CHECK GEARBOX indicator lamp: Notes

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 by the main instrument unit and is grounded internally by the main instrument unit. TCM sends continuous bus information CHECK GEARBOX, unit ON/OFF.

When CHECK GEARBOX is active, the control unit will ground the output for the lamp, which then comes 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.