CUP-SPECIAL TAPERED 1649921 - Caterpillar

Note: The diagram above is a simplified schematic of the Implement ECM 3 connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2694 for the complete schematic.
Diagnostic Trouble Code 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. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.
Table 5
Troubleshooting Test Steps    Values    Results    
1. Identify The Active FMI Code Associated With The Sensor Supply Circuit     Code present     FMI 3 diagnostic code, proceed to Test Step 3.
FMI 4 diagnostic code, proceed to Test Step 4.
FMI 6 diagnostic code, proceed to Test Step 5.    
2. Check The Voltage At The ECM
A. Turn the key start switch and the battery disconnect switch to the OFF position.
B. At the machine harness connector for the ECM, insert a 7X-1710 Multimeter Probe along the contact for the sensor power. Insert another probe along the return contact for the sensor power.
C. Turn the disconnect switch to the ON position.
E. Observe the voltage measurement for the multimeter and wiggle the machine harness connectors of the ECM. Gently pull on the wires and move the wires around.    
See the schematic to determine the voltage that is applicable to each circuit.     OK - The voltage is appropriate for the circuit as determined by the schematic. Proceed to Test Step 3.
NOT OK - The voltage measurement is unstable. The voltage measurement is showing a large amount of variation. The manipulation of the machine harness and connectors does not affect the measurement. Proceed to Test Step 5.
NOT OK - The voltage measurement is stable and within the specified range. However, the measurement between the ECM + battery contact and the ECM (-) battery contacts are not stable or in the correct range at all times. Proceed to test step 3.    
Begin Process For FMI 3 Troubleshooting HERE    
3. Check The Ground Circuits
A. Turn the key start switch and the disconnect switch OFF.
B. Disconnect the machine harness from the ECM.
C. At the ECM harness connector, measure the resistance between each of the return wires and frame ground.    
The resistance is less than 5 Ω     OK - Each resistance measurement is less than 5 ohms. The ground circuit is correct. Proceed to test step 4.
NOT OK - One or more of the resistance measurements is greater than 5 ohms. There is an open circuit or a poor connection in the ground circuit.
Repair: The open or a possible poor connection is in the ECM ground circuit in the