CHECK GEARBOX indicator lamp

Fig 1: Identifying Communication Diagram - CHECK GEARBOX Indicator Lamp

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Communication Circuit Diagram - CHECK GEARBOX Indicator Lamp

Courtesy of SAAB-SCANIA OF AMERICA, INC.

If there is a fault in the automatic transmission or its control module, the TCM lights the CHECK GEARBOX warning lamp in the main instrument unit.

The lamp is powered from the main instrument unit and is grounded by the main instrument unit control module. TCM sends continuous bus information CHECK GEARBOX, unit ON/OFF.

With CHECK GEARBOX on, the control module grounds the output for the lamp to turn it on.

The lamp will go out when TCM sends the message CHECK GEARBOX OFF.

When the ignition is turned on, the TCM lights the lamp for approx. 3 seconds and if there is no fault the lamp will go out.