Sensor Supply - Test
The following is a list of Diagnostic Trouble Codes (DTCs) associated with the sensor power supply circuits of the machine.
Show/hide table
| Brake ECM (MID 116) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 41-3 | 8 VDC Supply : Voltage above normal | Sensors powered by the 8 VDC supply may not function properly. |
| 41-4 | 8 VDC Supply : Voltage below normal | Sensors powered by the 8 VDC supply may not function properly. |
| 1482-3 | 10 VDC Sensor DC Power Supply : Voltage above normal | Sensors powered by the 10 VDC supply may not function properly. |
| 1482-4 | 10 VDC Sensor DC Power Supply : Voltage below normal | Sensors powered by the 10 VDC supply may not function properly. |
Possible causes for an FMI 3 Diagnostic code are:
- The sensor supply or the ground circuit in the machine harness is open.
- The signal circuit in the machine harness is shorted to another circuit.
- The signal circuit in the machine harness is open or the sensor is disconnected.
- 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 in the machine harness is shorted to ground.
- The sensor has failed.
- The ECM has failed. An ECM failure is unlikely.
Show/hide table
| |
| Illustration 1 | g06019174 |
|
Schematic of the Sensor Supply | |
The preceding diagram is a simplified schematic of the Brake ECM and the Sensor Supply connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to Electrical Schematic, UENR4664, "785G Off-Highway Truck Electrical System" for the complete schematic.
The following is a list of Diagnostic Trouble Codes (DTCs) associated with the sensor power supply circuits of the machine.
Show/hide table
| Chassis ECM (MID 87) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 41-3 | 8 VDC Supply : Voltage above normal | Sensors powered by the 8 VDC supply may not function properly. |
| 41-4 | 8 VDC Supply : Voltage below normal | Sensors powered by the 8 VDC supply may not function properly. |
| 262-3 | 5 VDC Sensor DC Power Supply : Voltage above normal | Sensors powered by the 5 VDC supply may not function properly. |
| 262-4 | 5 VDC Sensor DC Power Supply : Voltage below normal | Sensors powered by the 5 VDC supply may not function properly. |
| 1482-3 | 10 VDC Sensor DC Power Supply : Voltage above normal | Sensors powered by the 10 VDC supply may not function properly. |
| 1482-4 | 10 VDC Sensor DC Power Supply : Voltage below normal | Sensors powered by the 10 VDC supply may not function properly. |
Possible causes for an FMI 3 Diagnostic code are:
- The sensor supply or the ground circuit in the machine harness is open.
- The signal circuit in the machine harness is shorted to another circuit.
- The signal circuit in the machine harness is open or the sensor is disconnected.
- 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 in the machine harness is shorted to ground.
- The sensor has failed.
- The ECM has failed. An ECM failure is unlikely.
Show/hide table
| |
| Illustration 2 | g03675912 |
|
Schematic of the Sensor Supply | |
The preceding diagram is a simplified schematic of the Chassis ECM and the Sensor Supply connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to Electrical Schematic, UENR4664, "785G Off-Highway Truck Electrical System" for the complete schematic.
The following is a list of Diagnostic Trouble Codes (DTCs) associated with the sensor power supply circuits of the machine.
Show/hide table
| Transmission ECM (MID 81) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 41-3 | 8 VDC Supply: Voltage above normal | Sensors powered by the 8 VDC supply may not function properly. |
| 41-4 | 8 VDC Supply: Voltage below normal | Sensors powered by the 8 VDC supply may not function properly. |
Possible causes for an FMI 3 Diagnostic code are:
- The sensor supply or the ground circuit in the machine harness is open.
- The signal circuit in the machine harness is shorted to another circuit.
- The signal circuit in the machine harness is open or the sensor is disconnected.
- 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 in the machine harness is shorted to ground.
- The sensor has failed.
- The ECM has failed. An ECM failure is unlikely.
Show/hide table
| |
| Illustration 3 | g03675915 |
|
Schematic of the Sensor Supply | |
The preceding diagram is a simplified schematic of the Transmission ECM and the Sensor Supply connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to Electrical Schematic, UENR4664, "785G Off-Highway Truck Electrical System" for the complete schematic.
Diagnostic Trouble Code Procedure
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.
- Identify the active FMI code associated with the components.
- Determine which code is present and use the list below to determine which procedure to follow.
- FMI 3 diagnostic code, proceed to Table 4.
- FMI 4 diagnostic code, proceed to Table 5.
Show/hide table
| FMI 3 Troubleshooting | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Check The Supply Voltage A. Turn the key start switch and the disconnect switch to the OFF position. B. At the harness connector, insert the positive multimeter probe along the supply positive contact. Insert the negative multimeter probe along the supply return contact. C. Turn the key start switch and the disconnect switch to the ON position. D. Observe the voltage measurement. |
The voltage measurement is in the range of 8.0 ± 0.5 VDC. |
OK - The voltage measurement is in the range of 8.0 ± 0.5 VDC. Proceed to Test Step 4. NOT OK - The voltage measurement is greater than 8.0 ± 0.5 VDC. The power supply voltage is above normal. Proceed to Test Step 2. |
| 2. Check The ECM Power Supply At The ECM With The Circuit Disconnected A. Turn the key start switch and the disconnect switch to the OFF position. B. At the ECM harness connector, remove the power supply positive circuit from the connector body. C. Turn the key start switch and the disconnect switch to the ON position. D. At the connector, measure the supply voltage with the circuits disconnected. Insert the multimeter probes at the positive contact and at the return contact. E. Measure the voltage. |
The voltage measurement is in the range of 8.0 ± 0.5 VDC. |
OK - The voltage measurement is in the range of 8.0 ± 0.5 VDC. The voltage is correct. Proceed to Test Step 4. NOT OK -The voltage measurement is greater than 8.0 ± 0.5 VDC. The power supply voltage is above normal. Proceed to Test Step 3. |
| 3. Check For A Short A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the harness connector from the sensor and ECM. C. At the harness connector for the ECM, measure the resistance between the power supply positive contact and each of the individual circuit contacts on the harness connector. |
The resistance is greater than 4K Ω. |
OK - The resistance is greater than 4K Ω. Proceed to Test Step 4. NOT OK - One or more of the resistance measurements is less than 4K Ω. There is a short circuit between a power supply circuit and another circuit in the machine harness. Repair: Repair or replace the machine harness. Proceed to Test Step 4. |
| 4. Check If The Diagnostic Code Remains A. Inspect the harness connectors and clean the contacts of the harness connectors. B. Reconnect all harness connectors. C. Turn the key switch and disconnect switch to the ON position. D. Operate the machine. E. Check if diagnostic code is active. |
Diagnostic code is no longer present. |
OK - Diagnostic code does not exist currently. Initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP NOT OK - Diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing this component, always contact the Technical Communication at your dealership for possible consultation with Caterpillar. This consultation may greatly effect repair time. Follow the steps in Troubleshooting, "Electronic Control Module (ECM) - Replace" if the ECM needs to be replaced. STOP |
Show/hide table
| FMI 4 Troubleshooting | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Check The Supply Voltage A. Turn the key start switch and the disconnect switch to the OFF position. B. At the harness connector, insert the positive multimeter probe along the supply positive contact. Insert the negative multimeter probe along the supply return contact. C. Turn the key start switch and the disconnect switch to the ON position. D. Observe the voltage measurement. |
The voltage measurement is in the range of 8.0 ± 0.5 VDC. |
OK - The voltage measurement is in the range of 8.0 ± 0.5 VDC. The voltage is correct. Proceed to Test Step 5. NOT OK - The voltage measurement is less than 8.0 ± 0.5 VDC. The power supply voltage is below normal. Proceed to Test Step 2. |
| 2. Check The Power Supply At The ECM With The Circuit Disconnected A. Turn the key start switch and the disconnect switch to the OFF position. B. At the ECM harness connector, remove the power supply positive circuit from the connector body. C. Turn the key start switch and the disconnect switch to the ON position. D. At the connector, measure the supply voltage with the circuits disconnected. Insert the multimeter probes at the positive contact and at the return contact. E. Measure the voltage. |
The voltage measurement is in the range of 8.0 ± 0.5 VDC. |
OK - The voltage measurement is in the range of 8.0 ± 0.5 VDC. The voltage is correct. Proceed to Test Step 5. NOT OK - The voltage measurement is less than 8.0 ± 0.5 VDC. The power supply voltage is below normal. Proceed to Test Step 3. |
| 3. Disconnect The Sensor A. Turn the key start switch and the disconnect switch to the ON position. B. Disconnect the machine harness from the sensor. C. Check the status of the active diagnostic code. |
The diagnostic code is no longer active. |
OK - The diagnostic code is no longer active when the sensor is disconnected. The sensor has failed. Repair: Replace the sensor. Proceed to Test Step 5. NOT OK - The problem appears to be in the cab harness. Proceed to Test Step 4. |
| 4. Check For A Short A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the harness connector from the sensor and ECM. C. At the harness connector for the ECM, measure the resistance between the power supply positive circuit contact and each individual circuit contact used on the harness connector. |
The resistance is greater than 4K Ω. |
OK - The resistance is greater than 4K Ω. Proceed to Test Step 5. NOT OK - One or more of the resistance measurements is less than 4K Ω. There is a short circuit between a power supply circuit and another circuit in the machine harness. Repair: Repair or replace the machine harness. Proceed to Test Step 5. |
| 5. Check If The Diagnostic Code Remains A. Inspect the harness connectors and clean the contacts of the harness connectors. B. Reconnect all harness connectors. C. Turn the key start switch and disconnect switch to the ON position. D. Operate the machine. E. Check if diagnostic code is active. |
Diagnostic code is no longer present. |
OK - Diagnostic code does not exist currently. Initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP NOT OK - Diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, the ECM may require replacement. Prior to replacing this component, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly effect repair time. Follow the steps in Troubleshooting, "Electronic Control Module (ECM) - Replace" if the ECM needs to be replaced. STOP |
Caterpillar Information System:
C4.4 Engines for Caterpillar Built Machines Fuel Injection Pump Gear - Remove
C1.5 and C2.2 Engines for Caterpillar Built Machines Engine Wiring Information
C15 and C18 Engines for Caterpillar Built Machines Turbocharger Oil Lines
2014/07/25 New STIC Lockout Control Limit Switch Now Used on Certain R1600G, R1600H, and R1700G Load Haul Dump Machines {1435, 3034, 4343}
2014/07/25 New STIC Lockout Control Limit Switch Now Used on Certain R1300G Load Haul Dump Machines {1435, 3034, 4343}
2014/05/30 An Improved Torque Converter Lines Group and Power Train Oil Lines Group are Now Used On Certain 789D and 793D Off-Highway Trucks {3016, 3101, 3154}
824K Wheel Dozer, 825K Soil Compactor and 826K Landfill Compactor Machine Systems Parking Brake Actuator - Adjust
794 AC Off-Highway Truck Systems Steering Control Valve
725C Articulated Truck Power Train Differential and Bevel Gear (Center) - Remove and Install
794 AC Off-Highway Truck Systems Steering Metering Pump
824K Wheel Dozer, 825K Soil Compactor and 826K Landfill Compactor Machine Systems Brake Accumulator - Test and Charge
2014/07/17 New Coolant Tubes Are Now Used for Certain 793F and 795F Off-Highway Trucks {1380}
D8T Track-Type Tractor Towing the Machine
824K Wheel Dozer, 825K Soil Compactor and 826K Landfill Compactor Machine Systems Limit Switch (Stop Light) - Adjust
424B Backhoe Loader Machine Systems Hoe Bucket - Remove and Install
785G Off-Highway Truck Specifications
785G Off-Highway Truck Declaration of Conformity
785G Off-Highway Truck Alternate Exit
824K Wheel Dozer, 825K Soil Compactor and 826K Landfill Compactor Machine Systems Limit Switch (Throttle Lock Deactivation) (Electronic Technician) - Adjust
785G Off-Highway Truck Operator Controls
826K Landfill Compactor, 825K Soil Compactor and 824K Wheel Dozer Power Train Torque Converter - Assemble
725C Articulated Truck Pressure Sensor (NRS Differential) - Remove and Install
794 AC Off-Highway Truck Systems Lubrication System
725C Articulated Truck Power Train Differential and Bevel Gear (Center) - Disassemble