HOUSING AS 1903391 - Caterpillar

key start switch and the battery disconnect switch must be in the OFF position.
Disconnect the speed sensor from the machine harness connector. Remove the speed sensor from the mount. Inspect the sensor tip. The tip should be clean and free of debris. Clean the tip if required.
Check the resistance of the sensor coil. The resistance should be in the range that is listed before this test step:
Use a multimeter set on DC voltage to check the operation of the sensor. With the positive meter probe on contact 2 and the negative meter probe on contact 1, move a ferrous metal object such as the tip of a metal screwdriver up to the tip of the sensor. The multimeter should show a change as the object is moved to the sensor tip and away from the sensor tip. Expected Result:The sensor tip is clean, the resistance of the sensor coil is in the acceptable range, and the operation of the speed sensor has been tested and verified to be correct.Results:
YES - The operation of the speed sensor is correct. The speed sensor does not appear to be causing the problem. Proceed to Test Step 2.
NO - The operation of the speed sensor is not correct. Either the resistance of the sensor coil is not in range or the sensor is not changing states as the metal object is passed under the tip. Repair: The speed sensor has failed. Replace the speed sensor. Install the speed sensor into the mount. Screw the speed sensor in until light contact with the flywheel is felt. Unscrew the speed sensor approximately one half of a full turn. Lock the speed sensor securely in place with the locking nut.Verify that the operation of the speed sensor is correct before returning the truck to normal operation.STOPTest Step 2. CHECK THE SPEED SENSOR CIRCUITS FOR AN OPENThe key start switch and the battery disconnect switch remain in the OFF position.The speed sensor remains disconnected from the machine harness.
At the machine harness connector for the speed sensor, connect a jumper wire between contact 1 451-BR(Brown) and contact 2 450-YL(Yellow).
At the Drivetrain ECM, disconnect the J1 harness connector. Examine the pins and sockets on the ECM and on the J1 connector. Ensure that all of the pins and sockets are secured in the connector, the contacts are clean, and the contacts are in good condition.
At the disconnected J1 connector, measure the resistance between the sensor + circuit contact J1-2 (wire 450-YL(Yellow)) and the sensor - circuit contact J1-3 (wire 450-YL(Yellow)).
While observing the resistance measurement, wiggle the machine harness connector J1 and the wiring harness. If possible, while observing the resistance measurement, have someone wiggle the connector and the harness for the speed sensor. Gently pull on the wires and move the wires around. Do not disconnect the jumper wire. Expected Result:The resistance measurement is less than 5 ohms at all times during the manipulation of the harness and the connectors.Results:
OK - The resistance measurement is less than 5