vides a ground input to the ElectroMechanical Instrument Cluster (EMIC) (also sometimes referred to as the Cab
Control Node/CCN) on a park brake switch sense circuit whenever the park brake is applied, and opens this circuit
whenever the park brake is released. The park brake switch sense input to the EMIC is used for control of the brake
indicator and may also be used as a logic input for other electronic features in the vehicle.
The park brake switch can be diagnosed using conventional diagnostic tools and methods. However, proper testing
of the EMIC processing of the park brake switch sense input requires the use of a diagnostic scan tool. Refer to the
appropriate diagnostic information.
DIAGNOSIS AND TESTING
PARK BRAKE SWITCH
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
NOTE: If the brake indicator stays on with the ignition switch in the On position and the park brake
released, or comes on while driving, the brake system must be diagnosed and repaired prior to performing
the following tests. (Refer to 5 - BRAKES - DIAGNOSIS AND TESTING). If no brake system problem is found,
the following procedures will help to locate a shorted or open park brake switch sense circuit, or a faulty
park brake switch.
INDICATOR ILLUMINATES DURING BULB TEST, BUT DOES NOT WHEN PARK BRAKE APPLIED
1. Disconnect and isolate the battery negative cable. Disconnect the body wire harness connector for the park
brake switch from the switch terminal. Apply the parking brake. Check for continuity between the park brake
switch terminal and a good ground. There should be continuity. If OK, go to Step 2. If not OK, replace the faulty
park brake switch.
2. Disconnect the instrument panel wire harness connector (Connector C1) for the instrument cluster from the clus-
ter connector receptacle. Check for continuity between the park brake switch sense circuit cavities of the body
wire harness connector for the park brake switch and the instrument panel wire harness connector for the instru-
ment cluster. There should be continuity. If not OK, repair the open park brake switch sense circuit between the
park brake switch and the instrument cluster as required.
INDICATOR REMAINS ILLUMINATED - BRAKE SYSTEM CHECKS OK
1. Disconnect and isolate the battery negative cable. Disconnect the body wire harness connector for the park
brake switch from the switch terminal. Check for continuity between the terminal of the park brake switch and a
good ground. There should be no continuity with the park brake released, and continuity with the park brake
applied. If OK, go to Step 2. If not OK, replace the faulty park brake switch.
2. Disconnect the instrument panel wire harness connector (Connector C1) for the instrument cluster from the clus-
ter connector receptacle. Check for continuity between the park brake switch sense circuit cavity of the body wire
harness connector for the park brake switch and a good ground. There should be no continuity. If not OK, repair
the shorted park brake switch sense circuit between the park brake switch and the instrument cluster as
required.
REMOVAL
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
HB
LAMPS/LIGHTING - EXTERIOR - SERVICE INFORMATION
8L - 115