CYLINDER AS 9T8943 - Caterpillar

Illustration 1 g03810627
Schematic of the Engine Speed Sensor
This diagnostic code is associated with the Engine Speed Sensor. The FMI 02 means that the ECM has determined that the data is erratic, intermittent, or incorrect. The engine speed sensor has a signal wire and a ground. The ECM is able to diagnose the signal wire. The signal wire provides a frequency input to the ECM that is proportional to engine speed. The ECM will continue to report an active diagnostic code until a good sensor signal is observed by the ECM. The engine must be running in order for the ECM to determine if the active code can be cleared. The possible causes of this diagnostic code are listed below:
The sensor has failed.
Intermittent connections or poor connections.
Mechanical devices are loose.
The ECM has failed. The ECM failing is unlikely.Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 190 FMI 02 is active before performing this procedure.Test Step 1. Check For A Short On The Signal Circuits
Disconnect the negative battery cable and turn the key start switch to the OFF position.
Disconnect the machine harness J1 connectors from the machine ECM.
Check the continuity between the contact for the signal wire J1-37 (A481-YL(Yellow)) and all pins on the J1 connector.
Check the continuity between the contact for the return wire J1-30 (P770-WH(White)) and all pins on the J1 connector. Expected Result:The measurements for resistance are greater than 5000 ohms.Results:
OK - The measurements for resistance are greater than 5000 ohms. Proceed to Test Step 3.
NOT OK - The resistance on one or more circuits is less than 5000 ohms. There is a short in the circuit with the low resistance measurement.Repair: The machine harness has failed. Repair the machine harness or replace the machine harness. After the repair, start the engine. Check if the diagnostic code is cleared.STOPTest Step 2. Check The Signal Circuit For An Open In The Machine Harness
Place a jumper between contact 2 (481-YL(Yellow) and the return wire 1 (P770-WH(White) of the machine harness connector for the speed sensor.
Disconnect connectors J1 from the machine harness of the ECM.
Measure the resistance from the contact for the signal wire J1-37 (481-YL(Yellow)) and J1-30 (P770-WH(White)) connector. Expected Result:The resistance that is measured is less than 5 ohms.Results:
OK - The resistance that is measured is less than 5 ohms. The signal circuit in the machine harness is correct.STOP
NOT OK - The CID 190 FMI 02 is active. The diagnostic code has not been corrected. The speed sensor may have failed.Repair: If the cause of the problem is not found, contact the