ISB/ISBe Series Engines – 019-332   Switched Road Speed Governor Limit Switch Circuit

CAUTION  To reduce the possibility of damage to the connector pins, do not use probes or leads other than Part Numbers 3164110 and 3164112. The leads must fit tightly in the connector without expanding the pins of the connector.

If INSITE™ is available, monitor the switched road speed governor limit switch circuit for proper operation. If

not, follow the troubleshooting procedures in this section.

Disconnect the OEM harness from the ECM.

Insert a test lead into pin 25 of the OEM harness connector, and attach it to a multimeter probe. Touch the other multimeter probe to the engine block ground.

Move the switched road speed governor limit switch to the ON position. The multimeter

must show a closed circuit (10 ohms or less). If the circuit is

not closed, inspect wire number 25 for an open circuit. Refer to the OEM troubleshooting and repair manual. If the resistance is within specification, wire number 25

must be checked for a short circuit to ground, a short circuit from terminal to terminal, and a short circuit to an external voltage source.

Isolate the switched road speed governor limit switch circuit.

Insert a test lead into pin 25 of the OEM harness connector, and attach it to the multimeter probe. Touch the other multimeter probe to the engine block, and 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 switched road speed governor limit switch circuit, provided that the switch has been previously checked.

Repair or replace the wire connected to pin 25 according to the vehicle manufacturer’s instructions.

Isolate the switched road speed governor limit switch circuit.

Insert one of the test leads into pin 25 of the OEM harness connector. Insert the other test lead into pin 1 of the connector. Connect the alligator clips to the multimeter probes. Measure the resistance.

The multimeter

must show an open circuit (100k ohms or more).

Remove the lead from pin 1, and check all other pins. The multimeter

must show an open circuit (100k ohms or more).

If the circuit is

not open, there is a short circuit from the wire connected to pin 25 to any pin that measured less than 100k ohms.

Repair or replace the wires in the OEM harness according to the vehicle manufacturer’s instructions.

Isolate the switched road speed governor limit switch circuit. Turn the keyswitch to the ON position. Set the multimeter to measure VDC.

Insert the test lead connected to the positive (+) multimeter probe into pin 25 of the OEM harness connector.

Disconnect the negative (-) multimeter probe from the test lead, touch it to the engine block ground, and measure the voltage. The voltage

must be 1.5 VDC or less.

NOTE: An external voltage source is any wire in the OEM harness wiring that carries the voltage.

If the voltage value is more than 1.5 VDC, there is a short circuit between the wire connected to pin 25 and a wire carrying power in the OEM harness. Repair the OEM harness according to the vehicle manufacturer’s procedures.

Connect all components after completing the repairs.