910K and 914K Compact Wheel Loaders Electrohydraulic System Caterpillar

Sensor Signal (Analog, Active) - Test

Usage:

910K AY4

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the analog active Sensors of the machine.

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Table 1
Machine ECM (MID 71)
DTC	Code Description	System Response
3561-3	Drive Circuit Forward Pressure Sensor: Voltage above normal	The hystat pump will be derated resulting in lower machine rimpull.
3561-4	Drive Circuit Forward Pressure Sensor: Voltage below normal	The hystat pump will be derated resulting in lower machine rimpull.
3562-3	Drive Circuit Reverse Pressure Sensor: Voltage above normal	The hystat pump will be derated resulting in lower machine rimpull.
3562-4	Drive Circuit Reverse Pressure Sensor: Voltage below normal	The hystat pump will be derated resulting in lower machine rimpull.

Possible causes for an FMI 3 diagnostic code are:

The signal circuit is shorted to another voltage circuit.
A sensor circuit is open or has a poor connection.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 4 diagnostic code are:

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

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Illustration 1	g03650642
Schematic of the Analog Active Sensors

Note: The diagram above is a simplified schematic of the Machine ECM and the Analog Active connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR4017 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 2
Troubleshooting Test Steps	Values	Results
1. Identify Active DTC Code Associated With Sensor Circuit	Code present	FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 6.
Begin Process For FMI 3 Troubleshooting HERE
2. Check The Supply Voltage at the Sensor A. Turn key start switch and disconnect switch ON. B. Disconnect the machine harness from sensor. C. Refer to the schematic to determine the voltage source for the suspected faulty sensor. D. Measure voltage between supply and return contacts at the machine harness connector for the sensor.	Voltage is 5.0 ± 0.5 VDC	OK - The voltage reading is correct for the suspected faulty sensor. Proceed to Test Step 4. STOP NOT OK- The voltage is NOT correct for the circuit. Repair - Replace the circuit breaker associated with the sensor.
3. Check For An Open In The Sensor Circuit A. The sensor remains disconnected from the machine harness. B. Turn the key start switch and the disconnect switch OFF. C. At the harness connector for the sensor, place a jumper wire between the signal contact and frame ground. D. Disconnect J1 and J2 harness connectors from the ECM. E. At the machine harness connector for the ECM, measure the resistance from the signal contact for the sensor to frame ground. F. Gently pull on the wire and move the wire in a circular motion at the ECM connector and observe the resistance readings. Repeat the process for the sensor connector.	The resistance is less than 5 ohms at all times during the manipulation of the harness.	OK - The resistance is less than 5 ohms. The signal circuit and the ground circuits of the sensor are not open in the machine harness. Proceed to Test Step 5. NOT OK - Resistance reading for the signal circuit or the return circuit is greater than 5 ohms. Repair: Check the signal circuit or the ground circuit for opens or bad connections. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP
4. Check Signal Circuit For A Short To +Battery A. The Sensor and the ECM are disconnected from the harness. B. Turn the disconnect switch and the key start switch OFF. Remove the jumper wire installed in the previous step. C. Measure the resistance between the signal wire and all other wires used in the J1 and J2 harness connectors.	Resistance greater than 5K ohms for all readings.	OK - The resistance is greater than 5K ohms. The harness circuit is correct.. Proceed to Test Step 7. NOT OK- The resistance less than 5 ohms. Repair: A short exists in the harness between the +battery and signal circuit. Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP
Begin Process For FMI 4 Troubleshooting HERE
5. Check The Sensor A. With FMI 4 active, disconnect the sensor from the machine harness. B. Observe Cat ET or the operator monitor for code change as the sensor is disconnected and connected to harness.	Code changes from FMI 4 to FMI 3.	OK - The diagnostic changed to FMI 3 when the sensor was disconnected. Repair: Replace the sensor. STOP NOT OK - The FMI 4 diagnostic code remains active when sensor is disconnected. The sensor not the cause of the problem. Proceed to Test Step 7.
6. Check The Signal Circuit For A Short To Ground A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the J1 and J2harness connectors from the ECM. C. Measure the resistance between the signal contact for sensor and all other contacts used in the J1 and J2 harness connectors.	The resistance is greater than 5K ohms.	OK - The resistance is greater than 5K ohms. The harness circuit is correct. Proceed to Test Step 7. NOT OK - The resistance is less than 5 ohms. A short circuit exists between frame ground and the signal circuit. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP
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 safety lock lever. E. Check if the diagnostic code for the sensor is active.	The code for the sensor is NO longer present.	OK - The diagnostic code 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 connections. Resume machine operation. STOP NOT OK - The diagnostic trouble code has not been corrected. Repair: Recheck the circuit and perform this procedure again. If the diagnostic code is still active, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Follow the procedure in Troubleshooting, "ECM - Replace" to replace the ECM. STOP