CS54B, CP54B and CS64B Vibratory Soil Compactors Machine Electronic Control System Caterpillar

Speed Sensor (Dual Signal) - Test

Usage:

Machine ECM

The following is a list of diagnostic codes (SPN) associated with the Speed Sensors of the machine.

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Table 1
Machine ECM (MID 39)
SPN-FMI	Code Description	System Response
1595-5	Rear Axle, Right Wheel Speed: Current below normal	UCMD is Disabled, Limited to Low Axle Speed, Vibe Disabled Fault Level - 2
1595-8	Rear Axle, Right Wheel Speed: Abnormal frequency, pulse width, or period	UCMD is Disabled, Limited to Low Axle Speed, Vibe Disabled Fault Level - 2

Possible causes for an FMI 5 diagnostic code are:

The signal circuit of the speed sensor is open.
The speed sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 8 diagnostic code are:

The sensor has failed.
The spacing of the sensor is incorrect.
The signal circuit of the speed sensor is open.
Intermittent connections or poor connections.
Mechanical devices are loose.
Incorrect software is loaded to the ECM.
The ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g06251191
Speed Sensor (Dual Signal) connections

The diagram above is a simplified schematic of the System Voltage Machine ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown.

For the full Electrical Schematic of the Soil Compactors in this manual, refer to the Electrical Schematic, UENR6390.

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.

Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.

FMI 5 diagnostic code, proceed to Table 2.
FMI 8 diagnostic code, proceed to Table 3.

Note: Examine the Motor Speed Ring for damage or slippage on the shaft.

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Table 2
FMI 5 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check For Power At The Sensor A. Do not disconnect the harness connector from the sensor. B. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the voltage supply wire. C. Turn the key start switch and the disconnect switch to the ON position D. Measure the voltage from contact to frame ground.	The voltage is 8 ± 1.0 VDC.	OK - The voltage is 8 ± 1.0 VDC. Proceed to Test Step 2. NOT OK - The voltage is not 8 ± 1.0 VDC. The circuit is open or grounded. Repair- Repair the machine harness or replace the machine harness. Proceed to Test Step 5.
2. Check The Signal Circuit For An Open A. The key start switch and the disconnect switch remain in the OFF position. B. Disconnect the speed sensor from the machine harness. C. Disconnect the machine harness connectors from the ECM. D. At the speed sensor harness connector, insert a jumper wire between the signal and return wires. E. At the ECM harness connector, measure the resistance between the signal contact and the return contact.	The resistance value is less than 5 Ω.	OK - The resistance value is less than 5 Ω. The harness is correct. Proceed to Test Step 3. NOT OK - The resistance is greater than 5K Ω. There is an open circuit in the signal circuit or the return circuit. Note: A resistance greater than 5 Ω but less than 5KΩ indicates a loose connection or corroded connection in the circuit. A resistance value that is greater than 5K Ω would indicate an open in the circuit. Repair: Repair or replace the machine harness. Proceed to Test Step 5.
3. Check The Signal Of The Sensor A. Block up the machine in order to allow drum/wheel to rotate. B. Turn the key start switch and the disconnect switch to the OFF position. C. At the back of the harness connector for the sensor, remove the 7X-1710 Multimeter Probe from the previous step and insert the probe along the signal wire. D. At the back of the harness connector for the sensor, insert the 7X-1710 Multimeter Probe along the ground wire. E. Turn the disconnect switch and the key start switch to the ON position. F. Monitor the duty cycle signal of the sensor with the 146-4080 Digital Multimeter . G. Operate the machine. Initiate the rotation of the drum/wheel. H. Vary the drum/wheel speed while monitoring the speed sensor output signal.	The frequency changes over the full range of the speed sensor.	OK - The sensor signal responds correctly. The sensor is operating correctly. Proceed to Test Step 4. NOT OK -The sensor signal does not respond correctly. The sensor is NOT operating correctly. Repair:Replace the sensor. Proceed to Test Step 5.
4. Check The Operation Of The ECM Note: The disconnect switch and the key start switch remain in the OFF position. The machine harness connector for the speed sensor and the ECM connector remain disconnected. A. Remove the jumper wire that was installed in the last test step. B. At the machine harness connector for the ECM, use a 151-6320 Removal Tool to remove the speed sensor signal wire and socket at contact from the harness connector. C. Reconnect the machine harness connector to the ECM. D. Turn the disconnect switch and the key switch to the ON position. E. Use a 7X-1710 Multimeter Probe that is not connected to a multimeter or a similar device to contact the ECM pin through the vacant space in the ECM harness connector. F. While observing the status of the active diagnostic code, ground the other end of the 7X-1710 Multimeter Probe to frame ground.	The diagnostic code is no longer active.	OK - The diagnostic code is no longer active. The ECM has responded correctly to the grounded circuit condition in the speed sensor circuit. The ECM is most likely not causing the problem. Proceed to Test Step 5. NOT OK - The diagnostic code remains active when the ECM pin for the speed sensor is grounded. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. Proceed to Test Step 5.
5. 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 diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The 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 - The 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 the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

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Table 3
FMI 8 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Verify The Software Version A. Check and record the latest software version for the machine electronic controls from SIS. B. Verify that the latest version of software has been loaded to the ECM.	The software is current.	OK - All of the software is current. Proceed to Test Step 2. NOT OK - There is a more recent software release that is available. Repair: Flash all controls with the latest software release. Refer to Troubleshooting, "ECM Software - Install". Proceed to Test Step 4.
2. Check The Signal Circuit For An Open A. The key start switch and the disconnect switch remain in the OFF position. B. Disconnect the machine harness connector from the sensor. C. Disconnect the machine harness connectors from the ECM. D. At the harness connector for the sensor, place a jumper wire between the signal contact and the return contact. E. At machine harness connector for ECM, measure the resistance between the signal contact the return contact.	The resistance value is less than 5 Ω.	OK - The resistance value is less than 5 Ω. The harness is correct. Proceed to Test Step 3. NOT OK - The resistance is greater than 5K Ω. There is an open circuit in the signal circuit or the return circuit. Note: A resistance greater than 5 Ω but less than 5KΩ indicates a loose connection or corroded connection in the circuit. A resistance value that is greater than 5K Ω would indicate an open in the circuit. Repair: Repair or replace the machine harness. Proceed to Test Step 4.
3. Check The Signal Circuit For A Short A. The disconnect switch and the key start switch remain OFF. B. The sensor and the ECM remain disconnected from the harness. C. Measure the resistance between the signal contact and all other contacts used in the ECM harness connectors.	The resistance values are greater than 5K Ω.	OK - The resistance values are greater than 5K Ω. The harness circuit is correct. The sensor may have failed. Repair- Replace the speed sensor. Proceed to Test Step 4. NOT OK- A resistance value is less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the circuit with the low resistance value. 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 value that is greater than 5K Ω would indicate an open in the circuit. Proceed to Test Step 4.
4. 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 diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The 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 - The 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 the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.