374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Supply

Sensor Supply - Test

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit [UENR2724]

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Signal (Analog, Passive) - Test

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Solenoid Return - Test

ELECTRICAL AND STARTING SYSTEM

SENSOR GP

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Signal (Analog, Passive) - Test

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Supply - Test

374F and 390F Excavators and 390F MHPU Mobile Hydraulic Power Unit Sensor Signal (PWM) - Test

1.1. Machine ECM

2.1. Implement ECM 1

3.1. Implement ECM 2

4.1. Diagnostic Trouble Code Procedure

Machine ECM

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

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Table 1
Machine ECM (MID 299)
DTC	Code Description	System Response
41 -6	8 Volt DC Supply: Current Above Normal	Multiple failures of systems or components associated with this code.
3041 -6	12 Volt Sensor Power Supply: Current Above Normal	Multiple failures of systems or components associated with this code.

The diagnostic code is recorded when the interface module indicates that the current of the sensor supply circuit is too high.

Possible causes of an FMI 06 Diagnostic code are:

The sensor supply output is shorted to ground.
A sensor in the power supply circuit has failed.
The Machine ECM may have failed. This situation is unlikely.

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Illustration 1	g06108754
Schematic of the Sensor Supply circuits

Note: The diagram above is a simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) for the complete schematic.

Implement ECM 1

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Table 2
Implement ECM 1 (MID 432)
DTC	Code Description	System Response
41-3	8 Volt DC Supply: Voltage Above Normal	Sensors powered by the 8V supply will not function properly.
41-4	8 Volt DC Supply: Voltage Below Normal	Sensors powered by the 8V 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 03 Diagnostic code are:

The output of the sensor supply has shorted to the + battery circuit.
The Implement ECM has failed. The ECM failing is unlikely.

Possible causes of an FMI 04 Diagnostic code are:

The output of sensor supply has an open circuit.
A sensor has failed.
The ECM has failed. This situation is unlikely.

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Illustration 2	g03464424
Schematic of the Sensor Supply circuits

Note: The diagram above is a simplified schematic of the Implement ECM 1 connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) for the complete schematic.

Implement ECM 2

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Table 3
Implement ECM 2 (MID 433)
DTC	Code Description	System Response
41-3	8 Volt DC Supply: Voltage Above Normal	Sensors powered by the 8V supply will not function properly.
41-4	8 Volt DC Supply: Voltage Below Normal	Sensors powered by the 8V 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 03 Diagnostic code are:

The output of the sensor supply has shorted to the + battery circuit.
The Implement ECM has failed. The ECM failing is unlikely.

Possible causes of an FMI 04 Diagnostic code are:

The output of sensor supply has an open circuit.
A sensor has failed.
The ECM has failed. This situation is unlikely.

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Illustration 3	g03464425
Schematic of the Sensor Supply circuits

Note: The diagram above is a simplified schematic of the Implement ECM 2 connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR2487 (374F) or Electrical Schematic, UENR2489 (390F) 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.

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Table 4
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. FMI 6 diagnostic code, proceed to Test Step 5.
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 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 7. 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 Ω	OK - Each resistance measurement is less than 5 Ω. The ground circuit is correct. Proceed to test step 4. NOT OK -One or more of the resistance measurements is greater than 5 Ω. 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. Repair the machine harness or replace the machine harness. Proceed to Test Step 7.
Begin Process For FMI 4 Troubleshooting HERE
4. Check The Supply Circuits A. The disconnect switch remains in the ON position and the Key Switch in the RUN position. The machine harness connector remains disconnected from the ECM. B. Measure the resistance between the Key Switch RUN contact and each of the battery (+) contacts that are connected to the machine harness connector J1.	The resistance is less than 5K Ω,	OK - Each resistance measurement is less than 5 Ω. 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 Ω. 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. Proceed to Test Step 7.
Begin Process For FMI 6 Troubleshooting HERE
5. Check For A Short To Ground 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 frame ground and the contact for the supply of the sensor.	The resistance is greater than 5K Ω	OK - The harness circuit resistance is correct. Verify that the diagnostic code is present. Repair: Perform this procedure again. Also, recheck if the diagnostic code is active. Proceed to Test Step 7. NOT OK - The resistance is less than 5 Ω. The machine harness or a sensor has failed. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. Proceed to Test Step 6.
6. Disconnect Each Sensor And Check For A Short To Ground. A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the sensors from the machine harness one at a time. C. After a sensor is disconnected, check the resistance from frame ground to sensor supply of the machine harness connector for the ECM. Repeat for each sensor.	The resistance is greater than 5K Ω,	OK - The resistance is greater than 5K Ω. The harness circuit resistance is correct. The sensor that was last disconnected has failed. Repair: Replace the sensor that caused the short. Proceed to Test Step 7. NOT OK - Resistance is less than 5 Ω after all the sensors have been disconnected from the machine harness. The machine harness is shorted to ground. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. Repair: Repair or replace the machine harness. Proceed to Test Step 7.
7. 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 Communicator at your dealership for possible consultation with AVSpare. This consultation may effect repair time. Refer to Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.