924K, 926M, 930K, 930M, 938K and 938M Wheel Loaders Caterpillar

Sensor Supply - Test

Usage:

930K FRK

Machine ECM

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

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Table 1
Machine ECM (MID 39)
DTC	Code Description	System Response
41 -3	8 VDC Supply: Voltage Above Normal	Sensors powered by the 8V supply will not function properly.
41-4	8 VDC Supply: Voltage Below Normal	Sensors powered by the 8V supply will not function properly.
262-3	5 VDC Sensor Power Supply: Voltage Above Normal	Sensors powered by the 5V supply will not function properly.
262-4	5 VDC Sensor Power Supply: Voltage Below Normal	Sensors powered by the 5V supply will not function properly.
1482-3	10 VDC Sensor Power Supply: Voltage Above Normal	Sensors powered by the 10V supply will not function properly.
1482-4	10 VDC Sensor Power Supply: Voltage Below Normal	Sensors powered by the 10V supply will not function properly.

Possible causes for an FMI 3 diagnostic code are:

The sensor supply or the ground circuit in the machine harness is open.
The signal circuit in the machine harness is shorted to another circuit.
The signal circuit in the machine harness is open or the sensor is disconnected.
The sensor has failed.
The ECM has failed. An ECM failure is unlikely.

Possible causes for an FMI 4 diagnostic code are:

The signal circuit in the machine harness is shorted to ground.
The sensor has failed.
The ECM has failed. An ECM failure is unlikely.

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Illustration 1	g03751998
Schematic of the sensor power supplies

Note: The diagram above is a simplified schematic of the connections for the sensor power supply connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the electrical schematic for the specific machine being serviced for the complete schematic.

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Table 2
Supply Voltage	Expected Voltage
5 V Supply	5.0 ± 0.25 VDC.
8 V Supply	8.0 ± 0.5 VDC.
10 V Supply	10.0 ± 1.0 VDC.

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. Check the wiring for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing a troubleshooting procedure.

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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 5.
Begin Process For FMI 3 Troubleshooting HERE
2. Check The Supply Voltage A. Turn the key start switch and the disconnect switch OFF. B. At the harness connector, insert the positive multimeter probe along the supply positive contact. Insert the negative multimeter probe along the supply return contact. C. Turn the key start switch and the disconnect switch ON. D. Observe the voltage measurement.	Refer to table 2 for the correct voltage.	OK - The expected voltage measurement is in the correct range. Proceed to Test Step 9. NOT OK - The expected voltage measurement is greater than the range. The power supply voltage is above normal. Proceed to Test Step 3.
3. Check The ECM Power Supply At The ECM With The Circuit Disconnected A. Turn the key start switch and the disconnect switch OFF. B. At the ECM harness connector, remove the power supply positive circuit from the connector body. C. Turn the key start switch and the disconnect switch ON. D. At the connector, measure the supply voltage with the circuits disconnected. Insert the multimeter probes at the positive contact and at the return contact. E. Measure the voltage.	Refer to table 2 for the correct voltage.	OK - The expected voltage measurement is in the correct range. Proceed to Test Step 4. NOT OK - The expected voltage measurement is greater than the range. The power supply voltage is above normal. Proceed to Test Step 9.
4. Check For A Short A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the harness connector from the sensor and ECM. C. At the harness connector for the ECM, measure the resistance between the power supply positive circuit at contact and each of the other individual circuit contacts that are used on the harness connector.	The resistance is greater than 4k Ω.	OK - The resistance is greater than 4k Ω. Proceed to Test Step 9. NOT OK - One or more of the resistance measurements is less than 4kΩ. There is a short circuit between a power supply circuit and another circuit in the machine harness. Repair: Repair or replace the machine harness. Proceed to Test Step 9.
Begin Process For FMI 4 Troubleshooting HERE
5. Check The Supply Voltage A. Turn the key start switch and the disconnect switch OFF. B. At the harness connector, insert the positive multimeter probe along the supply positive contact. Insert the negative multimeter probe along the supply return contact. C. Turn the key start switch and the disconnect switch ON. D. Observe the voltage measurement.	Refer to table 2 for the correct voltage.	OK - The expected voltage measurement is in the correct range. Proceed to Test Step 9. NOT OK - The expected voltage measurement is greater than the range. The power supply voltage is below normal. Proceed to Test Step 6.
6. Check The ECM Power Supply At The ECM With The Circuit Disconnected A. Turn the key start switch and the disconnect switch OFF. B. At the ECM harness connector, remove the power supply positive circuit from the connector body. C. Turn the key start switch and the disconnect switch ON. D. At the connector, measure the supply voltage with the circuits disconnected. Insert the multimeter probes at the positive contact and at the return contact. E. Measure the voltage.	Refer to table 2 for the correct voltage.	OK - The expected voltage measurement is in the correct range. Proceed to Test Step 7. NOT OK - The expected voltage measurement is greater than the range. The power supply voltage is above normal. Proceed to Test Step 9.
7. Disconnect The Position Sensor A. Turn the key start switch and the disconnect switch ON. B. Disconnect the machine harness from the sensor. C. Check the status of the active diagnostic code.	The diagnostic code is no longer active.	OK - The diagnostic code is no longer active when the sensor is disconnected. The sensor has failed. Repair: Replace the sensor.. Proceed to Test Step 9. NOT OK - The problem appears to be in the cab harness. Proceed to Test Step 8.
8. Check For A Short A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the harness connector from the sensor and ECM. C. At the harness connector for the ECM, measure the resistance between the power supply positive circuit at contact and each of the other individual circuit contacts that are used on the harness connector.	The resistance is greater than 4k Ω.	OK - The resistance is greater than 4k Ω. Proceed to Test Step 9. NOT OK - One or more of the resistance measurements is less than 4kΩ. There is a short circuit between a power supply circuit and another circuit in the machine harness. Repair: Repair or replace the machine harness. Proceed to Test Step 9.
9. Check If The Diagnostic Code Remains A. Inspect the harness connectors and clean the contacts of the harness connectors. B. Reconnect all harness connectors. C. Turn key switch and disconnect switch ON. D. Operate the machine. E. Check if diagnostic code is active.	Diagnostic code is no longer present.	OK - Diagnostic code does not exist at this time. Initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP NOT OK - Diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing this component, always contact the Technical Communication at your dealership for possible consultation with Caterpillar. This consultation may greatly effect repair time. Follow the steps in Troubleshooting, "Electronic Control Module (ECM) - Replace" if the ECM needs to be replaced. STOP