Brake lamp switch. Red brake warning lamp

Brake lamp switch

The brake lamp switch can be tested with an ohmmeter.

The ohmmeter is used to check continuity between the pin terminals (Fig. 4).

SWITCH CIRCUIT IDENTIFICATION

• Terminals 1 and 2: brake lamp circuit
• Terminals 3 and 4: RWAL/ABS module and Powertrain Control Module (PCM) circuit
• Terminals 5 and 6: speed control circuit

Fig. 4 Brake Lamp Switch Terminal Identification

1 - TERMINAL PINS

2 - PLUNGER TEST POSITIONS

SWITCH CONTINUITY TEST

NOTE: Disconnect switch harness before testing switch continuity.

With switch plunger extended, attach test leads to pins 1 and 2. Replace switch if meter indicates no continuity.

With switch plunger retracted, attach test leads to pins 3 and 4. Replace switch if meter indicates no continuity.

With switch plunger retracted, attach test leads to pins 5 and 6. Replace switch if meter indicates no continuity.

Red brake warning lamp

The red warning lamp is in circuit with the parking brake switch and pressure differential switch in the combination valve.

The red lamp illuminates when the parking brakes are applied, or when a pressure drop occurs in the front or rear brake hydraulic circuit.

The lamp illuminates for approximately 2-4 seconds at every engine start up. This is a self test feature designed to check bulb and circuit operation.

A pressure drop in the front or rear brake hydraulic circuit activates the pressure differential valve inside the combination valve. A pressure decrease moves the valve toward the low pressure side. As the valve moves, it pushes the pressure differential switch contact plunger upward. This closes the switch internal contacts and completes the circuit to the red warning lamp. The lamp will remain on until repairs are made and normal fluid pressure restored.