Warning Lights
FIGURE 39-12
Warning lamp.

Warning lamps are usually part of the instrument cluster and are controlled by electronic control units in the vehicle on a modern vehicle. Warning lamps provide the vehicle operator with information regarding the operation of the main vehicle systems, such as the vehicle battery charge level, oil pressure level, and airbag system status Figure 39-12. When the ignition initially comes on, the warning lamps usually light up as part of a self-test to show that they are in working order. Once the engine starts, the warning lamps should extinguish and not come on again while the engine is running, unless there is a system fault. Some vehicles have warning lights that self-test while the vehicle is being cranked. This function is performed by the “proofing circuit” in the ignition switch, which grounds certain warning lights when turned to the “crank” position.