Lamp Out Indicator: Description and Operation

CAUTION: Use of additional lights, external lights or improper relacement bulbs may result in false warning or no warning.


When the rear park lamps are energized, the Lamp Out Warning Module senses for a burned out rear park lamp filament, When a lamp out condition is detected, the Lamp Out Warning Module illuminates the REAR LAMP OUT Indicator in the Overhead Warning Indicator Display.

When the Lo Beam Headlamps are energized, the Lamp Out Warning Module senses for a burned out Lo Beam Headlamp filament. When a lamp out condition is detected, the Lamp Out Warning Module illuminates the HEADLAMP OUT Indicator in the Overhead Warning Indicator Display.

When the brakes are applied, the Lamp Out Warning Module senses for a burned out stop/turn lamp filament. When a lamp out condition is detected, the Lamp Out Warning Module illuminates the REAR LAMP OUT Indicator in the Overhead Warning Indicator Display.

To detect a lamp out condition, the vehicle incorporates a special body wiring harness containing several resistive wires. These resistive wires are used to feed the lamps being sensed, and their shunt voltages provide the inputs to the Lamp Out Warning Module. When the bulbs are operating correctly, the voltage drop across the resistive wires will provide approximately .5 volts to the Module. Note that the Module has been designed to sense one or two bulb systems only. In a two bulb system where only one bulb is operating, the input voltage will be approximately .25 volts. If both bulbs are out, the input voltage is 0. In a one bulb system, the input voltage is at approximately .5 volts if the bulb is operating. It is 0 volts if the bulb is not operating. These voltage differences are sensed by the Module and the outputs are set accordingly.

This system contains a bulb test feature. With the Ignition Switch in START, voltage is applied to the Lamp Out Warning Module, causing the indicator to light. The Module grounds the 130 (R/LG) and 135 (Y/R) wires.