Parking Brake Indicator Light

[CROW]

Truck is an 05 dually with a six speed. The parking brake works as it should. Since the truck has a manual transmission, I apply the parking brake each time the truck is parked. However, the indicator light on the dash will not work. When the key is first turned on, a steady "BRAKE" light will come on whether or not the parking brake is applied, but will go off in a few seconds whether or not the parking brake is applied or not. Checked the switch on the left kick panel that the parking brake arm activates and it is a very simple deal and it appeared to be OK. It makes and breaks connection as it should. There is a single wire that attaches to the switch and it had just over 11 volts coming to it. I'm lost and any help would be appreciated.

 

[sag2]

Ground the wire and the voltage should go to zero. The cluster should also turn on the brake light.

 

[sag2]

A brake indicator is standard equipment on all instrument

clusters. This indicator is located near the lower

edge of the instrument cluster, between the tachometer

and the speedometer.

The brake indicator consists of a stencil-like cutout of the word BRAKE and the International Control and Display

Symbol icon for Brake Failure in the opaque layer of the instrument cluster overlay. The dark outer layer of the

overlay prevents the indicator from being clearly visible when it is not illuminated. A red Light Emitting Diode (LED)

behind the cutout in the opaque layer of the overlay causes the indicator to appear in red through the translucent

outer layer of the overlay when it is illuminated from behind by the LED, which is soldered onto the instrument

cluster electronic circuit board. The brake indicator is serviced as a unit with the instrument cluster.

OPERATION

The brake indicator gives an indication to the vehicle operator when the parking brake is applied, when there are

certain brake hydraulic system malfunctions as indicated by a low brake hydraulic fluid level condition, or when the

brake fluid level switch is disconnected. The brake indicator can also give an indication when certain faults are

detected in the Antilock Brake System (ABS). This indicator is controlled by a transistor on the instrument cluster

circuit board based upon cluster programming, electronic messages received by the cluster from the Controller

Antilock Brake (CAB) over the Controller Area Network (CAN) data bus, and a hard wired input from the park brake

switch.

The brake indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and

that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the

fused ignition switch output (run-start) circuit. Therefore, the LED will always be OFF when the ignition switch is in

any position except ON or START. The LED only illuminates when it is provided a path to ground by the instrument

cluster transistor. The instrument cluster will turn ON the brake indicator for the following reasons:

² Bulb Test - Each time the ignition switch is turned to the ON position the brake indicator is illuminated for

about four seconds as a bulb test. The entire bulb test is a function of the CAB.

² Brake Lamp-ON Message - Each time the cluster receives a lamp-ON message from the CAB, the brake

indicator will be illuminated. The CAB can also send brake lamp-ON messages as feedback during ABS diagnostic

procedures. The indicator remains illuminated until the cluster receives a lamp-OFF message from the

CAB, or until the ignition switch is turned to the OFF position, whichever occurs first.

² Park Brake Switch Input - Each time the cluster detects ground on the park brake switch sense circuit (park

brake switch closed = park brake applied or not fully released) while the ignition switch is in the ON position,

the brake indicator flashes ON and OFF. The indicator continues to flash until the park brake switch sense

input to the cluster is an open circuit (park brake switch open = park brake fully released), or until the ignition

switch is turned to the OFF position, whichever occurs first.

² Actuator Test - Each time the instrument cluster is put through the actuator test, the brake indicator will be

turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the LED and

the cluster control circuitry.

The park brake switch on the park brake pedal mechanism provides a hard wired ground input to the instrument

cluster circuitry through the park brake switch sense circuit whenever the park brake is applied or not fully released.

The CAB continually monitors the ABS system circuits and sensors, including the brake fluid level switch on the

brake master cylinder reservoir, to decide whether the system is in good operating condition. The CAB then sends

the proper lamp-ON or lamp-OFF messages to the instrument cluster. If the CAB sends a lamp-ON message after

the bulb test, it indicates that the CAB has detected a brake hydraulic system malfunction or that the ABS system

has become inoperative. The CAB will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.

For further diagnosis of the brake indicator or the instrument cluster circuitry that controls the LED, (Refer to 8 -

ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). The park brake switch input to the instrument

cluster can be diagnosed using conventional diagnostic tools and methods. Refer to the appropriate wiring

information. For proper diagnosis of the brake fluid level switch, the ABS, the CAB, the CAN data bus, or the electronic

message inputs to the instrument cluster that control the brake indicator, a diagnostic scan tool is required.

Refer to the appropriate diagnostic information.

 

[PFranzese]

Even a parking brake indicator light is complicated on these trucks!!!

 

[CROW]

SAG2--Appreciate your detailed response to my question. These trucks are complicated to us amateurs. Well done. I ran the instrument cluster check and found no codes. Again, thanks.