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

Sensor Signal (Analog, Passive) - Test

621K OEM Wheel Tractor-Scraper [UENR5941]

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

621K OEM Wheel Tractor-Scraper Sensor Signal (PWM) - Test

ELECTRICAL AND STARTING SYSTEM

SENSOR GP

621K, 623K and 627K Wheel Tractor-Scrapers Speed Sensor - Test

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

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

621K OEM Wheel Tractor-Scraper Sensor Signal (PWM) - Test

621K OEM Wheel Tractor-Scraper Sensor Supply - Test

1.1. Implement ECM

2.1. Transmission/Chassis ECM

3.1. Diagnostic Trouble Code Procedure

Implement ECM

The following is a list of codes that are associated with the passive (analog) circuits of the machine.

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Table 1
Implement ECM (MID 82)
DTC	Code Description	System Response
600-3	Hydraulic Oil Temperature Sensor : Voltage Above Normal	The system cooling fan will be on constantly.
600-4	Hydraulic Oil Temperature Sensor : Voltage Below Normal	The system cooling fan may not turn on when needed.
779-3	Cab Air Temperature Sensor : Voltage Above Normal	System may not respond to requested changes.
779-4	Cab Air Temperature Sensor : Voltage Below Normal	System may not respond to requested changes.
2357-3	Air Conditioner Evaporator Coil Temperature Sensor : Voltage Above Normal	Operator will be alerted to fault.
2357-4	Air Conditioner Evaporator Coil Temperature Sensor : Voltage Below Normal	Operator will be alerted to fault.
2663-3	Cab Ventilation Duct Temperature Sensor : Voltage Above Normal	Operator will be alerted to fault.
2663-4	Cab Ventilation Duct Temperature Sensor : Voltage Below Normal	Operator will be alerted to fault.

Transmission/Chassis ECM

The following is a list of codes that are associated with the passive (analog) circuits of the machine.

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Table 2
Transmission/Chassis ECM (MID 27)
DTC	Code Description	System Response
826-3	Torque Converter Oil Temperature Sensor : Voltage Above Normal	When this diagnostic code occurs, there is no change in the system operation. The torque converter outlet oil temperature gage will not indicate the actual oil temperature.
826-4	Torque Converter Oil Temperature Sensor : Voltage Below Normal	When this diagnostic code occurs, there is no change in the system operation. The torque converter outlet oil temperature gage will not indicate the actual oil temperature.
830-3	Front Brake Oil Temperature Sensor : Voltage Above Normal	Operator will be alerted by the message system. Incorrect readings of the temperature will be displayed.
830-4	Front Brake Oil Temperature Sensor : Voltage Below Normal	Operator will be alerted by the message system. Incorrect readings of the temperature will be displayed.
4254-3	Front Brake/Transmission Oil Temperature Sensor : Voltage Above Normal	The temperature will indicate a temperature that is lower than the actual temperature.
4254-4	Front Brake/Transmission Oil Temperature Sensor : Voltage Below Normal	The temperature will indicate a temperature that is higher than the actual temperature.

The tables below are a reference that can be used when checking the resistance of the temperature sensors listed in the table above.

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Table 3
Temperature Conversion Chart for the Torque Converter Oil Temperature Sensor, and Transmission Oil Temperature Sensor
Celsius Temperature	Fahrenheit Temperature	Resistance At Temperature
−40° C	−40° F	33650.2Ω
−30° C	−22° F	17709.4Ω
−20° C	−4° F	9716.7Ω
−10° C	14° F	5538.0Ω
0° C	32° F	3268.3Ω
10° C	50° F	1991.4Ω
20° C	68° F	1249.5Ω
30° C	86° F	805.5Ω
40° C	104° F	532.3Ω
50° C	122° F	360.0Ω
60° C	140° F	248.7Ω
70° C	158° F	175.2Ω
80° C	176° F	125.7Ω
90° C	194° F	91.7Ω
100° C	212° F	68.0Ω
110° C	230° F	51.2Ω
120° C	248° F	39.0Ω
130° C	266° F	30.1Ω
140° C	284° F	23.6Ω
150° C	302° F	18.6Ω

Possible Causes for an FMI 3 Diagnostic code are:

The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to another circuit.
The sensor 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 for the sensor is shorted to ground.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g03350540
Schematic of the passive sensors for the model 621K OEM Wheel Tractor machines associated with the Implement ECM.

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Illustration 2	g03318441
Schematic of the passive sensors for the model 621K OEM Wheel Tractor machines associated with the Transmission/Chassis ECM.

Note: The illustrations above are simplified schematics of the ECM connections. The schematics are 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.

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

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 4
Troubleshooting Test Steps	Values	Results
1. Identify The Active DTC Code Associated With The Suspect Circuit.	Code present.	FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 5.
Begin Process For FMI 3 Troubleshooting HERE
2. Check For Voltage At The Sensor. A. Turn the key start switch and the disconnect switch to the ON position. B. Disconnect the sensor from the machine harness. C. At the machine harness connector for the sensor, measure the voltage between contact 1 and 2.	The voltage should measure 5 ±0.3 VDC.	OK - The voltage is 5 ±0.3 VDC. Proceed to Test Step 3. NOT OK - The voltage is not within the tolerance expected at 5 VDC. Repair- There is a problem with the machine harness or the ECM has failed. A failure of the ECM is unlikely. Proceed to Test Step 4.
3. Check For An Open In The Sensor Circuit. A. Turn the key start switch and disconnect switch to the OFF position. B. Disconnect the J1 and J2 machine harness connectors from the ECM. C. At the machine harness connector for the sensor, install a jumper wire from contact 1 to contact 2. D. At the harness connector for the sensor, measure the resistance from the signal contact to all possible connections of the negative battery. .Refer to the electrical schematic for your machine for more information about the circuits. (See above.) E. At the harness connector for the ECM measure the resistance at the contacts for the sensor.	The resistance reading is less than 5 Ω.	OK - The resistance is less than 5 Ω. Proceed to Test Step 4. NOT OK - The resistance is greater than 5K Ω. There is an open in the machine harness somewhere between the ECM and sensor in the sensor supply circuit. Repair: Repair or replace the 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
4. Check The Signal Circuit For A Short. A. The disconnect switch and the key start switch remain in the OFF position. B. The J1 and J2 ECM connectors remain disconnected. C. Remove the jumper wire that was installed for the previous step at the machine harness connector for the sensor between contacts 1 and 2. D. At the machine harness connectors for the ECM, measure the resistance between the sensor signal circuit and all other J1 and J2 contacts.	Each resistance reading is greater than 5KΩ.	OK - Each resistance measurement is greater than 5K Ω. The sensor has failed. Repair: Replace the sensor and verify that the new sensor corrected the problem. If the problem persists, exit this procedure and perform this procedure again. NOT OK - Any resistance measurement less than 5K Ω. There is a short in the machine harness somewhere between the sensor signal circuit wire and the circuit with the low resistance measurement. Repair: Repair the harness or replace the harness. STOP
Begin Process For FMI 4 Troubleshooting HERE
5. Check The Sensor A. Turn key start switch and disconnect switch ON. B. Ensure that the diagnostic code is active. C. Disconnect the sensor from the machine harness. Observe the status of the diagnostic code.	The diagnostic trouble code remains active.	OK - Diagnostic code remains active and does not change. Proceed to Test Step 6. NOT OK - The diagnostic code is no longer active. The sensor has failed. Repair: Replace the sensor. STOP
6. Check The Wiring Harness Of The Sensor For A Short To Ground. A. Turn the key start switch and the disconnect switch OFF. B. Disconnect machine harness connection at the sensor. C. Disconnect machine harness connections J1 and J2 from the ECM. D. At the machine harness connector for the ECM, measure resistance from the signal contact of machine harness to all possible sources of ground. Measure resistance to all contacts of machine harness connectors for the ECM.	Each reading greater than 5K Ω.	OK - All resistance readings are greater than 5K Ω. Proceed to Test Step 7. NOT OK - One or more of the 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. STOP
7. Check If The Diagnostic Code Remains. A. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing. B. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit. C. Reconnect all of the harness connectors to make sure that the connectors are fully seated. Observe that the clips for each connector are fastened securely. D. Turn the key start switch and the disconnect switch ON. E. Clear all diagnostic codes. F. Operate the machine. G. Stop the machine and engage safety lock lever. H. Check if diagnostic code for the sensor is active.	Diagnostic trouble code is no longer active.	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. Note: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors. Resume normal machine operation. NOT OK - Diagnostic trouble code has not been corrected. Repair: If the diagnostic code has not been corrected after performing the procedure a second time, follow the procedure below for replacing the ECM. 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