621K OEM Wheel Tractor-Scraper Relay

Relay - Test

621K OEM Wheel Tractor-Scraper [UENR5941]

621K OEM Wheel Tractor-Scraper Operator Control Switch (Switch to Ground) - Test

621K OEM Wheel Tractor-Scraper Sensor Signal (Analog, Active) - Test

ELECTRICAL AND STARTING SYSTEM

SWITCH GP

621K OEM Wheel Tractor-Scraper Condition Switch (Two Wire) - Test

621K OEM Wheel Tractor-Scraper Operator Control Switch (Switch to Ground) - Test

621K OEM Wheel Tractor-Scraper Relay - Test

621K OEM Wheel Tractor-Scraper Switch Circuits - Test

1.1. Transmission/Chassis ECM

2.1. Implement ECM

3.1. Possible Causes and Schematics

4.1. Diagnostic Trouble Code Procedure

Transmission/Chassis ECM

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

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Table 1
Transmission/Chassis ECM (MID 27)
DTC	Code Description	System Response
144-3	Backup Alarm Relay : Voltage Above Normal	The backup alarm is ON.
144-5	Backup Alarm Relay : Current Below Normal	The backup alarm is OFF.
144-6	Backup Alarm Relay : Current Above Normal	The backup alarm is ON.
420-3	Secondary Steer Relay : Voltage Above Normal	The relay is likely constantly active.
420-5	Secondary Steer Relay : Current Below Normal	The relay will likely not be active when requested.
420-6	Secondary Steer Relay : Current Above Normal	The relay is likely constantly active.
444-3	Starter Motor Relay : Voltage Above Normal	Starter Motor cannot be engaged.
444-5	Starter Motor Relay : Current Below Normal	Starter Motor cannot be engaged.
444-6	Starter Motor Relay : Current Above Normal	Starter Motor cannot be engaged.
3467-3	Main Power Relay : Voltage Above Normal	The voltage is outside of the acceptable range, machine will not operate.
3467-5	Main Power Relay : Current Below Normal	The current is outside of the acceptable range, machine will not operate.
3467-6	Main Power Relay : Current Above Normal	The current is outside of the acceptable range, machine will not operate.
3627-3	Access Ladder Down Relay : Voltage Above Normal	The ladder will not lower when activated.
3627-5	Access Ladder Down Relay : Current Below Normal	The ladder will not lower when activated.
3627-6	Access Ladder Down Relay : Current Above Normal	The ladder will not lower when activated.
3628-3	Access Ladder Up Relay : Voltage Above Normal	The ladder will not raise when activated.
3628-5	Access Ladder Up Relay : Current Below Normal	The ladder will not raise when activated.
3628-6	Access Ladder Up Relay : Current Above Normal	The ladder will not raise when activated.

Implement ECM

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

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Table 2
Implement ECM (MID 82)
DTC	Code Description	System Response
1852-5	Air Conditioner Relay : Current Below Normal	Machine HVAC system will not function.
1852-6	Air Conditioner Relay : Current Above Normal	Machine HVAC system will not function.
2660-5	Air Conditioner Condenser Relay : Current Below Normal	Machine HVAC system will not function.
2660-6	Air Conditioner Condenser Relay : Current Above Normal	Machine HVAC system will not function.
2662-5	Cab Air Heater Engine Coolant Actuator : Current Below Normal	Machine HVAC system will not function.
2662-6	Cab Air Heater Engine Coolant Actuator : Current Above Normal	Machine HVAC system will not function.

Possible Causes and Schematics

Possible Causes for an FMI 3 Diagnostic code are:

The indicator lamp has failed.
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 circuit breaker for the subsystem is open.
The relay has failed.
The energize circuit of the relay is open or the circuit has a faulty connection.
The return circuit of the relay is open or the circuit has a faulty connection.
The ECM module 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	g03317197
Schematic of the Transmission/Chassis ECM J1 Relay Connections

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Illustration 2	g03317135
Schematic of the Transmission/Chassis ECM J2 Relay Connections

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Illustration 3	g03423955
Schematic of the HVAC control relays for the Implement ECM

Note: The diagrams above are simplified schematics of the relay circuits and the relay connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. For the complete schematic, refer to the latest revision of the electrical schematic. Reference the list below for your specific machine:

For Model 621K machines refer to Electric Schematic, UENR2689.

Diagnostic Trouble Code Procedure

Note: Poor harness connections are often the cause of a problem in electrical circuits. Before performing any troubleshooting procedure, inspect all of the connectors involved in the circuit. Verify that all of the connections in the circuit are dry, clean, secure, and in good condition. Each pin and socket in the connectors should mate correctly when the connectors are fastened together. Check for exposed wires at the connectors for nicks or abrasion. If a problem is found with any of the connections, correct the problem and verify that diagnostic code is still active, before performing the following procedures. For more information, refer to Troubleshooting, "Electrical Connector - Inspect".

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Table 3
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 4. FMI 6 diagnostic code, proceed to Test Step 6.
Begin Process For FMI 3 Troubleshooting HERE
2. Check The Relay. A. Turn the Key Start switch and the disconnect switch to the ON position. B. Observe the status of the active diagnostic code. C. Disconnect the relay from the machine harness. D. Refer to the schematic to identify the points for the coil and measure the resistance with a multimeter.	The coil should measure 27.5 ± 3 Ω at 20° C (68° F). When the relay is removed from the wiring harness, the active diagnostic code does not change.	OK- All of the checks of the relay are the same as the expected results. Proceed to Test Step 3. NOT OK- The observed diagnostic code was replaced with an FMI 5 code when the relay was removed from the wiring harness. Also the resistance check does not match the expected results. Repair- The relay has failed. Replace the faulty relay. After replacing the relay, verify that the new relay has corrected the problem before operating the machine. STOP
3. Check The Machine Harness For A Short A. Turn key start switch and disconnect switch OFF. B. Disconnect harness connection at the relay. C. If the relay is connected directly to an ECM, disconnect J1 and J2 connectors from ECM. D. Measure resistance of relay signal contact to all J1 and J2 connectors, if the relay is wired directly to an ECM.	Each reading is greater than 5K Ω.	OK - All resistance measurements are greater than 5K Ω. Proceed to Test Step 9. 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. Examine all of the connectors in the circuits for locations in the machine harness where the circuits could be shorted. 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
4. Check The Relay. A. Turn the disconnect switch and the key start switch to the OFF position. B. Disconnect the relay for the starter motor from the machine harness. C. At the machine harness connector for the relay, place a jumper wire from contact 2 to contact 3 of the relay. (These pins should correspond with the coil.) D. Turn the disconnect switch and the key start switch to the START position for a few seconds. E. Observe the status of the active diagnostic code.	The diagnostic code has changed from an active FMI 5 code to an FMI 6 code.	OK- The active code has changed from an FMI 5 to an FMI 6, when the jumper wire is installed. The relay is the cause of the problem. Repair- The relay has failed. Repeat the test step to confirm the failure of the relay. Measure the resistance across pins 2 and 3 of the relay (pins for the coil). The resistance along the pins of the properly working relay should be 27.5 ±3 Ω at 20° C (68° F). A resistance greater than the tolerance indicates a problem in the coil. Replace the relay. STOP NOT OK- The diagnostic code remains active after the jumper wire has been installed. The jumper wire did not change the status of the active diagnostic code. Proceed to Test Step 5.
5. Check The Relay Circuit For An Open. A. Remove the relay from the machine harness. B. Turn the key start switch and the disconnect switch to the OFF position. C. Disconnect the J1 and J2 connectors from the ECM module. D. At the machine harness connector measure the resistance from the signal contact for the relay to the ground contact. E. Observe the resistance on the multimeter as you wiggle the machine harness connectors for the ECM. Observe the resistance of the multimeter and wiggle the machine harness for the relay. Gently pull on the wires and wiggle the wires.	The resistance is less than 5 Ω at all times while the harness is manipulated.	OK- The resistance is less than 5 Ω. The machine harness is correct. Proceed to Test Step 9. NOT OK- The resistance is greater than 5 Ω. The machine harness is not correct. There could be an open connection or a poor connection in the harness circuit of the machine. Repair- A poor connection could be the cause of the problem. A connector may be loose, dirty, or corroded. Inspect the connectors in the circuit. Ensure that all connectors are clean, tight and in good condition. Follow the wiring harness to look for areas when the harness could be pinched. Repair or replace the wiring harness. 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 6 Troubleshooting HERE
6. Check The Relay. A. Turn the disconnect switch and the key start switch to the OFF position. B. Disconnect the suspected relay from the machine harness. C. Observe the status of the diagnostic code. Turn the disconnect switch to the ON position.	The failure mode identifier for the code changes from FMI 6 to FMI 5 when the procedure is followed.	OK- The failure mode for the active diagnostic code changes from FMI 6 to FMI 5 when the relay is disconnected. Repair- The relay has failed. Repeat this test to verify the results. Check the resistance of the coil of the relay. Measure the resistance across the pins of the coil (pin 2 and pin 3). The resistance of a functioning relay is 27.5 ± 3 Ω at 20° C (68° F). To cause this problem, the resistance must be less than the tolerance. After the relay is replaced, verify that the new relay corrects the problem. STOP NOT OK- The diagnostic code remains active. Disconnecting the relay did not change the status of the diagnostic code. Proceed to Test Step 7.
7. Check The Indicator Lamp. A. Turn the 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 8. NOT OK - The resistance is greater than 50 Ω. The relay has failed. Repair - Replace the relay. Note: After the relay is replaced, confirm the diagnostic code is no longer active. STOP
8. Check The 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 lamp relay contact and all ground contacts.	Each reading is greater than 5K Ω.	OK - All machine harness readings are correct. Proceed to Test Step 9. 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 greater than 5 Ω but less than 5K Ω indicates a loose or corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP
9. Check If The Diagnostic Code Remains. A. Turn the 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 AVSpare. This consultation may greatly reduce repair time. Follow the steps in Testing and Adjusting, "ECM - Replace" if the ECM needs to be replaced. STOP