D7E Track-Type Tractor Caterpillar

Speed Sensor - Test - Motor Speed Sensor

Usage:

D7E HKA

Motor ECM

Two speed sensors are used to monitor the operation of the Electric Drive Motor 2. Each of the speed sensors provides two frequency input signals to the Motor ECM on separate "signal A" and "signal B" circuits. A phase shift is present between the two speed sensor signals that enable the Motor ECM to determine the direction of rotation of the drive motors in addition to the rotational speed of the motors.

For control purposes, the ECM assumes that the Electric Drive Motor 1 speed and direction are the same as the Electric Drive Motor 2.

The Motor ECM uses the input signals from either Motor Speed Sensor 1 or Motor Speed Sensor 2 to monitor the drive motors.

When the machine is first put into forward or reverse, the Motor ECM will determine whether the Motor Speed Sensor 1 or the Motor Speed Sensor 2 will be used to monitor motor speed. If the ECM detects that there is a problem with one of the sensor circuits, the ECM will monitor the input from the other sensor. If no problem is detected from either speed sensor, the ECM can choose either one to be the monitored sensor.

Note: : If the Motor ECM has activated diagnostic codes for both of the Motor ECM Motor Speed Sensor #1 signal circuits (CID 3271, CID 3272) at the same time, the most likely cause is either the sensor has failed, the power supply has been interrupted, or there is a problem with one of the harness connectors that is close to the sensor. Investigate these possibilities first if both of the signal circuit diagnostic codes are active.

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Table 1
Motor ECM
DTC	Code Description	System Response
3271-3	Drive Motor Speed Sensor 1 Signal 1: Voltage Above Normal	A level 1 fault will be registered.
3271-4	Drive Motor Speed Sensor 1 Signal 1: Voltage Below Normal	A level 1 fault will be registered.
3271-8	Drive Motor Speed Sensor 1 Signal 1: Abnormal Frequency, Pulse Width, or Period	A level 1 fault will be registered.
3272-3	Drive Motor Speed Sensor 1 Signal 2: Voltage Above Normal	A level 1 fault will be registered.
3272-4	Drive Motor Speed Sensor 1 Signal 2: Voltage Below Normal	A level 1 fault will be registered.
3272-8	Drive Motor Speed Sensor 1 Signal 2: Abnormal Frequency, Pulse Width, or Period	A level 1 fault will be registered.
3273-3	Drive Motor Speed Sensor 2 Signal 1: Voltage Above Normal	A level 1 fault will be registered.
3273-4	Drive Motor Speed Sensor 2 Signal 1: Voltage Below Normal	A level 1 fault will be registered.
3273-8	Drive Motor Speed Sensor 2 Signal 1: Abnormal Frequency, Pulse Width, or Period	A level 1 fault will be registered.
3274-3	Drive Motor Speed Sensor 2 Signal 2: Voltage Above Normal	A level 1 fault will be registered.
3274-4	Drive Motor Speed Sensor 2 Signal 2: Voltage Below Normal	A level 1 fault will be registered.
3274-8	Drive Motor Speed Sensor 2 Signal 2: Abnormal Frequency, Pulse Width, or Period	A level 1 fault will be registered.

Note: If there is a DTC active for both sensor 1 and sensor 2, an EID 2169 will become active and the Power Train will be disabled.

Possible causes for an FMI 3 diagnostic code are:

The speed sensor has failed.
The speed sensor circuit is shorted to a voltage source in the machine harness.
The sensor signal circuit is open or has a loose connection.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 4 diagnostic code are:

The Speed Sensor has failed.
The speed sensor circuits are shorted to ground.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 8 diagnostic code are:

The sensor has failed or is improperly installed.
Intermittent connections or poor connections.
The Ring-Magnetic (Magnetic target wheel) is damaged or improperly installed.
The ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g03704989
Schematic of the Speed Sensor circuits

Note: The diagram above is a simplified schematic of the connections for the speed sensor circuits. 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 the specific machine being serviced for the complete schematic.

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Illustration 2	g03756356
The above illustration shows the left side of the propulsion module and the following components: (1) Primary Drive Motor Speed Sensor for the Motor ECM (1) (2) Secondary Drive Motor Speed Sensor for the Motor ECM (2)

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Illustration 3	g03756359
(3) Location of the Ring-Magnetic (Magnetic target wheel)

Diagnostic Trouble Code Procedure

Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this 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 the diagnostic code is active before performing a troubleshooting procedure. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.

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Table 2
FMI 3, FMI 4, And FMI 8 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Safe Shutdown Procedure This procedure must be performed before service is performed in an area that is in the vicinity of Power Train hazardous voltage components and conductors to ensure the DC power bus voltage and the Accessory Power bus voltage has discharged properly B. Refer to the Troubleshooting, "Electrical Maintenance Guidelines" section of this manual. Perform the "Safe Shutdown Procedure for Electric Drive Tractors" before proceeding with the following troubleshooting steps.	The Safe Shutdown Procedure for Electric Drive Tractors has been performed.	OK - The Safe Shutdown Procedure for Electric Drive Tractors has been performed. The Power Train system and the Accessory Power system for the machine can now be serviced. This procedure should not require the disconnection of any of the hazardous voltage connectors. However, if an AC connection enclosure is opened or if a hazardous voltage DC connector is disconnected, a multi-meter must be used to check for DC voltage between all exposed conductors and frame ground. Do not make personal contact with the exposed conductors until you have manually measured for voltage between ground and the conductors. Verify that there is less than 50.0 VDC present between all exposed AC or DC hazardous voltage conductors and frame ground before any other action is taken. Proceed to Test Step 2.
2. Check For A Short In The Sensor Signal Circuit A. Disconnect the machine harness connector J1 from the ECM. B. At the J1 machine harness connector for the ECM, measure the resistance between the speed sensor signal circuit contact and a good frame ground. C. At the J1 machine harness connector for the ECM, measure the resistance between the speed sensor signal circuit contact and each of the other circuit contacts in the J1 harness connector for the ECM.	Each resistance measurement between the signal sensor circuit and the circuits used in the J1 connectors for the ECM is greater than 5 K Ω	OK - Each resistance measurement between the signal sensor circuit and the circuits used in the J1 connectors for the ECM is greater than 5 K Ω. The resistance measurements indicate the speed sensor circuits are not shorted to another circuit in the machine harness. Proceed to Test Step 3. NOT OK- One or more of the resistance measurements is less than 5 K Ω. There is a short in the machine harness. Repair: The short is between the signal speed sensor circuit and the circuit that measured the low resistance measurement. Refer to the complete machine Electrical System Schematic. Examine all of the connectors in the suspect speed sensor circuit for points in the machine harness where the circuits may be shorted. For information on testing for short circuits and finding short circuits, "Wiring Harness (Short Circuit) - Test". Repair or replace the machine harness. Proceed to Test Step 6.
3. Check The Power Supply A. Turn the key switch and the disconnect switch to the ON position. B. Use a multimeter to measure the ECM power supply voltage between the harness connector positive contact (wire E472-GN) and the negative contact (wire 233-BK).	The voltage should measure 12.0 ± 1.0 VDC.	OK - The voltage measures 12.0 ± 1.0 VDC. Proceed to Test Step 4. NOT OK - The sensor power supply voltage does not measure 12.0 ± 1.0 VDC. The power supply is not correct. Stop this procedure and determine the cause of the incorrect ECM power supply.
4. Check For An Open In The Sensor Signal Circuit A. The key switch and the disconnect switch remain in the OFF position. B. Disconnect the machine harness connector from the Motor Speed Sensor. C. Disconnect the machine harness connector J1 from the Motor ECM. D. Examine the pins and sockets on the speed sensor harness connector and on the speed sensor connector. Ensure all of the pins and sockets are secured in the connectors, the contacts are clean, and the contacts are in good condition. E. At the machine harness connector for the speed sensor, connect a jumper wire between the signal A contact 3 and the return circuit contact 2. F. At the machine harness connector J1 for the Motor ECM, measure the resistance between the signal contact and the return circuit contact. G. While observing the resistance measurement, wiggle the machine harness connector for the Motor ECM and wiggle the machine harness connector for the speed sensor. Gently pull on the wires and move the wires around. Do not disconnect the jumper wire.	The resistance measurement is less than 5.0 Ω at all times during the manipulation of the harness and the connectors.	OK - The resistance measurement is less than 5.0 Ω.The resistance measurement for the speed sensor circuit and the return circuit does not indicate there is an open in the machine harness. Proceed to Test Step 5. NOT OK - The resistance is greater than 5.0 Ω at all times or part of the time during the manipulation of the machine harness. There is an open or a poor connection in the signal speed sensor signal circuit or the return circuit. Repair: Check the signal circuit and the return circuit individually to determine which circuit has the open or the poor connection. Resistance greater than 5.0 Ω but less than 5 K Ω may indicate that one of the connection points in the circuit is not open but is not a good connection. A resistance measurement that is greater than 5 KΩ may indicate that a wire is either not connected or is open. Refer to the complete machine Electrical System Schematic. Check all of the connectors that are in the suspect speed sensor signal circuit. Ensure that all connections are clean, secure and in good condition. Repair or replace the machine harness. Proceed to Test Step 6.
5. Check The Speed Sensor Swap Speed Sensors to Check Sensors. A. Turn the key switch and the disconnect switch to the OFF position. B. At the speed sensor, use a length of tape or other means to mark both the machine harness connector and Motor Speed Sensor 1. Disconnect the marked machine harness connector from the Motor Speed Sensor 1. C. Disconnect the machine harness connector for Motor Speed Sensor 2 and reconnect the connector on the disconnected marked Motor Speed Sensor 1. D. Reconnect the marked connector for the Motor Speed Sensor 1 to the disconnected Motor Speed Sensor 2. E. Verify that the marked machine harness connector for the Motor Speed Sensor 1 is now connected to the Motor Speed Sensor 2. Verify that the unmarked machine harness connector for the Motor Speed Sensor 2 is now connected to the marked Motor Speed Sensor 1. F. Turn the disconnect switch to the ON position G. Start the Engine. Safely move the machine a short distance with travel speed above 0.4. Use the message display to view travel speed.	The DTC did not move with the sensor.	OK - The DTC did not move with the sensor. The Motor Speed Sensor is not causing the problem. Proceed to Test Step 6. NOT OK - The DTC moved with the sensor. This condition indicates that the Motor Speed Sensor has failed. Repair: Replace the faulty sensor. Proceed to Test Step 6.
6. Check The Magnetic Speed Wheel An FMI 8 can indicate an issue with the magnetic speed wheel. A. Remove the speed sensors and inspect the magnetic speed wheel for debris which may affect operation. B. Turn the key start switch and the disconnect switch ON. C. Clear all DTCs. D. Operate the machine. E. Stop the machine and engage the parking brake. F. Check if the diagnostic code is active.	The magnetic speed wheel is free from debris.	OK - The magnetic speed wheel is free from debris. Proceed to Test Step 7. NOT OK -Compressed air may be used to blow dry the sensor ring and remove any small magnetic particles that may cling to the Permalloy coating. Aerosol or liquid solvents or Isopropyl Alcohol should not be used. If the issue persists, there may be an issue with the wheel itself. Replace the wheel. Proceed to Test Step 7.
7. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch ON. C. Clear all DTCs. D. Operate the machine. E. Stop the machine and engage the parking brake. F. Check if the diagnostic code is active.	The DTC is no longer present.	OK - The DTC does not exist at this time. The initial DTC may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. . NOT OK - The DTC is still active. The problem that is causing the ECM to activate the diagnostic code has not been corrected. Proceed to Test Step 8.
8. Flash The Latest Software To The ECM A. ECM software causing this problem is unlikely. However, flash the latest version of ECM software to the Motor ECM to eliminate software as a possible cause. B. To flash the latest software to the ECM, refer to the "ECM Software - Install" procedure that is in this manual. After completing the flash program procedure, return to this procedure and proceed to the next step. C. After the latest version of ECM software has been flashed to the Motor ECM, turn the key switch to the OFF position. D. Start the Engine. Run the engine at low idle. E. Check if the DTC is active.	The DTC is not active. No new DTCs or EIDs have been activated.	OK - The DTC is no longer active and no new DTC or EIDs have been activated. Resume normal machine operation. NOT OK - The DTC has been activated again by the ECM. The new software program has not corrected the problem. Proceed to Test Step 9.
9. Swap ECMs To Resolve Issue A. The Generator ECM and Motor ECM can be interchanged to aid in troubleshooting. Refer to "ECM Swap - Test" in this manual. B. Operate the machine. C. Stop the machine and engage the parking brake. D. Check if the DTC is active.	The DTC is no longer active after the ECM swap. The ECM swap resolved the issue.	OK - The DTC is no longer active. The ECM swap resolved the issue. Resume normal machine operation. NOT OK - The DTC is active on the new ECM in the original location. The problem is not related to the ECM. If all of the above troubleshooting steps have been completed, contact the dealership Technical Communicator to consult with the Cat Dealer Solutions Network (DSN). Indicate the steps that have been taken to find the cause of the problem. The DSN will contact qualified company personnel that can make further recommendations.