Operator Control Switch (Switch to Ground) - Test
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the operator control switch of the machine.
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| Transmission ECM (MID 81) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 70-2 | Parking Brake Switch: Data erratic, intermittent, or incorrect | Parking brake will not disengage when requested. |
| 621-3 | Downshift Switch: Voltage above normal | When this diagnostic code occurs, the transmission gear will be unable to be decreased. |
| 621-4 | Downshift Switch: Voltage below normal | When this diagnostic code occurs, the transmission gear will be unable to be decreased. |
| 622-3 | Upshift Switch: Voltage above normal | When this diagnostic code occurs, the transmission gear will be unable to be decreased. |
| 622-4 | Upshift Switch: Voltage below normal | When this diagnostic code occurs, the transmission gear will be unable to be decreased. |
| 623-3 | Directional Switch: Voltage above normal | The transmission will lock in neutral until a valid neutral switch position is sensed. |
| 623-4 | Directional Switch: Voltage below normal | The transmission will lock in neutral until a valid neutral switch position is sensed.. |
| 626-3 | Steering/Transmission Lock Switch: Voltage above normal | When this diagnostic code occurs, there is no change in the system operation. The transmission will remain operational, even if the mechanical steering lock is in the locked position. |
| 626-4 | Steering/Transmission Lock Switch: Voltage below normal | When this diagnostic code occurs, there is no change in the system operation. The transmission will remain operational, even if the mechanical steering lock is in the locked position. |
Possible causes for an FMI 2 diagnostic code are:
- A short circuit exists.
- An open circuit exists.
- The switch has failed.
- The ECM has failed. A failure of the Transmission ECM is unlikely.
Possible causes for an FMI 3 diagnostic code are:
- The ground wire is open.
- A signal is permanently open.
- The switch has failed.
- The ECM has failed. A failure of the Transmission ECM is unlikely.
Possible causes for an FMI 4 diagnostic code are:
- A short to ground.
- The switch has failed.
- The ECM has failed. A failure of the Transmission ECM is unlikely.
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| |
| Illustration 1 | g03524562 |
|
Schematic of the Operator Control Switches | |
Note: The diagram above is a simplified schematic of the Transmission ECM and the Operator Control Switch connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision for the complete schematic.
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the operator control switch of the machine.
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| Implement ECM (MID 82) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 490-3 | Implement Lockout Switch: Voltage above normal | All implement functions are disabled. |
| 490-4 | Implement Lockout Switch: Voltage below normal | All implement functions are disabled. |
| 2659-2 | Cab Air Temperature Control Switch: Data erratic, intermittent, or incorrect | Air conditioning is disabled.
The Auto Temperature Control feature will not work properly |
Possible causes for an FMI 2 diagnostic code are:
- A short circuit exists.
- An open circuit exists.
- The switch has failed.
- The ECM has failed. A failure of the ECM is unlikely.
Possible causes for an FMI 3 diagnostic code are:
- The ground wire is open.
- A wire is shorted to another circuit
- The switch has failed.
- The ECM has failed. A failure of the ECM is unlikely.
Possible causes for an FMI 4 diagnostic code are:
- A wire is shorted to ground
- The switch has failed.
- The ECM has failed. A failure of the Implement ECM is unlikely.
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| |
| Illustration 2 | g03524581 |
|
Schematic of the Operator Control Switches | |
Note: The diagram above is a simplified schematic of the Implement ECM and the Operator Control Switch connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision 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.
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Identify The Active FMI Code Associated With The Sensor Circuit | Code present. |
FMI 2 diagnostic code, proceed to Test Step 2. FMI 3 diagnostic code, proceed to Test Step 4. FMI 4 diagnostic code, proceed to Test Step 9. |
| Begin Process For FMI 2 Troubleshooting HERE | ||
| 2. Check The Circuit For A Short A. Turn the key switch OFF. B. Disconnect the switch from the machine harness. C. Disconnect the J1 and J2 machine harness connections from the ECM. C. At the machine harness connector for the ECM, measure the resistance between each of the signal contacts to every other contact used in the J1 and J2 machine harness connectors. |
The resistance is greater than 5K Ω. |
OK - The resistance is correct. Proceed to Test Step 3. NOT OK - The resistance check is not correct. Repair: There is a short in the signal circuits of the machine harness. Repair or replace the machine harness. Proceed to Test Step 12. |
| 3. Check the Operation of the Switch. A. The key switch remains OFF. B. Reconnect all harness connectors. C. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation. |
The switch operates correctly. |
OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed Repair: Replace the switch. Proceed to Test Step 12. |
| Begin Process For FMI 3 Troubleshooting HERE | ||
| 4. Check the Harness For an Open A. Turn key start switch and disconnect switch OFF. B. Disconnect the switch from the machine harness. C. Disconnect the J1 and J2 machine harness connectors at the ECM. D. At the machine harness connector for the switch, place a jumper between the two signal wires at the switch connector. Check for low resistance at the ECM connector E. At the machine harness connect for the ECM, measure the resistance between the signal contact and frame ground. |
The resistance is less than 5 KΩ. |
OK - The circuit is correct. Proceed to Test Step 5. NOT OK - The resistance is greater than 5K Ω. The circuit is open. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω indicates a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω indicates an open in the circuit. Proceed to Test Step 12. |
| 5. Check the Harness for a Short A. The key switch remains OFF. B. All harness connectors remain disconnected. C. Remove the jumper wire installed in the previous step. D. At the machine harness connector for the ECM, measure resistance between the signal contacts and all other contacts of the J1 and J2 harness connectors. |
The resistances are greater than 5K Ω. |
OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 6. NOT OK- The resistance less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the wire with the low resistance reading. 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. Proceed to Test Step 12. |
| 6. Check the Ground Source for the Switch. A. The key switch remains OFF. B. All harness connectors remain disconnected. C. At the switch, measure resistance between the ground contact and frame ground. |
The resistance is less than 5 Ω. |
OK - The resistance is less than 5 Ω. Proceed to Test Step 7. NOT OK - The resistance is greater than 5K Ω. Repair: The switch does not have a good ground source. Replace the harness between the switch and the ground source. Note: A resistance that is greater than 5 Ω but less than 5K Ω indicates a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω indicates an open in the circuit. Proceed to Test Step 12. |
| 7. Check the Operation of the ECM. A. The key switch remains OFF. B. Reconnect all harness connections. C. Using a wire removal tool, remove the signal wires and socket from the machine harness connector to the switch. D. Turn the key switch ON. E. Use a multimeter probe to contact both signal wire pins through the empty space in the harness connector. F. Ground the other end of the multimeter probe to frame ground. G. Observe the status of the diagnostic code. |
The FMI 3 changes to an FMI 4. |
OK - The ECM is operating correctly. Proceed to Test Step 8. NOT OK - The FMI 3 remains active. The ECM may have failed. 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. If the ECM requires replacement, see Troubleshooting, "ECM - Replace" Proceed to Test Step 12. |
| 8. Check the Operation of the Switch. A. Turn the key switch OFF. B. Reinstall the signal wire removed in the previous step. C. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation. |
The switch operates correctly. |
OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed Repair: Replace the switch. Proceed to Test Step 12. |
| Begin Process For FMI 4 Troubleshooting HERE | ||
| 9. Check The Switch A. Turn the key switch OFF. B. Unplug the switch from the machine harness. C. Turn the key switch ON. D. Observe the status of the diagnostic code. |
The FMI 4 diagnostic code remains active. |
OK - The FMI 4 diagnostic code remains active. Proceed to Test Step 10. NOT OK - The FMI 4 changes to an FMI 3. The switch has failed. Repair: Replace the switch. Verity that the new switch corrects the diagnostic code. Proceed to Test Step 12. |
| 10. Check the Harness for a Short A. The key switch remains OFF. B. Unplug the J1 and J2 machine harness connectors form the ECM. D. At the machine harness connector for the ECM, measure resistance between the signal contact and all other contacts of the J1 and J2 harness connectors. |
The resistances are greater than 5K Ω. |
OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 11. NOT OK- The resistance less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the wire with the low resistance reading. 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. Proceed to Test Step 12. |
| 11. Check the Operation of the Switch. A. The key switch remains OFF. B. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation. |
The switch operates correctly. |
OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed. Repair: Replace the switch. Proceed to Test Step 12. |
| 12. 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 key switch and disconnect switch ON. D. Operate the machine. E. Check if diagnostic code is active. |
Diagnostic code is no longer present. |
OK - Diagnostic code does not exist at this time. 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 |
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