Transmission Control Switch (TCS) & Indicator Lamp (TCIL)

DESCRIPTION
The transmission control switch (TCS) is a momentary contact switch. When this switch is pressed, a signal is sent to the powertrain control module. The powertrain control module then energizes the transmission control indicator lamp (TCIL) and toggles Solenoid 3 (SS3), applying the forward clutch to provide engine braking and canceling fourth gear operation.

TRANSMISSION CONTROL SWITCH (TCS) FAILURE
Symptoms:
No overdrive cancel when switch is cycled.
DTC:
P1780, tested during Key ON Engine OFF (KOEO) On-Board Diagnostic only.

TRANSMISSION CONTROL INDICATOR LAMP (TCIL) FAILURE
Description:
Transmission Function: Indicates overdrive cancel mode activated (lamp ON) and monitored sensor failures (lamp FLASHING).
Symptoms:
- Failed "ON" - Overdrive cancel mode always indicated, no flashing for monitored sensor failures.
- Failed "OFF" - Overdrive cancel mode never indicated, no flashing for monitored sensor failures.