CM2150 Electronic Control System – 019-107   Intermediate Speed Control Switch

The intermediate speed control (ISC) ON, OFF, and ON switch circuit signals the ECM that the operator is requesting to go to one of two preset speeds between low idle and high idle. There is one three-position switch that selects ISC 1, OFF, and ISC 2.

The ISC circuit is shown for ISC 1 and ISC 2 features. The calibration can have only one ISC active feature. The ISC circuit is wired with a double pole, double throw (DPDT), three-position switch.

The DPDT three-position switch functions to selectively ground wires No. 23 and 33, or wires No. 25 and 33, or ground no wires. The logic of the switch is shown.

The lines that connect the switch terminals at the three lever positions are lines of continuity between the terminals.

In position 1, switch terminals No. 2, 3 and 5, 6 are connected which shorts ISC 2 and ISC validation (pins 25 and 33) to ground.

In position 2, no pins are grounded.

In position 3, switch terminals No. 1, 2 and 4, 5 are connected which shorts ISC 1 and ISC validation (pins 23 and 33) to ground.

If INSITE™ electronic service tool is available, monitor the ISC switch for proper operation. If not, follow the troubleshooting procedures in this section.

Remove the four connectors from the switch. Label the wires with the switch location and the wire numbers.

With the switch in position 1, measure the resistance from switch terminal 2 to switch terminal 3. The resistance must be 10 ohms or less.

Measure the resistance from switch terminal 5 to switch terminal 6. The resistance must be 10 ohms or less.

Measure the resistance from switch terminal 1 to all switch terminals. The resistance must be 100K ohms or more.

Measure the resistance from switch terminal 4 to all other terminals. The resistance must be 100K ohms or more.

Move the switch lever to position 2.

Measure the resistance from switch terminal 1 to all other terminals. The resistance must be 100K ohms or more.

Measure the resistance from switch terminal 2 to all other terminals. The resistance must be 100K ohms or more.

Move the switch lever to position 3.

Measure the resistance from switch terminal 1 to terminal 2. The resistance must be 10 ohms or less.

Measure the resistance from switch terminal 4 to terminal 5. The resistance must be 10 ohms or less.

Measure the resistance from switch terminal 3 to all other terminals. The resistance must be 100K ohms or more.

Measure the resistance from switch terminal 6 to all other terminals. The resistance must be 100K ohms or more.

If the multimeter does not show the correct values, the switch has failed. Verify the switch type and terminal location numbers. Refer to the OEM troubleshooting and repair manual for replacement and to verify the switch type and terminal location.