RAM 3500 HD Truck 2WD L6-6.7L DSL Turbo (2008)
Traction Control Indicator Lamp: Description and Operation
Electronic Stability Program/Brake Assist System Indicator
Description
DESCRIPTION
An Electronic Stability Program/Brake Assist System (ESP/BAS) indicator is only found in the instrument clusters for vehicles equipped with a gasoline
engine. However, on vehicles not equipped with the optional ESP/BAS, this indicator is electronically disabled. This indicator is located in the lower
portion of the tachometer dial face in the instrument cluster overlay.
The ESP/BAS indicator consists of a stencil-like cutout of the text ESP BAS 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. An amber Light Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the indicator to appear in amber 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 ESP/BAS indicator is serviced as a unit with the instrument cluster.
Operation
OPERATION
The ESP/BAS indicator gives an indication to the vehicle operator when a problem has been detected in the Electronic Stability Program (ESP)/Brake
Assist System (BAS). This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic
messages received by the cluster from the Controller Antilock Brake (CAB) and the Totally Integrated Power Module (TIPM) over the Controller Area
Network (CAN) data bus.
The ESP/BAS 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 ESP/BAS indicator for the following reasons:
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Bulb Test - Each time the ignition switch is turned to the ON position the ESP/BAS indicator is illuminated for about four seconds as a bulb test.
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ESP/BAS Indicator Lamp-On Message - Each time the cluster receives an electronic ESP/BAS indicator lamp-ON message from the CAB or
the TIPM, the ESP/BAS indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the
CAB or TIPM, or until the ignition switch is turned to the OFF position, whichever occurs first.
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Actuator Test - Each time the cluster is put through the actuator test, the ESP/BAS 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 CAB and TIPM continually monitor the ESP/BAS system circuits and sensors to decide whether the system is in good operating condition and the
proper outputs to the components of the system. The CAB or TIPM then sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical
Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).
