PM620, PM622, PM820, PM822 and PM825 Cold Planers Electronic System Sensor Signal (Analog, Active) - Test Caterpillar


Sensor Signal (Analog, Active) - Test
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1.1. Machine ECM
2.1. Transmission ECM
3.1. Steering ECM
4.1. Diagnostic Trouble Code (DTC) Procedure

Machine ECM

This type of sensor is distinguished by the presence of a voltage, ground, and signal connection to complete the sensor circuit. The output of this sensor is a voltage that falls into an expected output range. This sensor is associated with multiple electronic control modules. This sensor is used to measure fuel levels (or other fluids), or brake charge pressure (or other pressures).

The following is a list of Diagnostic Trouble Codes (DTC) associated with the active (analog) circuits of the Machine ECM.

Table 1
Machine ECM (MID 39) 
DTC  Code Description  System Response 
96-3  Fuel Level Sensor : Voltage Above Normal  The fuel level will not be displayed accurately. 
96-4  Fuel Level Sensor : Voltage Below Normal  The fuel level will not be displayed accurately. 

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. This situation 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. A failure of the ECM is unlikely.


Illustration 1g06023864
Schematic for the Analog, Active Sensors associated with the Machine ECM.

Note: The preceding diagrams are simplified schematics for the solenoids of the Machine ECM. The schematics are electrically correct. However, not all the possible harness connectors are shown.Refer to the appropriate media number below for the complete Electrical Schematic: (S/N: JCF; LH9; 8RF; EL6) Machines refer to Electrical Schematic, UENR6397. (S/N: JB9; JFC; LB8; FG4; TPH; XS6) Machines refer to Electrical Schematic, UENR6398. (S/N: JB7; HN8; HC8; RL3; H6S; 626) Machines refer to Electrical Schematic, UENR8363. (S/N: SL8; TLZ; ESE; AK5; AN8; EE2; E8S; 3C6; 627) Machines refer to Electrical Schematic, UENR8362.The schematic will illustrate locations for all the electrical components and harness connectors that are installed on the machine.

Transmission ECM

This type of sensor is distinguished by the presence of a voltage, ground, and signal connection to complete the sensor circuit. The output of this sensor is a voltage that falls into an expected output range. This sensor is associated with multiple electronic control modules. This sensor is used to measure fuel levels (or other fluids), or brake charge pressure (or other pressures).

The following is a list of diagnostic trouble codes (DTC) associated with the active (analog) circuits of the Transmission ECM.

Table 2
Transmission ECM (MID 81) 
DTC  Code Description  System Response 
4949-3  Water Spray Pressure Sensor : Voltage Above Normal  This fault may result in the spray system being inactive or the pattern of the spray system being inconsistent. 
4949-4  Water Spray Pressure Sensor : Voltage Below Normal  This fault may result in the spray system being inactive or the pattern of the spray system being inconsistent. 

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. This situation 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. A failure of the ECM is unlikely.


Illustration 2g06207124
Schematic for the Analog, Active Sensors associated with the Transmission ECM.

Note: The preceding diagrams are simplified schematics for the solenoids of the Transmission ECM. The schematics are electrically correct. However, not all the possible harness connectors are shown.Refer to the appropriate media number below for the complete Electrical Schematic: (S/N: JCF; LH9; 8RF; EL6) Machines refer to Electrical Schematic, UENR6397. (S/N: JB9; JFC; LB8; FG4; TPH; XS6) Machines refer to Electrical Schematic, UENR6398. (S/N: JB7; HN8; HC8; RL3; H6S; 626) Machines refer to Electrical Schematic, UENR8363. (S/N: SL8; TLZ; ESE; AK5; AN8; EE2; E8S; 3C6; 627) Machines refer to Electrical Schematic, UENR8362.The schematic will illustrate locations for all the electrical components and harness connectors that are installed on the machine.

Steering ECM

Table 3
Steering ECM (MID 150) 
DTC  Code Description  System Response 
4676-3  Left Grade Control Ski Position Sensor : Voltage above normal  The Steering ECM logs the diagnostic when the analog input voltage is above 4.80 V for 500 m seconds. The diagnostic deactivates but remains logged when the voltage returns to the normal operating range between 0.20 V and 4.80 V for 200 m seconds. If the voltage jumps from below 0.20 V to above 4.80 V and remains for 200 m seconds, this diagnostic will activate. 
4676-4  Left Grade Control Ski Position Sensor : Voltage below normal  The Steering ECM logs the diagnostic when the analog input voltage is below 0.20 V for 500 m seconds. The diagnostic deactivates but remains logged when the voltage returns to the normal operating range between 0.20 V and 4.80 V for 200 m seconds. If the voltage jumps from above 4.80 V to below 0.20 V and remains for 200 m seconds, this diagnostic will activate. 
4677-3  Right Grade Control Ski Position Sensor : Voltage above normal  The Steering ECM logs the diagnostic when the analog input voltage is above 4.80 V for 500 m seconds. The diagnostic deactivates but remains logged when the voltage returns to the normal operating range between 0.20 V and 4.80 V for 200 m seconds. If the voltage jumps from below 0.20 V to above 4.80 V and remains for 200 m seconds, this diagnostic will activate. 
4677-4  Right Grade Control Ski Position Sensor : Voltage below normal  The Steering ECM logs the diagnostic when the analog input voltage is below 0.20 V for 500 m seconds. The diagnostic deactivates but remains logged when the voltage returns to the normal operating range between 0.20 V and 4.80 V for 200 m seconds. If the voltage jumps from above 4.80 V to below 0.20 V and remains for 200 m seconds, this diagnostic will activate. 
5578–3  Water Tank Level Sensor : Voltage Above Normal  If the water level sensor location code is “Installed” and if the voltage reading from the sensor is above 4.8 volts for at least 0.5 seconds, a water pressure differential sensor "Voltage Above Normal" diagnostic shall become active and remain active until the voltage is below 4.8 volts. While the diagnostic is active the Water Level Percent PID shall output the appropriate DSI. Inhibit this diagnostic when the water level sensor location code shows “Not Installed”. 
5578–4  Water Tank Level Sensor : Voltage Below Normal  If the water level sensor location code is “Installed” and If the voltage reading from the water sensor is below 0.2 volts for at least 0.5 seconds, a water pressure differential sensor "Voltage Below Normal" diagnostic shall become active and remain active until the voltage is above 0.2 volts. While the diagnostic is active the Water Level Percent PID shall output the appropriate DSI. Inhibit this diagnostic when the water level sensor location code shows “Not Installed”. 

Before performing this procedure, inspect the harness connectors that are involved in the 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 this diagnostic code is active before performing this procedure.

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 for the sensor is shorted to the +battery.

  • The sensor has failed.

  • The Machine ECM has failed. A failure of the Machine ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed

  • The signal circuit for the sensor is shorted to ground

  • The Machine ECM has failed. A failure of the Machine ECM is unlikely.


Illustration 3g06207127
Steering ECM Sensor Signal (Analog, Active) Connections

Note: The preceding diagrams are simplified schematics for the Sensors (Analog, Active) of the Steering ECM. The schematics are electrically correct. However, not all the possible harness connectors are shown.Refer to the appropriate media number below for the complete Electrical Schematic: (S/N: JCF; LH9; 8RF; EL6) Machines refer to Electrical Schematic, UENR6397. (S/N: JB9; JFC; LB8; FG4; TPH; XS6) Machines refer to Electrical Schematic, UENR6398. (S/N: JB7; HN8; HC8; RL3; H6S; 626) Machines refer to Electrical Schematic, UENR8363. (S/N: SL8; TLZ; ESE; AK5; AN8; EE2; E8S; 3C6; 627) Machines refer to Electrical Schematic, UENR8362.The schematic will illustrate locations for all the electrical components and harness connectors that are installed on the machine.

Diagnostic Trouble Code (DTC) Procedure

Note: Before performing this procedure, inspect the harness connectors that are involved in the 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 this diagnostic code is active before performing this procedure.

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

A. Use Cat ®ET to confirm all logged diagnostic codes for the machine.

B. Compare the codes to the codes listed in the table above. 

Code is 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 At The Sensor

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

B. Disconnect the machine harness from the 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 ± 0.3 VDC. 
OK - The voltage reading is correct for the suspected faulty sensor.

Proceed to Test Step 3.

STOP

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

Repair: If there is an active CID 41, troubleshoot the code. If there is not an active CID 41, 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 to the OFF position.

C. At the harness connector for the sensor, place a jumper wire between the signal contact and frame ground.

D. Disconnect the J1 and J2 harness connectors from the ECM.

E. At 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 ECM connector and observe the resistance readings. Repeat the process for the sensor connector. 

The resistance is less than 5 Ωconstantly during the manipulation of the harness. 
OK - The resistance is less than 5 Ω. The signal and 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 Ω.

Repair: Check the signal circuit or the ground circuit for opens or bad connections.

Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or a corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates 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 to the OFF position.

C. Remove the jumper wire installed in the previous step.

D. Measure the resistance between the signal wire and all +battery wires used in the J1 and J2 harness connectors. 

Resistance is greater than 5K Ω for all readings. 
OK - The resistance is greater than 5K Ω. The harness circuit is correct.

Proceed to Test Step 7.

NOT OK - The resistance less than 5 Ω.

Repair: A short exists in the harness between the +battery and signal circuit. Repair or replace the machine harness.

Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or a corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates 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 the 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.

Note: To assure sensor replacement has corrected the problem, use Cat ET to check for the presence of the faulty code.

STOP

NOT OK - The FMI 4 diagnostic code remains active when sensor is disconnected. The sensor is 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 to the OFF position.

B. Disconnect the J1 and J2 harness 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 Ω. 
OK - The resistance is greater than 5K Ω. The harness circuit is correct.

Proceed to Test Step 7.

NOT OK - The resistance is less than 5 Ω. A short circuit exists between frame ground and the signal circuit.

Repair: Repair or replace the machine harness.

Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or a corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit.

STOP 
7. Check If The Diagnostic Code Remains

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

B. Clear all diagnostic codes.

C. Operate the machine.

D. Stop machine and engage the parking brake.

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 currently. 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 AVSpare. This consultation may greatly reduce repair time.

Follow the procedure in Troubleshooting, "ECM - Replace" to replace the ECM.

STOP 

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