ROD 4922447 - Caterpillar

Illustration 7 g01919073
Terminal locations at the speed/timing sensor
(Terminal 1) +8 V sensor supply
(Terminal 2) Engine speed/timing signal Test Step 1. Perform a Visual Inspection of the Installation of the Speed/Timing Sensor and Connector
Remove the electrical power from the ECM.
Illustration 8 g02641563
Speed/timing sensor (typical right front engine view)
(3) Hold-down bracket
(4) Sensor mounting flange
Visually inspect the installation of the sensor. Do not remove the sensor from the front housing.
Visually inspect the condition of the sensor and connector. Check that the components are not cracked or broken.
Check that the mounting bolt is tight and that hold-down bracket (4) is not bent or deformed.
Ensure that the sensor mounting flange (3) is flush against the housing. Check that the sensor is not loose in the housing bore.
Remove the harness connector from the sensor and visually inspect the connection at the sensor.
Check the inside of the harness connector for debris, moisture, and/or corrosion.
Perform a 45 N (10 lb) pull test on each of the wires at the harness connector.
Check the sensor connector seal for damage. Ensure that the harness connector securely locks onto the sensor.
Visually inspect the harness around the sensor connector for damage. Ensure that the harness has not been damaged by rubbing on rotating components. Expected Result:The inspection confirmed that the installation of the sensor and the condition of the harness and connector are OK.Results:
OK - The sensor is installed correctly and the harness connector is in good repair. Proceed to Test Step 2.
Not OK - A problem has been found with the installation of the sensor and/or harness or the harness connector.Repair: Perform the necessary repairs. Correct any adverse conditions that have been identified by the inspection. Replace any damaged components. Ensure that the wire tie (5) at the sensor is securely in place.Attempt to start the engine. If the repair eliminates the original problem, return the engine into service. If the problem persists, continue to the next Test Step.STOPTest Step 2. Use a Multimeter to Check the Condition of the Harness
Ensure that the electrical power has been removed from the engine. Ensure that the harness connector is disconnected at the sensor.
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Restore the electrical power to the ECM.
Illustration 9 g01993813
Test lead connections at the multimeter for the current measurement at the harness connector (typical multimeter)
Connect the test leads to the connections on the multimeter that are for measuring milliamperes ("mAµA"). Install the other end of the leads between socket terminals 1 and 2 on the harness side of the sensor connector. Place the multimeter on the "mA" scale.
Monitor the active diagnostic code and the logged diagnostic codes on Cat ET. Check for an active 678-4 ECU 8 Volts DC Supply : Voltage Below Normal.For a signal wire that is in good repair, a 678-4 diagnostic code will not be active while the multimeter is installed in the circuit.
Use the multimeter to measure the DC amperage of the circuit. Note: If the signal wire is shorted to engine ground, an attempt to measure the amperage in