Transmission Control Indicator Lamp
WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2004 Mercury Sable, 2004 Mercury Mountaineer, 2004 Mercury Monterey, 2004 Mercury Marauder, and 2004 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.
The transmission control indicator lamp (TCIL) is an output signal from the PCM that controls the lamp on/off function depending on the engagement or disengagement of overdrive. Refer to TRANSMISSION CONTROL SWITCH in Hardware PCM Inputs.