950M and 962M Wheel Loaders Caterpillar


Sensor Signal (Analog, Active) - Test

Usage:

962M EJB


Implement ECM

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

Table 1
Implement ECM (MID 82 ) 
DTC
(1) 
Code Description  System Response 
96-3  Fuel Level Sensor: Voltage Above Normal  Fuel level indicator will not display accurately. 
96-4  Fuel Level Sensor: Voltage Below  Fuel level indicator will not display accurately. 
2203-3  Steering Valve Control Module Spool Position Signal Lines: Voltage Above Normal  The spool position is used for the steering control for all speeds. If this Diagnostic Code is active, the steering system will use the cylinders to determine if the steering is responding as expected. 
2203-4  Steering Valve Control Module Spool Position Signal Lines: Voltage Below Normal  The spool position is used for the steering control for all speeds. If this Diagnostic Code is active, the steering system will use the cylinders to determine if the steering is responding as expected. 
2903-3  Rear Wiper Control Position Sensor: Voltage Above Normal  This diagnostic code is associated with the Rear Wiper Control Position Sensor. The FMI 03 diagnostic code is recorded when the Relay Driver Module reads the signal from sensor and the voltage is above normal. This diagnostic code is activated on the Transmission ECM via CAN Data Link. The sensor is located internally to the wiper panel on a film. 
2904-3  Front Wiper Control Position Sensor: Voltage Above Normal  This diagnostic code is associated with the Front Control Position Sensor. The FMI 03 diagnostic code is recorded when the Relay Driver Module reads the signal from sensor and the voltage is above normal. This diagnostic code is activated on the Transmission ECM via the CAN Data Link. The sensor is located internally to the wiper panel on a film. 
(1) Diagnostic Codes for components that are connected to the Relay Driver Module are communicated to the Implement ECM via CAN Data Link.

Possible causes for an FMI 3 Diagnostic code are:

  • The power supply circuit for the sensor is open.

  • The return circuit is open.

  • The signal circuit is open or the sensor is disconnected.

  • The sensor probe is bent or deformed.

  • The signal circuit is shorted to the sensor power supply.

  • The sensor has failed.

  • The sensor was activated in Cat ET when the component is not on the machine.

  • The ECM has failed. An ECM failure is unlikely.

Possible causes for an FMI 4 Diagnostic code are:

  • The signal circuit for the sensor is shorted to ground.

  • The sensor probe is bent or deformed.

  • The sensor has failed.

  • The ECM has failed. An ECM failure is unlikely.


Illustration 1g03538556
Schematic of the Analog Active circuits

Note: The diagram above is a simplified schematic of the connections for the sensor signal (analog active) 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 signal (analog active) circuits of the machine.

Table 2
Transmission ECM (MID 81 ) 
DTC  Code Description  System Response 
2976-3  Parking Brake Oil Pressure Sensor: Voltage Above Normal  If this Diagnostic Code is active, the system will use the solenoid state to determine whether the Parking Brake is engaged or disengaged. If machine speed is 0 and the transmission is in Neutral, the machine will apply the Parking Brake. 
2976-4  Parking Brake Oil Pressure Sensor: Voltage Below Normal  If this Diagnostic Code is active, the system will use the solenoid state to determine whether the Parking Brake is engaged or disengaged. If machine speed is 0 and the transmission is in Neutral, the machine will apply the Parking Brake. 
2987-3  Brake Charge Pressure Sensor #1: Voltage Above Normal  This diagnostic code is associated with the Brake Charge Pressure Sensor #1. If this Diagnostic Code is active, the software will default to the Brake Charge Pressure Sensor #2. 
2987-3  Brake Charge Pressure Sensor #1: Voltage Above Normal  This diagnostic code is associated with the Brake Charge Pressure Sensor #1. If this Diagnostic Code is active, the software will default to the Brake Charge Pressure Sensor #2. 

Possible causes for an FMI 3 Diagnostic code are:

  • The power supply circuit for the sensor is open.

  • The return circuit is open.

  • The signal circuit is open or the sensor is disconnected.

  • The signal circuit is shorted to the sensor power supply.

  • The sensor has failed.

  • The sensor was activated in Cat ET when the component is not on the machine.

  • The ECM has failed. An ECM failure is unlikely.

Possible causes for an FMI 4 Diagnostic code are:

  • The signal circuit for the sensor is shorted to ground.

  • The sensor has failed.

  • The ECM has failed. An ECM failure is unlikely.


Illustration 2g03642897
Schematic of the Analog Active circuits

Note: The diagram above is a simplified schematic of the connections for the sensor signal (analog active) 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.

Table 3
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 8.0 ± 0.5 VDC or 5.0 ± 0.5 VDC 
OK - The voltage reading is correct for the suspected faulty sensor.

Proceed to Test Step 3.

NOT OK- The voltage is NOT correct for the circuit.

Repair: If there is an active CID 263 (Digital Sensor Power Supply 8 VDC Or 12 VDC) or CID 262 (5 V Sensor DC Power Supply) troubleshoot the code.
If there is not an active CID 263 or 262 replace the circuit breaker associated with the sensor.

Proceed to Test Step 7. 
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 4.

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.

Proceed to Test Step 7. 
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.

Proceed to Test Step 7. 
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.

Proceed to Test Step 7.

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 6. 
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.

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 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 

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