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

Sensor Signal (Analog, Active) - Test

621K OEM Wheel Tractor-Scraper [UENR5941]

621K OEM Wheel Tractor-Scraper Relay - Test

621K OEM Wheel Tractor-Scraper Sensor Signal (Analog, Passive) - 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. Transmission/Chassis ECM

2.1. Troubleshooting Procedure

Transmission/Chassis ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the active (analog) circuits of the machine.

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Table 1
Transmission/Chassis ECM (MID 27)
DTC	Code Description	System Response
96-3	Fuel Level Sensor : Voltage Above Normal	Fuel level indicator will not display accurately.
96-4	Fuel Level Sensor : Voltage Below Normal	Fuel level indicator will not display accurately.
2987-3	Brake Charge Pressure Sensor #1 : Voltage Above Normal	Indicator for low brake pressure may be active.
2987-4	Brake Charge Pressure Sensor #1 : Voltage Below Normal	Indicator for low brake pressure may be active.

Possible Causes for an FMI 3 Diagnostic code are:

The power supply circuit for the sensor is open.
The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the sensor power supply.
The sensor has failed.
The sensor was activated in Cat ET when the component is not on the machine.
The Transmission/Chassis ECM has failed. This situation 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 Transmission/Chassis ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g03318750
Schematic for the Analog, Active Sensors associated with the Transmission/Chassis ECM.

Note: The diagram above is simplified schematic of the ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision for the complete schematic.

Note: Before performing 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. Refer to the list below to identify the correct schematic for your machine.

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 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 2
Troubleshooting Test Steps	Values	Results
1. Identify Active DTC Code Associated With Sensor 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 The Supply Voltage At The Sensor. A. Turn key start switch and disconnect switch ON. B. Disconnect the machine harness from sensor. C. Refer to the schematic to determine the voltage source for the suspected faulty sensor. D. Measure voltage between supply and return contacts at the machine harness connector for the sensor.	Voltage is 5 ± 0.3 VDC or 10 ± 0.5 VDC.	OK - The voltage reading is correct for the suspected faulty sensor. Proceed to Test Step 3. NOT OK- The voltage is NOT correct for the circuit. Repair - If there is an active troubleshooting code for the supply voltage, correct that problem. Check the return circuit or the supply circuit for a bad connection or open in the machine harness. Check the condition of all connectors and repair as necessary. STOP
3. Check For An Open In The Sensor Circuit. A. The sensor remains disconnected from the machine harness. B. Turn the key start switch and the disconnect switch OFF. C. At the harness connector for the sensor, place a jumper wire between the signal contact and the return contact. D. Disconnect J1 and J2 harness connectors from the ECM. E. At machine harness connector for ECM, measure the resistance from the signal contact for the sensor to the return contact. F. Gently pull on the wire and move the wire in a circular motion at ECM connector and observe the resistance readings. Repeat the process for the sensor connector.	The resistance is less than 5 Ω at all times during the manipulation of the harness.	OK - The resistance is less than 5 Ω. The signal circuit and the ground circuits of the sensor are not open in the machine harness. Proceed to Test Step 4. NOT OK - Resistance reading for the signal circuit or the return circuit is greater than 5K Ω. Repair: Check the signal circuit or the ground circuit for opens or bad connections. 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 Signal Circuit For A Short To +Battery. A. The Sensor and the ECM are disconnected from the harness. B. Turn the disconnect switch and the key start switch OFF. C. Remove the jumper wire installed in the previous step. D. Measure the resistance between the signal wire and all other wires used in the J1 and J2 harness connectors.	Resistance greater than 5K Ω for all readings.	OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 5. NOT OK- The resistance less than 5 Ω. Repair: A short exists in the harness between the +battery and signal circuit. 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
5. Check The Sensor. A. Turn the disconnect switch and the key start switch to the ON position. B. Ensure that the diagnostic code is active. C. With FMI 4 active, disconnect the sensor from the machine harness. D. Observe Cat ET or the operator monitor for code change as the sensor is disconnected and connected to harness.	The FMI 4 diagnostic code remains active.	OK - The diagnostic code remains active. The sensor is correct. Proceed to Test Step 6. NOT OK - The diagnostic code is no longer active. The sensor has failed. Replace the entire sensor. STOP
6. Check The Signal Circuit For A Short To Ground. A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the machine harness from the sensor. C. Disconnect the J1 and J2 harness connectors from the ECM. D. Measure the resistance between the signal contact for sensor and all possible sources of ground. Measure the resistance to all contacts used in the J1 and J2 harness connectors.	The resistance is greater than 5K Ω.	OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 7. NOT OK - One or more resistance measurements are not correct. A short circuit exists between frame ground and the signal circuit or within the machine harness. Repair: Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω indicates a loose connection or a corroded connection in the circuit. A resistance measurement greater than 5K Ω would indicate an open in the circuit. STOP
7. Check If The Diagnostic Code Remains. A. Turn the key start switch and the disconnect switch ON. B. Clear all diagnostic codes. C. Operate the machine. D. Stop machine and engage the safety lock lever. E. Check if the diagnostic code for the sensor is active.	The code for the sensor is NO longer present.	OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by a poor electrical connection or a short at one of the harness connections. Resume machine operation. STOP NOT OK - The diagnostic trouble code has not been corrected. Repair: Recheck the circuit and perform this procedure again. If the diagnostic code is still active, 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. Follow the procedure in Testing and Adjusting, "ECM - Replace" to replace the ECM. STOP