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

DESCRIPTION
The Transmission Control Switch (TCS) is a momentary contact switch. When the switch is pressed, a signal is sent to the powertrain control module. The powertrain control module then energizes the transmission control indicator lamp and the coast clutch solenoid, applying the coast clutch to provide engine braking and cancels fourth gear operation. The TCIL indicates overdrive cancel mode activated (lamp on), electronic pressure control circuit shorted or monitored sensor failure (lamp flashing).

SENSOR
Transmission control switch

SYMPTOMS
No overdrive cancel when switch is cycled

DIAGNOSTIC TROUBLE CODES
P1780, tested during Key ON Engine OFF (KOEO) On-Board Diagnostic only

ACTUATOR
Transmission control indicator lamp

SYMPTOMS
Failed ON - overdrive cancel mode always indicated, no flashing for electronic pressure control circuit shorted. Failed OFF - overdrive cancel mode never indicated, no flashing for electronic pressure control circuit shorted, also may be due to a bad fuse. Erratic operation (flashing) may be due to a wiring concern.

DIAGNOSTIC TROUBLE CODE
P1779