844K Wheel Dozer Caterpillar

Relay - Test

Usage:

844K K4Y

Transmission ECM

The following is a list of codes associated with the relays related to the Transmission ECM.

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Table 1
Transmission ECM (MID 81)
DTC	Code Description	System Response
144-3	Backup Alarm Relay: Voltage Above Normal	The backup alarm is ON.
144-6	Backup Alarm Relay: Current Above Normal	The backup alarm is OFF.
444-3	Starter Motor Relay: Voltage Above Normal	Possibility that Starter Motor is ON constantly.
444-6	Starter Motor Relay: Current Above Normal	Starter Motor will not function.
3467-3	Machine Power Relay: Voltage Above Normal	The machine electrical system is disabled.
3467-5	Machine Power Relay: Current Below Normal	The machine electrical system is disabled.
3467-6	Machine Power Relay: Current Above Normal	The machine electrical system is disabled.
3470-3	Machine Power Distribution Relay : Voltage Above Normal	The machine electrical system is disabled.
3470-5	Machine Power Distribution Relay: Current Below Normal	The machine electrical system is disabled.
3470-6	Machine Power Distribution Relay: Current Above Normal	The 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 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. This situation 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	g03651729
Transmission ECM J2 Relay connections

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, UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic" for the complete schematic. Electrical Schematic, UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic" for the complete schematic.

Diagnostic Trouble Code Procedure

Note: Prior to beginning 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.

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Table 2
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 5 diagnostic code, proceed to Test Step 3. FMI 6 diagnostic code, proceed to Test Step 6.
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 relay connected to ECM, disconnect J1 and J2 connectors from ECM. If 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 greater than 5K Ω.	OK - All resistance measurements are greater than 5K Ω. Proceed to Test Step 8. NOT OK - 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 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. STOP
Begin Process For FMI 5 Troubleshooting HERE
3. Check The Harness For An Open A. Key start switch and disconnect switch OFF. B. Disconnect the relay from the wiring harness, removing the coil resistance from the circuit. Install a jumper wire from the signal to return contacts in place of the relay. C. Disconnect J1 and J2 connectors from the ECM. D. Review the electrical schematic (above) to identify the signal and return wires for the relay. E. Use a multimeter to measure the resistance From the signal to return wire on the ECM harness.	The resistance of the harness is less than 5 Ω.	OK - The harness resistance is less than 5 Ω. Proceed to Test Step 4. NOT OK - The resistance is greater than 5K Ω. The harness is open. Repair: Replace or repair the harness. Note: After the harness is replaced, confirm the diagnostic code is no longer active. 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. STOP
4. Check The Relay A. Machine harness remains disconnected from the ECM. B. Turn key start switch and disconnect switch OFF. C. Reconnect the relay back into the harness. D. At the harness connector at the ECM, measure the resistance from the signal to return contact.	The resistance of the coil should measure around 24 Ω, unless otherwise specified on the schematic. Variation can occur due to temperature.	OK - All resistance measurements are in the acceptable range. Proceed to Test Step 5. NOT OK - The resistance measurements are not in the acceptable range. Repair: The relay has failed. Replace the relay. STOP
5. Check If The Diagnostic Code Remains A. Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage. B. Perform a 45 N (10 lb) pull test on each of the wires that is associated with the circuit. C. Reconnect all harness connectors and verify that the connectors are fully seated. Verify that any clips for connectors are fully fastened. D. Operate the machine. E. Check if diagnostic code for the relay is active.	Code for relay 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 reduce repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP
Begin Process For FMI 6 Troubleshooting HERE
6. 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 Ω.	OK - The resistance is less than 50 Ω. Proceed to Test Step 7.. NOT OK - The resistance is greater than 5K Ω. The relay has failed Repair: Replace the relay. Note: After the relay is replaced, confirm diagnostic code is no longer active. Note: A resistance that is greater than 50 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. STOP
7. 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 ECM. D. At harness connector for ECM, measure resistance between the relay contact and all ground contacts.	Each reading is greater than 5K Ω.	OK - All machine harness readings are correct. Proceed to Test Step 8. NOT OK - A short circuit exists in the machine harness. Repair: The short is between the 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 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. STOP
8. 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 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 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 reduce repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP