Relay - Test
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the relay circuits of the machine.
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| Power Train ECM (MID 081) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 144-3 | Backup Alarm Relay: Voltage Above Normal | Back Up Alarm will not function |
| 144-6 | Backup Alarm Relay: Current Above Normal | Back Up Alarm will not function |
| 444-3 | Starter Motor Relay: Voltage Above Normal | Starter Motor will not function. |
| 444-5 | Starter Motor Relay: Current Below Normal | Starter Motor will not function. |
| 444-6 | Starter Motor Relay: Current Above Normal | Starter Motor will not function. |
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 indicator lamp has failed
- The ECM has failed. ECM failure is unlikely
Possible causes for an FMI 5 Diagnostic code are:
- The relay has failed
- There is an open in the circuit
- 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
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| |
| Illustration 1 | g06160136 |
|
Schematic of the Relay circuits | |
Note: The diagram above is a simplified schematic of the connections for the relay circuits. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic for the complete schematic.
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the relay circuits of the machine.
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| Machine ECM (MID 039) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 3467-3 | Main Power Relay: Voltage Above Normal | Machine electrical system is disabled. |
| 3467-5 | Main Power Relay: Current Below Normal | Machine electrical system is disabled. |
| 3467-6 | Main Power Relay: Current Above Normal | Machine electrical system is disabled. |
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 indicator lamp has failed
- The ECM has failed. ECM failure is unlikely
Possible causes for an FMI 5 Diagnostic code are:
- The relay has failed
- There is an open in the circuit
- 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
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| |
| Illustration 2 | g06336170 |
|
Schematic of the Relay circuits | |
Note: The diagram above is a simplified schematic of the connections for the relay circuits. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic 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. For sensors powered via the fuse / breaker panel, check the condition of the appropriate fuse / breaker before beginning the troubleshooting procedure.
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Identify Active FMI Code Associated With Relay Circuit | Code present. |
FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 5. FMI 5 diagnostic code, proceed to Test Step 3. FMI 6 diagnostic code, proceed to Test Step 5. |
| Begin Process For FMI 3 Troubleshooting HERE | ||
| 2. Check The Machine Harness For A Short A. Turn key start switch and disconnect switch OFF. B. Disconnect harness connection at relay. C. If the relay connected to ECM, disconnect J1 and J2 connectors from ECM. If the relay connected to Switch Panel, disconnect all Switch Panel connectors. D. Measure resistance of relay signal contact to all J1 and J2 connectors, if relay is wired directly to Transmission ECM. If relay is wired directly to switch panel, measure resistance of relay contact to all switch panel connectors. |
Each reading is greater than 5K ohms. |
OK - All resistance measurements are greater than 5K ohms. Proceed to Test Step 7. NOT OK - One or more readings are less than 5 ohms. 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 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP |
| Begin Process For FMI 5 Troubleshooting HERE | ||
| 3. Check The Relay A. Turn the key start switch and the disconnect switch OFF. B. Remove the relay. C. Place a jumper wire between the signal contact and the return contact of the relay. D. Turn the key start switch and the disconnect switch ON. Do not start the engine. E. As the jumper is removed and connected to the contacts, observe any code change. |
The code changes to FMI 6 after the jumper wire is installed. |
OK - The circuit is correct. The relay has failed. Repair: Replace the relay. After replacement of the relay, confirm that the diagnostic code is not active. Proceed to Test Step 7. NOT OK - The diagnostic code remains active. Proceed to Test Step 4. |
| 4. Check The Machine Harness For An Open A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the harness connectors from the ECM. C. The jumper wire remains installed. D. At the machine harness connector for the ECM, measure the resistance at the ECM contacts for the relay. |
Each reading is less than 5 ohms . |
OK - The reading is less than 5 ohms, the harness is correct. Proceed to Test Step 7. NOT OK - The reading is greater than 5K ohms . Circuit open in machine harness. Repair: The open is in the wire for the relay signal or the return wire for the relay. Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. Proceed to Test Step 7. |
| Begin Process For FMI 4 & FMI 6 Troubleshooting HERE | ||
| 5. Check The Indicator Lamp A. Key start switch and disconnect switch OFF. B. Disconnect the relay from the wiring harness. C. Review the electrical schematic (above) to identify the input and output wires from the coil of the relay. D. Use a multimeter to measure the resistance across the coil of the relay. |
The resistance of the coil is less than 50 ohms. |
OK - The resistance is less than 50 ohms . Proceed to Test Step 6. NOT OK - The resistance is greater than 5K ohms. The relay has failed Repair: Replace the relay. Note: After the relay is replaced, confirm that diagnostic code is no longer active. Note: A resistance that is greater than 50 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. Proceed to Test Step 7. |
| 6. Check Machine Harness For A Short To Ground A. Machine harness remains disconnected from relay. B. Turn key start switch and disconnect switch OFF. C. Disconnect harness connectors from the ECM (or switch panel). D. At harness connector for ECM, measure resistance between lamp relay contact and all ground contacts. |
Each reading greater than 5K ohms. |
OK - All machine harness readings are correct. Proceed to Test Step 7. NOT OK - A short circuit exists in the machine harness. Repair: The short is between the lamp contact for the relay and the circuit with the low resistance. Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. Proceed to Test Step 7. |
| 7. Check If The Diagnostic Code Remains A. Turn key switch and disconnect switch ON. B. Clear all diagnostic codes. C. Operate the machine. D. Stop machine and engage the parking brake. E. Check if diagnostic code for the relay is active. |
Code for relay 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 (or Switch Panel) may require replacement. Repair: Prior to replacing this component, contact the Technical Communication (TC) at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP |
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