950M and 962M Wheel Loaders Caterpillar


Sensor Signal (Analog, Passive) - Test

Usage:

962M EJB


Implement ECM

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

Table 1
Implement ECM (MID 82) 
DTC  Code Description  System Response 
600-3  Hydraulic Oil Temperature Sensor: Voltage above normal  Hydraulic oil temperature will be unavailable. Calibrations and service tests cannot be initiated.
This code is triggered when the system voltage is greater than 4.9 VDC. 
600-4  Hydraulic Oil Temperature Sensor: Voltage below normal  Hydraulic oil temperature will be unavailable. Calibrations and service tests cannot be initiated.
This code is triggered when the system voltage is less than 0.2 VDC. 

Possible causes for an FMI 3 Diagnostic code are:

  • The return circuit is open.

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

  • The signal circuit is shorted to another circuit.

  • 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 for the sensor is shorted to ground.

  • The sensor has failed.

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


Illustration 1g03545519
Schematic of the Analog Passive circuits

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

Table 2
Transmission ECM (MID 81) 
DTC  Code Description  System Response 
177-3  Transmission Oil Temperature Sensor: Voltage above normal  This failure may cause the transmission oil temperature to be incorrect. This will affect the quality of the shift. 
177-4  Transmission Oil Temperature Sensor: Voltage below normal  This failure may cause the transmission oil temperature to be incorrect. This will affect the quality of the shift. 
427-3  Front Axle Temperature Sensor: Voltage above normal  When the Front Axle Temperature Sensor is Faulted, it will not be considered in determining whether to activate the High Front Axle Oil Temperature Event E2129. 
427-4  Front Axle Temperature Sensor: Voltage below normal  When the Front Axle Temperature Sensor is Faulted, it will not be considered in determining whether to activate the High Front Axle Oil Temperature Event E2129. 
428-3  Rear Axle Temperature Sensor: Voltage above normal  When the Rear Axle Temperature Sensor is Faulted, it will not be considered in determining whether to activate the High Rear Axle Oil Temperature Event E2130. 
428-4  Rear Axle Temperature Sensor: Voltage below normal  When the Rear Axle Temperature Sensor is Faulted, it will not be considered in determining whether to activate the High Rear Axle Oil Temperature Event E2130 
826-3  Flushing Oil Temperature/Torque Converter Oil Temperature Sensor: Voltage above normal  This failure may cause the oil temperature to be incorrect. This will affect the quality of the shift. 
826-4  Flushing Oil Temperature/Torque Converter Oil Temperature Sensor: Voltage below normal  This failure may cause the oil temperature to be incorrect. This will affect the quality of the shift. 

Possible causes for an FMI 3 Diagnostic code are:

  • The return circuit is open.

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

  • The signal circuit is shorted to another circuit.

  • 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 for the sensor is shorted to ground.

  • The sensor has failed.

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

Table 3
Temperature  Sensor Output Resistance (Ohms) 
-25 °C (-13 °F)  13052.6 
-20 °C (-4 °F)  9716.7 
-15 °C (5 °F)  7302.3 
-10 °C (14 °F)  5538.0 
-5 °C (23 °F)  4236.7 
0 °C (32 °F)  3268.3 
5 °C (41 °F)  2541.5 
10 °C (50 °F)  1991.4 
15 °C (59 °F)  1571.9 
20 °C (68 °F)  1249.5 
25 °C (77 °F)  1000.0 
30 °C (86 °F)  805.5 
35 °C (95 °F)  652.8 
40 °C (104 °F)  532.3 


Illustration 2g03545525
Schematic of the Analog Passive circuits

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

Table 4
Troubleshooting Test Steps  Values  Results 
1. Identify The Active DTC Code Associated With The Suspect 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 Sensor

Note: See Table 3 for a list of resistances related to specific temperature values. The maximum resistance for the sensor is 33,650 Ω, the minimum is 51.2 Ω.

A. Turn the key start switch and the disconnect switch to the OFF position.

B. Disconnect the sensor from the harness.

C. Measure the resistance between pin 1 and 2 of the sensor. 

The resistance reading agrees with the values from Table 3. 
OK - The resistance reading agrees with the values in 3.

Proceed to Test Step 3.

NOT OK - The resistance reading does not agree with the values in 3.

Repair: Replace the sensor.

STOP 
3. Check For An Open In The Sensor Circuit

A. The key start switch and disconnect switch remain in the OFF position.

B. The harness connector remains disconnected from the sensor.

C. Disconnect the J1 and J2 connectors from the ECM.

D. At the harness connector for the sensor install a jumper wire.

E. At the harness connector for the ECM measure the resistance at the contacts for the sensor. 

The resistance reading is less than 5 Ω. 
OK - The resistance is less than 5 Ω.

Proceed to Test Step 4.

NOT OK - The resistance is greater than 5 Ω.

Repair: Either the signal or the return circuit wire is open. Repair or replace the harness.

STOP 
4. Check The Signal Circuit For A Short.

A. The disconnect switch and the key start switch remain in the OFF position.

B. The harness connectors J1 and J2 remain disconnected from the ECM.

C. Remove the jumper wire that was installed during the previous test step..

D. At the ECM harness connectors measure the resistance between the positive connector and all J1 and J2 contacts. 

Each resistance reading is greater than 5000 Ω. 
OK - Each measurement is greater than 5000 Ω.

Proceed to Test Step 7.

NOT OK - A resistance measurement is less than 5000 Ω.

Repair: A short exists between the signal circuit and the circuit with the low resistance measurement. Repair or replace the machine harness. 
Begin Process For FMI 4 Troubleshooting HERE 
5. Check The Sensor

A. Turn key start switch and disconnect switch ON.

B. Ensure that the diagnostic code is active.

C. Disconnect sensor from machine harness.
 

DTC is active. 
OK - Diagnostic code remains active.

Proceed to Test Step 6.

NOT OK - Diagnostic code is no longer active.

Repair: Replace the sensor.

After sensor replacement, confirm code is not active.

STOP 
6. Check The Wiring Harness Of The Sensor For A Short To Ground

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

B. Disconnect machine harness connection at sensor.

C. Disconnect machine harness connections at switch panel.

D. At the machine harness connector for the switch panel, measure resistance from the signal contact of machine harness to all possible sources of ground. Measure resistance to all contacts of machine harness connectors for the monitor. 

Each reading greater than 5K Ω. 
OK - All resistance readings are greater than 5K Ω.

Proceed to Test Step 7.

NOT OK - One or more of the readings are less than 5 Ω.

Repair: A short exists between the signal contact and the circuit with the low resistance. Repair or replace the machine harness.

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.

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 

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