621K OEM Wheel Tractor-Scraper Switch Circuits

Switch Circuits - Test

621K OEM Wheel Tractor-Scraper [UENR5941]

621K OEM Wheel Tractor-Scraper Solenoid Valve - Test

621K OEM Wheel Tractor-Scraper Wiring Harness (Open Circuit) - 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. Implement ECM

2.1. Transmission/Chassis ECM

3.1. Troubleshooting Procedure

Implement ECM

Show/hide table

Table 1
Implement ECM (MID 82)
DTC	Description	System Response
874-3	Mode Select Switch : Voltage Above Normal	Hydraulic systems will be effected.
874-4	Mode Select Switch : Voltage Below Normal	Hydraulic systems will be effected.
1293-3	Cushion Switch : Voltage Above Normal	The diagnostic code will cause the cushion-hitch switch to be inoperative. The cushion-hitch switch will remain in the last state.
1293-4	Cushion Switch : Voltage Below Normal	The diagnostic code will cause the cushion-hitch switch to be inoperative. The cushion-hitch switch will remain in the last state.
2659-2	Cab Air Temperature Control Switch : Data Erratic, Intermittent, or Incorrect	Signal from switch circuit is erratic, intermittent, or Incorrect.
2661-3	Cab Air Temperature Control : Voltage Above Normal	Output will not change after adjustment attempted.
2661-4	Cab Air Temperature Control : Voltage Below Normal	Output will not change after adjustment attempted.
3603-3	Auto/Manual Switch : Voltage Above Normal	Unable to change mode from last position.
3603-4	Auto/Manual Switch : Voltage Below Normal	Unable to change mode from last position.

Transmission/Chassis ECM

Show/hide table

Table 2
Transmission/Chassis ECM (MID 27)
DTC	Description	System Response
70-2	Parking Brake Switch : Data Erratic, Intermittent, or Incorrect	Parking brake switch will fail to function.
1292-3	Push Switch (Transmission Hold) : Voltage Above Normal	Switch fails to operate when activated.
1292-4	Push Switch (Transmission Hold) : Voltage Below Normal	Switch fails to operate when activated.
3797-3	Operator Seat Belt Switch : Voltage Above Normal	Circuit will be active in both positions.
3797-4	Operator Seat Belt Switch : Voltage Below Normal	Circuit will be inactive in both positions.

Possible Causes for an FMI 2 Diagnostic code are:

One of the wires for the NORMALLY CLOSED (N/C) connections is OPEN or grounded.
The wire for the NORMALLY OPEN (N/O) circuit connection is OPEN or grounded.
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.
The signal is permanently closed.
The switch has failed.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 4 diagnostic code are:

The signal circuit in the machine harness is shorted to ground.
The switch has failed.
The ECM has failed. A failure of the ECM is unlikely.

Show/hide table

Table 3
Status of Parking Brake Switch
Mode	Switch Position	Wire U734-GN (Normally Open)	Wire F780-PK/ U735-GY (Normally Closed)
Brake ON	Rocked UP	Closed	Open
Brake OFF	Rocked DOWN	Open	Closed

Show/hide table

Table 4
Status of Operator Seat Belt Switch
Mode	Switch Position	Wire U730-BR (Normally Open)	Wire U729-PU (Normally Closed)
Switch ON	Rocked DOWN	Closed	Open
Switch OFF	Rocked UP	Open	Closed

Show/hide table




Illustration 1	g03336412
Switch Connections for the Transmission/Chassis ECM

Show/hide table




Illustration 2	g03350820
Switch Connections for the Implement ECM

Note: The diagram above is a simplified schematic of the Transmission/Chassis ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic for your specific machine. Refer to the list below to identify the correct schematic for your machine.

Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear the diagnostic trouble codes when the original diagnostic trouble code has been corrected.

Electrical Schematic, UENR2689 for the 621K Tractor/Scraper.

Troubleshooting 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 (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".

Show/hide table

Table 5
Troubleshooting Test Steps	Values	Results
1. Identify The Active FMI Code Associated With The Switch 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 Troubleshooting for FMI 2 Diagnostic Code Here
2. Check The NORMALLY CLOSED Circuit For Proper Operation. A. Turn the disconnect switch and the key start switch OFF. B. Disconnect the machine harness from the ECM. C. Measure the resistance between the NORMALLY CLOSED (N/C) and one of the NORMALLY OPEN (N/O) pins on the ECM. The measurement is made at the harness connector for the ECM. D. Toggle the switch and verify continuity. Refer to Table 4.	The resistance should be less than 5 Ω when switch operation indicates continuity, and greater than 5K Ω when switch operation indicates no continuity.	OK - The resistance is as expected. Proceed to Test Step 4. NOT OK - The resistance is not as expected. Proceed to Test Step 3.
3. Check The NORMALLY CLOSED Circuit Of The Switch. A. Turn the disconnect switch and the key start switch OFF. B. Disconnect the switch from the machine harness. C. At the connector for the switch, measure the resistance between contact 2 and contact 1. Toggle the switch and observe the results. D. At the connector for the switch, measure the resistance between contact 2 and contact 3. Toggle the switch and observe the results. E. At the connector for the switch, measure the resistance between contact 4 and contact 5. Toggle the switch and observe the results. F. At the connector for the switch, measure the resistance between contact 6 and contact 5. Toggle the switch and observe the results.	With the switch in the ON position, the resistance should measure more than 5K Ω. With the switch in the OFF position, the resistance should measure less than 5 Ω.	OK - With the switch in the ON position, the resistance is more than 5K Ω. With the switch in the OFF position, the resistance is less than 5 Ω. Repair- The machine harness has failed. Based on observations the suspect wire can be determined. Either one of the NORMALLY CLOSED circuits is open or grounded in the machine harness. Another possibility is that the NORMALLY CLOSED circuit or the return circuit is open or grounded. Repair the machine harness or replace the machine harness. Proceed to Test Step 11 to confirm the fault has been corrected. NOT OK - The switch has failed. Repair- Replace the switch. Verify that the new switch corrects the problem. STOP
Begin Process For FMI 3 Troubleshooting HERE
4. Check The Ground Circuit For An Open. A. Turn the disconnect switch and the key start switch OFF. B. Disconnect the switch from the machine harness. C. Use a jumper wire between each contact on the machine harness at the switch end, one at a time. D. Measure the resistance at the corresponding ECM harness pins.	The resistance is less than 5 Ω.	OK - The resistance is less than 5 Ω. Proceed to Test Step 5. NOT OK - The resistance is greater than 5K Ω. Repair: The circuit wire is open in the machine harness. 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
5. Check The Circuit For A Short. A. The harness connectors for the switch and ECM remain disconnected. B. Remove any jumper wires used from a previous test step. C. At the machine harness connector for the ECM measure the resistance between the signal circuits and every other contact in the wiring harness.	The resistance is greater than 5K Ω.	OK - The resistance check is correct. Proceed to Test Step 6. 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. STOP
6. Check the Ground Circuit Of The Switch In The Harness. A. Turn key start switch and disconnect switch OFF. B. Disconnect the switch from the machine harness. C. Measure the resistance between the return contact on the harness to ground.	The resistance is less than 5 Ω.	OK - The circuit is correct. Proceed to Test Step 7. 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 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 The Switch. A. Measure the resistance from the normally open contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes. B. Measure the resistance from the normally closed contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes.	Open resistance should be greater than 5K Ω. Closed resistance should be less than 5 Ω. These values should reverse when the switch is engaged.	OK - The measurements are correct. Proceed to Test Step 8. NOT OK - One or more of the measurements was incorrect. Repair: Replace the switch. Verity that the new switch corrects the diagnostic code. 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 The Signal Circuits For An Open. A. Reconnect the switch to the machine harness. B. Perform the same test performed in Test Step 7. However instead of measuring resistance from the switch contacts, measure from the corresponding contacts on the ECM harness.	Open resistance should be greater than 5K Ω. Closed resistance should be less than 5 Ω. These values should reverse when the switch is engaged.	OK - The measurements are correct. Note: If testing the Horn Switch, refer to Troubleshooting, "Relay - Test". Proceed to Test Step 11. NOT OK - One or more of the measurements was incorrect. 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. STOP
Begin Process For FMI 4 Troubleshooting HERE
9. Check The Switch. A. Measure the resistance from the normally open contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes. B. Measure the resistance from the normally closed contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes.	Open resistance should be greater than 5K Ω. Closed resistance should be less than 5 Ω. These values should reverse when the switch is engaged.	OK - The measurements are correct. Proceed to Test Step 10. NOT OK - One or more of the measurements was incorrect. Repair: Replace the switch. Verity that the new switch corrects the diagnostic code. 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
10. Check The Signal Circuits For An Open. A. Reconnect the switch to the machine harness. B. Perform the same test performed in Test Step 6. However instead of measuring resistance from the switch contacts, measure from the corresponding contacts on the ECM harness.	Open resistance should be greater than 5K Ω. Closed resistance should be less than 5 Ω. These values should reverse when the switch is engaged.	OK - The measurements are correct. Proceed to Test Step 11. NOT OK - One or more of the measurements was incorrect. 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. STOP
11. Check If The Diagnostic Code Remains. A. Inspect the harness connectors and clean the contacts of the harness connectors. B. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit. C. Reconnect all harness connectors. D. Turn key start switch and disconnect switch ON. E. Operate the machine. F. Check the status of the diagnostic code.	The diagnostic code is not active.	OK - The diagnostic code is still active. Repair: Check the status of the diagnostic code. If the cause of the problem is not found, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with AVSpare. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "ECM - Replace" STOP NOT OK - The continuity check is not correct. Repair: There is an open in the signal circuits of the machine harness. Repair or replace the machine harness. STOP