MANIFOLD 6L2536 - Caterpillar

Table 2
Implement ECM (MID 82)
DTC Description System Response
168-3 Electrical System Voltage : Voltage above normal The ECM activates this diagnostic code when the system voltage is above 32.0 VDC.
168-4 Electrical System Voltage : Voltage below normal The ECM activates this diagnostic code when the system voltage is below 18.0 VDC. Diagnostic Trouble Code (DTC) Root Causes and Schematics
Possible Causes for an FMI 3 diagnostic code are:
A charging system component has failed.
The harness wiring has failed.
The ECM has failed. A failure of the ECM is unlikely.The FMI 3 error code will be logged when the system voltage is greater than 32.0 VDC. System electronics may be damaged if the voltage remains high for an extended time.Possible Causes for an FMI 4 diagnostic code are:
A charging system component has failed.
The harness wiring has failed.
The ECM fuse at the fuse panel is open.
The ECM has failed. A failure of the ECM is unlikely.The FMI 4 error code will be logged when the system voltage is less than 18.0 VDC.
Illustration 1 g03353418
Schematic of the 24V circuit for the Transmission ECM.
Illustration 2 g03353450
Schematic of the 24V circuit for the Implement ECM.
Note: The diagram above is a simplified schematic of the System Voltage connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic , RENR9783 for the complete schematic.Troubleshooting Procedure
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.
Table 3
Troubleshooting Test Steps Values Results
1. Identify Active FMI Code Associated With The Electrical Power Supply Code present FMI 3 diagnostic code, proceed to Test Step 2.
FMI 4 diagnostic code, proceed to Test Step 5.
Begin Process For DTC 168-3 Troubleshooting HERE
2. Check The System Voltage At The ECM
A. Turn key start switch and disconnect switch OFF.
B. At the harness connector for the ECM, use the 7X-1710 Multimeter Probes to measure the supply voltage.
C. Insert the probe along the positive power supply circuit wires at the contact point indicated on one of the illustrations above.
D. Insert the negative probe along the supply return circuit wires.
E. Start the engine and run the engine at high idle while monitoring the voltage.
The measured voltage is in the range of 18 VDC to 32 VDC. OK - The voltage measurement of the ECM power supply is in the range of 18 VDC to 32 VDC. The system voltage is correct. The result from this test would indicate that the alternator and machine power supply circuit is correct.
Proceed to Test Step 3.
NOT OK - The voltage measurement of the ECM power supply is greater than 32 VDC..
Repair: The alternator is not working correctly. Refer to Service Manual, SENR4130 for brushless alternators