PISTON 8J5979 - Caterpillar

Illustration 1 g03344640
Alternator R-Terminal CircuitThis diagnostic code is associated with the R-terminal connector of the alternator. The FMI 08 means that the ECM has determined that the signal from the terminal is abnormal. This code is active when the signal frequency of the engine speed sensor is less than 127 Hz or greater than 2000 Hz.Note: (MAT, GNZ, BPA, B5D, TFZ, B6K machines) The LH Operator ECM is located under the LH Operator Platform.Note: (MAN, GNN, TFM machines) The Operator ECM is located inside the station console attached to the service door. The possible causes of this diagnostic code are listed below:
The alternator has failed.
Intermittent connections or poor connections
Mechanical devices are loose.
The ECM has failed. ECM failure is unlikely.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 1251 FMI 08 is active before performing this procedure.Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure. System Response:When this diagnostic code is active, the following occurs:
Operator station fault lamp is active.Test Step 1. CHECK THE SIGNAL CIRCUIT FOR AN OPEN
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the alternator.
At the harness connector for the alternator, install a jumper wire from wire (403-GN).
Disconnect the J1 and J2 machine harness connectors from the ECM.
At the machine harness connector J2, measure the resistance from contact J2-14 wire (403-GN) to wire ( 403-GN) at the harness connector for the alternator.Expected Result:The resistance should be less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The machine harness is correct. Proceed to test step 2.
NOT OK - The resistance that is measured is greater than 5000 ohms. Repair: There is an open in the machine harness. Repair the machine harness or replace the machine harness. Verify that the problem has been corrected.STOPTest Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT
The key start switch and the disconnect switch remain in the OFF position.
The machine harness remains disconnected from the alternator.
Remove the jumper wire from the previous test step.
At the machine harness connectors J1 and J2, measure the resistance from contacts J2-14 (wire 403-GN) to all other J1 and J2 contacts.Expected Result:The resistance should be greater than 5 ohms for each measurement.Results:
YES - The machine harness is correct. Proceed to test step 3.
NO - The resistance is not correct.Repair: There is a short in the machine harness. The short is between the circuit with the low resistance measurement and wire (403-GN). Repair the harness or replace the harness.STOPTest Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS
Clean all contacts of the harness connector.
Reconnect all harness connectors.
Turn the disconnect switch and the key start switch to the ON position.
Clear all inactive diagnostic codes.
Operate the machine.
Check the status of the diagnostic code.Expected Result:The diagnostic code is NO longer active.Results:
YES - The diagnostic code is NO longer active. The diagnostic code