If Lamps Fails To Light, Inspect For:

A broken or disconnected wire at the switch
A Defective switch
A burned out Light Emitting Diode (LED)
A damaged circuit board

NOTE:

The LED's are soldered to, and part of, the Cab Compartment Node (CCN) electronic circuit board. If either the circuit board or any of the LED's are damaged or inoperative the entire CCN must be replaced.

To test the service brake warning system, refer to BASE BRAKES - SERVICE INFORMATION or ANTILOCK BRAKE SYSTEM (ABS) - SERVICE INFORMATION for Brakes, Diagnosis and Testing, Base Brake System Diagnosis Charts, Red Brake Warning Lamp.