FUSE-25 AMP 4402537 - Caterpillar

Illustration 1 g00596481
Schematic For Speed Sensor (Engine)Note: This speed sensor is sometimes referred to as a magnetic pickup (MPU).The EMCP II monitors engine speed in order to use the information when the information is needed for other tasks. The following list contains tasks that use the information from the speed sensor:
Activating an engine overspeed shutdown
Terminating engine cranking
Determining the oil step speed
Engaging the air shut off solenoidsThe EMCP II does not control engine speed. The engine speed sensor is mounted on the flywheel housing of the engine. The sensor creates a sine wave signal from passing ring gear teeth at the rate of one pulse per tooth. The sensor sends the GSC a sine wave signal in which the frequency is in direct proportion to the speed of the engine. The GSC treats a CID 190 as a shutdown fault. The engine is not allowed to crank when this diagnostic code is active.Note: Engines that are equipped with a electronic governor have a separate speed sensor with the cable marked "973-458", "458-873", "973-407", or "873-507". The cable of the speed sensor that is used by the GSC is marked "838-873" or "838-973".Note: Faults are created when the harness connector (40 contact) is disconnected from the GSC during these troubleshooting procedures. Clear these created faults after the particular fault is corrected. In a properly operating system, when the harness connector is removed from the GSC, the following diagnostic codes are recorded:
CID 100 FMI 3 pressure sensor (engine oil)
CID 110 FMI 3 temperature sensor (engine coolant)
CID 111 FMI 3 fluid level sensor (engine coolant)
CID 190 FMI 3 speed sensor (engine)
CID 331 FMI 2 switch (engine control)
CID 336 FMI 2 switch (engine control)ProcedureThe following conditions could be the cause of a CID 190 FMI 3:
There is an open circuit of the signal.Clear the diagnostic code from the fault log after troubleshooting is complete.
Check the harness and the sensor.
Turn the ECS to OFF/RESET.
Disconnect the harness connector from the GSC.
At the GSC harness connector, measure the resistance from contact 1 to contact 2. Expected Result: The resistance should be 100 to 350 ohm. Results:
OK - The fault is most likely intermittent. Reconnect the harness connector to the GSC. Turn the ECS to OFF/RESET and then turn the ECS to STOP. Verify that a CID 190 remains active on the upper display.
If a CID 190 is showing, continue with this procedure. Proceed to next step.
If a CID 190 is NOT showing, this step has corrected the fault. STOP. If you are desired then continue with this procedure. Proceed to next step.
NOT OK - The harness wiring or the speed sensor is faulty. Proceed to 2.
Check the resistance of the sensor.
Disconnect the speed sensor from the engine harness. The speed sensor remains fastened to the engine.
At the connector of the speed sensor, measure the resistance between contact "1" and contact "2".Expected Result: The resistance should be 100 to 350 ohm. Results:
OK - The resistance of the speed sensor is correct. Proceed to next step.
NOT OK - Replace