Home » ISX11.9 CM2250 - Service Manual » Cummins ISX11.9 CM2250 – Service Manual 019-269   Switched Maximum Operating Speed Switch Circuit

Cummins ISX11.9 CM2250 – Service Manual 019-269   Switched Maximum Operating Speed Switch Circuit

Resistance Check

TOC

 CAUTION 

The leads must fit tightly in the connector without expanding the pins in the connector otherwise the connector will be damaged.

If INSITE™ electronic service tool is available, monitor the switched maximum operating speed switch circuit for proper operation. If
not, follow the troubleshooting procedures in this section.

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Disconnect the original equipment manufacturer (OEM) harness from the electronic control module (ECM). Set the multimeter to measure resistance.

Insert a test lead into the switched maximum operating speed switch return (-) pin of the OEM harness connector, and connect the alligator clip to the multimeter probe. Touch the other lead to the switched maximum operating speed switch input pin of the connector, and connect the alligator clip to the other multimeter probe.

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Move the switched maximum operating speed switch to the ON position. The multimeter
must show 10 ohms or less (closed circuit). If the circuit is
not closed, inspect both the return (-) wire and the input wire for an open circuit, provided that the switch has been previously checked.

Refer to the OEM troubleshooting and repair manual. If the resistance is within specification, both the return (-) wire and the input wire
must be checked for a short circuit to ground, a short circuit from pin-to-pin, and a short circuit to an external voltage source.

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Check for Short Circuit to Ground

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Isolate the switched maximum operating speed switch circuit.

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Insert one of the test leads into the switched maximum operating speed switch return (-) pin of the OEM harness connector, and connect the alligator clip to the multimeter probe. Touch the other multimeter probe to the engine block, and measure the resistance.

The multimeter
must show 100k ohms or more (open circuit). If the circuit is
not open, there is a short circuit to ground in the switched maximum operating speed switch circuit, provided that the switch has been previously checked.

Repair or replace the wire connected to the return (-) pin according to the vehicle manufacturer’s instructions.

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Check for Short Circuit from Pin to Pin

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Isolate the switched maximum operating speed switch circuit. Disconnect the OEM harness connector from the ECM. Set the multimeter to measure resistance.

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Insert a test lead into the maximum operating speed switch input pin of the OEM harness connector. Insert the other test lead into the switch return pin of the connector. Connect the alligator clips to the multimeter probes.

Measure the resistance.

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

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Remove the lead from the maximum operating speed switch return pin, and check all other pins.

The multimeter
must show 100k ohms or more (open circuit) at all pins. If the circuit is
not open, there is a short circuit from the wire between the applicable pins that measured less than 100k ohms.

Repair or replace the wires in the OEM harness. Refer to Procedure
019-071.

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Check for Short Circuit to External Voltage Source

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

Set the switched maximum operating speed switch to normal. Disconnect the OEM harness connector from the ECM. Turn the vehicle keyswitch to the ON position. Set the multimeter to measure VDC.

Insert a test lead into the switched maximum operating speed switch input pin of the OEM harness connector. Connect the lead to the positive (+) multimeter probe.

Touch the negative (-) multimeter probe to the engine block ground, and measure the voltage. The voltage
must be 1.5 VDC or less.

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If the voltage value is more than 1.5 VDC, there is a short circuit between the wire connected to the switched maximum operating speed switch input pin and a wire carrying power in the OEM harness. Repair the OEM harness. Refer to Procedure
019-071.

Connect all components after completing the repairs.

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Last Modified:  30-May-2008