950M and 962M Wheel Loaders Caterpillar


Sensor Supply - Test

Usage:

962M EJB


Implement ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the sensor supply circuits of the machine.

Table 1
Implement ECM (MID 82) 
DTC  Description  System Response 
41-3  8 VDC Supply: Voltage Above Normal  Sensors powered by the 8 VDC supply will not function properly.
This code is triggered when the supply voltage is greater than 8.4 VDC. 
41-4  8 VDC Supply: Voltage Below Normal  Sensors powered by the 8 VDC supply will not function properly.
This code is triggered when the supply voltage is less than 7.6 VDC. 
262-3  5 VDC Supply: Voltage Above Normal  Sensors powered by the 5 VDC supply will not function properly.
This code is triggered when the supply voltage is greater than 5.4 VDC. 
262-4  5 VDC Supply: Voltage Below Normal  Sensors powered by the 5 VDC supply will not function properly.
This code is triggered when the supply voltage is less than 4.6 VDC. 
1482-3  10 VDC Supply: Voltage Above Normal  Sensors powered by the 10 VDC supply will not function properly.
This code is triggered when the supply voltage is greater than 11 VDC. 
1482-4  10 VDC Supply: Voltage Below Normal  Sensors powered by the 10 VDC supply will not function properly.
This code is triggered when the supply voltage is less than 9 VDC. 

The diagnostic code is recorded when the interface module indicates that the voltage of the sensor supply circuit is too high, too low, or erratic.

Possible causes of an FMI 3 Diagnostic code are:

  • The output of the sensor supply has shorted to the +battery circuit.

  • The ECM has failed. A failure of the ECM is unlikely.

Possible causes of an FMI 4 Diagnostic code are:

  • The output of sensor supply has an open circuit.

  • A sensor has failed.

  • The ECM has failed. A failure of the ECM is unlikely.


Illustration 1g03626919
Schematic of the Sensor Supply circuits

Note: The diagram above is a simplified schematic of the connections for the sensory supply circuits. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic, UENR3117 for the complete schematic.

Transmission ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the sensor supply circuits of the machine.

Table 2
Transmission ECM (MID 81) 
DTC  Description  System Response 
41-3  8 VDC Supply: Voltage Above Normal  Sensors powered by the 8 VDC supply will not function properly. 
41-4  8 VDC Supply: Voltage Below Normal  Sensors powered by the 8 VDC supply will not function properly. 
262-3  5 VDC Supply: Voltage Above Normal  Sensors powered by the 5 VDC supply will not function properly. 
262-4  5 VDC Supply: Voltage Below Normal  Sensors powered by the 5 VDC supply will not function properly. 
1482-3  10 VDC Supply: Voltage Above Normal  Sensors powered by the 10 VDC supply will not function properly. 
1482-4  10 VDC Supply: Voltage Below Normal  Sensors powered by the 10 VDC supply will not function properly. 

The diagnostic code is recorded when the interface module indicates that the voltage of the sensor supply circuit is too high, too low, or erratic.

Possible causes of an FMI 3 Diagnostic code are:

  • The output of the sensor supply has shorted to the +battery circuit.

  • The ECM has failed. A failure of the ECM is unlikely.

Possible causes of an FMI 4 Diagnostic code are:

  • The output of sensor supply has an open circuit.

  • A sensor has failed.

  • The ECM has failed. A failure of the ECM is unlikely.


Illustration 2g03626939
Schematic of the Sensor Supply circuits

Note: The diagram above is a simplified schematic of the connections for the sensory supply circuits. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic, UENR3117 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.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code, listed in the table above, is active before performing this procedure.

Table 3
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 2.

FMI 4 diagnostic code, proceed to Test Step 4. 
Begin Process For FMI 3 Troubleshooting HERE 
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 Transmission 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. 
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 ohms. 
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 machine harness. Refer to the complete Electrical System Schematic for a complete view of the machine harness. Ensure that the ground connections are clean, the ground connections are tight, and the ground connections are in good condition. Check all of the connectors and splice points that are in the ground circuit. Repair the machine harness or replace the machine harness. 
Begin Process For FMI 4 Troubleshooting HERE 
4. Check The Supply Circuits

Note:The disconnect switch remains in the ON position and the key start switch in the RUN position. The machine harness connector remains disconnected from the ECM.

A. Measure the resistance between the key start switch ON contact and each of the battery (+) contacts that are connected to the machine harness connector J1. 

The resistance is less than 5K ohms, 
OK - Each resistance measurement is less than 5 ohms. The supply circuit is correct. Reconnect the machine harness connector J1 to the ECM before proceeding to the next test step.

Proceed to Test Step 5.

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 supply circuit.

Repair: The open or a possible poor connection is in the system voltage supply circuit of the machine harness of the ECM. Verify that there are no open circuit breakers or fuses in the circuit.

Refer to the complete Electrical System Schematic for this machine. Check all of the connectors and splice points that are in the supply circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness. 
5. Check If The Diagnostic Code Remains

A. Turn the key start switch and the disconnect switch ON.

B. Clear all diagnostic codes.

C. Operate the machine.

D. Stop the machine and engage the parking brake.

E. Check if diagnostic code is active. 

Code for supply voltage is NO longer present. 
OK - No active diagnostic code. The problem does not exist at this time. The initial diagnostic code may have been caused by a poor electrical connection or a short at one of the harness connectors tested.

Resume normal machine operation.

NOT OK - Perform this procedure again. Verify that the measurements for the alternator are correct. Verify that the system voltage circuit connections are in good condition and verify that the system voltage circuit connections are tight.

If the problem remains and no cause can be found, the ECM may have failed. A failed ECM is unlikely. Prior to replacing the ECM, always contact the Technical Communication at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time.

Refer to Troubleshooting, "ECM - Replace" if the ECM needs to be replaced.

STOP 

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