Relay - Test
The following is a list of codes associated with the relays related to the Transmission ECM.
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| Transmission/Chassis ECM (MID 27) | ||
| DTC | Code Description | System Response |
| 144-3 | Back Up Alarm Relay : Voltage Above Normal | Back Up Alarm will not Function |
| 144-5 | Back Up Alarm Relay : Current Below Normal | Back Up Alarm will not Function |
| 144-6 | Back Up Alarm Relay : Current Above Normal | Back Up Alarm will not Function |
| 420-3 | Secondary Steering Relay : Voltage Above Normal | Secondary Steering Motor will not Function
A Warning Level 3 Will Be Generated. The automatic secondary steering test will not be able to complete at startup causing an E560 to activate. |
| 420-5 | Secondary Steering Relay : Current Below Normal | Secondary Steering Motor will not Function
A Warning Level 3 Will Be Generated. The automatic secondary steering test will not be able to complete at startup causing an E560 to activate. |
| 420-6 | Secondary Steering Relay : Current Above Normal | The automatic secondary steering test will not be able to complete at startup causing an E560 to activate. |
| 444-3 | Starter Motor Relay : Voltage Above Normal | Starter Motor will not function
A Warning Level 2 Will Be Generated. |
| 444-5 | Starter Motor Relay : Current Below Normal | Starter Motor will not function
A Warning Level 2 Will Be Generated. |
| 444-6 | Starter Motor Relay : Current Above Normal | Starter Motor will not function
A Warning Level 2 Will Be Generated. |
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| |
| Illustration 1 | g06372630 |
Possible causes for an FMI 3 Diagnostic code are:
- The relay has failed
- The energize circuit of the relay is shorted to the +battery circuit
- The ECM has failed. ECM failure is unlikely
- Possible causes for an FMI 5 Diagnostic code are:
- The energize circuit of the relay is open.
- The return circuit of the relay is open.
- The relay has failed.
- The ECM has failed. ECM failure is unlikely.
Possible causes for an FMI 6 Diagnostic code are:
- The energizer circuit of the relay is shorted to ground
- The relay has failed
- The ECM has failed. ECM failure is unlikely
Note: The diagram above is a simplified schematic of the relays and the Relay connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, M0098753 (LRC) for the complete schematic.
Diagnostic Trouble Code Procedure
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| Required Tools | |||
|---|---|---|---|
| Tool | Part Number | Description | Qty |
| T1 | 146-4080(1) | Digital Multimeter Group | 1 |
| 8T-3224 | Needle Tip Group | 1 | |
| 7X-1710 | Multimeter Probe Group | 1 | |
| 8T-8726 | Cable Assembly (Three Pin) (3-Pin Breakout) | 1 | |
| T2 | JERD2129 | Cat® Electronic Technician (Cat ET) | 1 |
| Windows-based PC | 1 | ||
| 466-6258 | Communication Adapter Gp | 1 | |
| T3 | 6V-4148 | Connector Repair Kit (Sure Seal) | 1 |
| T4 | 190-8900 | Connector Field Repair Kit (Deutsch) | 1 |
| T5 | 175-3700 | Connector Repair Kit Deutsch DT | 1 |
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| (1) | This multimeter can use an RS232C cable to connect to a Laptop computer or Dataview tool gp for troubleshooting. |
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. Check the wiring harness for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. 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 "FMI 3".
- FMI 5 diagnostic code, proceed to "FMI 5".
- FMI 6 diagnostic code, proceed to "FMI 6".
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| Check The Machine Harness For A Short | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Turn the key start switch and disconnect switch to the OFF position. 2. Disconnect the relay from the harness. 3. Disconnect the ECM machine harness connectors. 4. At the ECM machine harness connector, measure the resistance between the signal contact and all other contacts that are used in the ECM. |
Each resistance measurement is greater than 5KΩ. | Result: All resistance measurements are greater than 5K Ω. Proceed to "Check If The Diagnostic Code Remains" Table 4. Result: One or more 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 greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit. Proceed to "Check If The Diagnostic Code Remains" Table 4. |
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| Check If The Diagnostic Code Remains | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the key start switch and the disconnect switch to the ON position. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock. 6. Check if the diagnostic code is active. |
The diagnostic code is no longer present. | Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The 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 the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP. |
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| Check The Relay | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Turn the key start switch and disconnect switch to the OFF position. 2. Disconnect the relay from the wiring harness. 3. At the machine harness connector for the relay, place a jumper wire between the signal wire and the signal return. 4. Turn the key start switch and the disconnect switch to the ON position. Do not start the engine. 5. Observe the status of the diagnostic code. |
The diagnostic code changes from an FMI 5 to an FMI 6 after the jumper wire is installed. | Result: The harness is correct. The diagnostic code changes from an FMI 5 to an FMI 6 after the jumper wire is installed. The relay has failed. Repair - Replace the relay. Proceed to "Check If The Diagnostic Code Remains" 7. Result: The diagnostic code remains active. Proceed to "Check The Harness For An Open" Table 6. |
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| Check The Harness For An Open | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Turn key start switch and disconnect switch to the OFF position. 2. Disconnect the machine harness connectors from the ECM. 3. The jumper wire remains installed. 4. At the ECM machine harness connector, measure the resistance between the signal contact and the return contact. |
The resistance is less than 5 Ω. | Result: The resistance is less than 5 Ω. The machine harness is correct. Proceed to "Check If The Diagnostic Code Remains" 7. Result: The resistance is greater than 5 Ω. The resistance measurement is not correct. There is an open circuit in the machine harness. Repair: 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 "Check If The Diagnostic Code Remains" 7. |
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| Check If The Diagnostic Code Remains | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the key start switch and the disconnect switch to the ON position. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock. 6. Check if the diagnostic code is active. |
The diagnostic code is no longer present. | Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The 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 the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP. |
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| Check The Relay | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Turn the key start switch and disconnect switch to the ON position. 2. Observe the status of the diagnostic code. 3. Disconnect the relay from the machine harness. |
The FMI 6 changes to FMI 5 when the relay is disconnected. | Result: FMI 6 changes to FMI 5 when the relay is disconnected. The harness is correct. The relay has failed. Repair: Repair or replace the relay. Proceed to "Check If The Diagnostic Code Remains" Table 10. Result: The diagnostic code remains active. Proceed to "Check The Return Circuit For A Short To Ground" Table 9. |
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| Check The Return Circuit For A Short To Ground | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Turn key switch and disconnect switch to the OFF position. 2. The relay remains disconnected from the machine harness. 3. Disconnect the machine harness connectors from the ECM. 4. At the ECM machine harness connector, measure the resistance between the signal contact and all other contacts that are used in the ECM. |
Each resistance measurement is greater than 5K Ω. | Result: Each resistance measurement is greater than 5K Ω. The machine harness is correct. Proceed to "Check If The Diagnostic Code Remains" Table 10. Result: Each resistance measurement is not greater than 5K Ω. A short circuit exists between the signal circuit and the circuit with the low-resistance measurement. Repair: Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement greater than 5K Ω indicates an open in the circuit. Proceed to "Check If The Diagnostic Code Remains" Table 10. |
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| Check If The Diagnostic Code Remains | ||
|---|---|---|
| Troubleshooting Test Steps | Values | Results |
| 1. Reconnect all harness connectors. Return machine to normal operating condition. 2. Turn the key start switch and the disconnect switch to the ON position. 3. Clear all diagnostic codes. 4. Operate the machine. 5. Stop the machine and engage the safety lock. 6. Check if the diagnostic code is active. |
The diagnostic code is no longer present. | Result: The diagnostic code does not exist currently. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. Result: The 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 the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP. |
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