicle braking via the Stop Lamp Switch. For accuracy, the PCM monitors two separate brake switch signals. The operating mode of these signals are as follows:

Brake Switch Signal 1 operation:  The PCM sends out a 12 Volt, low amperage signal, which may not illuminate a test light, on the (B15) Brake Switch 1 circuit. The PCM monitors the voltage on this circuit to indicate if the brake pedal is depressed or released. When the brake pedal is released, the (B15) Brake Switch 1 circuit is connected to the (Z914) ground circuit and the PCM reads Zero Volts on the (B15) Brake Switch 1 circuit. When the pedal is pressed, the path to ground is broken and the PCM reads 12 Volts on the (B15) Brake Switch 1 circuit.

Brake Switch Signal 2 operation:  12 Volts are sent on the (F941) Ignition Switch Start/Run circuit through the Stop Lamp Switch to the PCM on the (B16) Brake Switch 2 circuit. The PCM monitors the voltage on this circuit to indicate if the brake pedal is depressed or released. Zero Volts on the (B16) Brake Switch 2 circuit indicates to the PCM that the pedal is pressed, and 12 Volts indicate that the brake pedal is released.