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| Illustration 1 | g02297773 |
Steering sensor circuit | |
Three steer position sensors are required for correct operation of the steering control. The steer position sensors are located in the left joystick. Each sensor provides an input signal to the Machine ECM that will indicate the position of the steering control handle.
The FMI 12 means that the ECM has determined that the signal frequency of the Steer Position Sensor 2 is not within the expected range.
The Steer Position Sensor 2 receives power from the Machine ECM 8 V power supply circuit and the 8 V return circuit.
The position sensor is a PWM sensor that operates at a frequency of approximately 500 Hz. The position sensor sends a PWM input signal to the Machine ECM. The duty cycle of the signal will vary from approximately 10 percent when the steering control handle is at the full left position to approximately 90 percent when the steering control handle is at the full right position. When the steering control handle is at the center position, the duty cycle will be approximately 50%.
The possible causes of this diagnostic code are listed below:
- The sensor has failed.
- The ECM has failed. ECM failure is unlikely.
This procedure should not require entry into any enclosures that contain hazardous voltage components and should not require any hazardous voltage connections to be disconnected.
When an area that contains hazardous voltage components must be entered for a service procedure, the "Safe Shutdown Procedure for Electric Drive Tractors" procedure must be performed before any enclosures that contain hazardous voltage components are opened or before any hazardous voltage connectors are disconnected. Refer to the Troubleshooting, "Electrical Maintenance Guidelines" section of this manual. Perform the "Safe Shutdown Procedure for Electric Drive Tractors" procedure before any of the hazardous voltage areas are opened or before hazardous voltage connectors are disconnected.
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.
Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.
Test Step 1. CHECK THE DUTY CYCLE AND THE SIGNAL FREQUENCY AT THE SENSOR
Turn the key start switch and the disconnect switch to the OFF position. Follow the safe power down procedure that is detailed at the beginning of this procedure.
- At the machine harness side of the steering control connector, use a 151-6320 Removal Tool to remove signal wire U740-BR and socket at J1-7 from the harness connector. The machine harness connector remains connected to the steering control handle connector.
- At the vacant space in the machine harness connector where the signal wire was removed, use the positive side 7X-1710 Multimeter Probe to insert into connector J1-7 to contact the signal pin on the steering control handle connector. Insert the other probe along the sensor return J1-8 (wire P967-PU). Ensure that a good contact is made between the probes and the sensor contacts.
- Turn the disconnect switch and the key start switch to the ON position. DO NOT START THE ENGINE.
- With the Speed / Direction Handle in the center position and stationary, measure the frequency of the signal from the sensor.
- While observing the measurement, wiggle the steering control connector. Gently pull on the wires and move the wires around.
- With the left joystick in the center position and stationary, measure the duty cycle of the sensor at the steering control connector J1-7 and J1-8.
- While observing the duty cycle measurement, wiggle the joystick connector. Gently pull on the wires and move the wires around.
Expected Result:
The frequency of the steer sensor 2 signal is 500 ± 80 Hz. The duty cycle of the steer sensor 2 is approximately 50 percent. The frequency and the duty cycle are stable during the manipulation of the harness connector and the wiring.
Results:
- OK - The signal frequency and the duty cycle of the sensor is correct and did not change when the harness is manipulated. The sensor is not causing the problem.
Reconnect the signal wire and socket in the machine harness connector for the handle. Verify that all of the circuit wires are secure in the steer handle connector before proceeding to the next step.
Proceed to Test Step 2. - NOT OK - The signal frequency is less than 400 Hz and the duty cycle of the steer sensor 2 is NOT correct according to the description at the beginning of this procedure. The sensor has failed.
Repair: Perform this test step again in order to verify that the sensor signal is not correct.If the steer sensor 2 signal is not correct according to the description at the beginning of this procedure, replace the Speed / Direction Handle assembly. After replacement of the handle assembly, verify that the operation of the new steering control handle is correct before operating the machine.
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Test Step 2. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that can be caused by excessive heat, battery acid, or chafing.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.
- Reconnect all harness connectors making sure that the connectors are fully seated and the clips for each connector are fastened.
- Turn the disconnect switch and the key start switch to the ON position. DO NOT START THE ENGINE.
- Check the status of the CID 1472 FMI 12 diagnostic code.
Expected Result:
The CID 1472 FMI 12 diagnostic code is not active.
Results:
- OK - The CID 1472 FMI 12 diagnostic code is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operationSTOP
- NOT OK - The CID 1472 FMI 12 diagnostic code is active. The diagnostic code has not been corrected.
Repair: Check the circuit again. Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a "Wiggle Test" on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness.If the cause of the active diagnostic code is not found, the ECM that has activated this diagnostic code may have failed. Exit this procedure and perform this procedure again. If the cause of the failure is not found, contact your dealership Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
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