CM850 Electronic Control System – 019-438   Station Select Switch Circuit

The station select switch is a momentary switch located on the control panel and has two settings, ON and OFF (default position).

Disconnect the Smart Multiplex module connector from the Smart Multiplex module.

Touch the probe to the station select switch signal pin of the Smart Multiplex module connector. Touch the other probe to the keyswitch pin of the Smart Multiplex module connector.

Hold the switch depressed to the ON position. The multimeter must show a closed circuit (10 ohms or less). If the circuit is not closed, inspect the station select switch for an open circuit. Refer to Procedure 019-437.

If the resistance is within specification, the station select switch circuit must be checked for a short circuit to ground, and a short circuit from terminal to terminal.

Disconnect the Smart Multiplex module connector from the Smart Multiplex module.

Adjust the multimeter to measure resistance.

Touch the multimeter probe to the station select switch signal pin of the Smart Multiplex module connector. Touch the other probe to the unswitched battery (-) pin of the Smart Multiplex module connector.

Leave the slow idle switch in the OFF position.

Measure the resistance.

The multimeter must show an open circuit (100k ohms or more). If the circuit is not open, there is a short circuit to ground in the station select circuit, checked.

Repair or replace the signal wire connected to the station select switch and/or the signal wire connected to the Smart Multiplex module.

Check for a short circuit from pin to pin. Set all switches of the C-Cruise Switch control module to the OFF position. Touch the multimeter probe to the station select switch signal pin on the Smart Multiplex module connector. Touch the other probe to all of the other signal pins of the Smart Multiplex module connector in succession.

The multimeter must show and open circuit (100k ohms of more) for each pin check.

If the circuit is not open, there is a short circuit between the station select circuit and any pin that shows a closed circuit, provided the switch has previously checked.

Repair or replace the appropriate wire in the Smart Multiplex module harness or C-Cruise switch panel harness.