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| Illustration 1 | g03171003 |
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"Steer Sensor 3" connections | |
Three "steer position sensors" are required for correct operation of the steering control lever. The "steer position sensors" are located in the assembly of the left joystick . Each sensor provides an input signal to the Implement ECM and to the Transmission/Chassis ECM. This diagnostic code is recorded when the ECM reads the signal from the "steer position sensor 3" and the voltage of the signal is below normal.
The "steer position sensor 3" receives power from the 8V power supply of the Transmission/Chassis ECM. The "steer sensor 3" is internally connected to the ground from the 5V sensor return of the Transmission/Chassis ECM and to the Implement ECM (ECM ground). The "steer sensor" must lose the 8V power supply or both grounds in order to lose power. The illustration above indicates the power and ground connections for "steer position sensor 3".
Note: For a schematic of the internal power and ground assignments for each individual component in the left joystick, refer to the Systems Operation, "Features" section of this manual.
The "steer sensor 3" receives power from the 8V power supply of the Transmission/Chassis ECM. The "steer sensor 3" is connected to ground at the 5V sensor return of the Transmission/Chassis ECM (ECM ground) and the 8V sensor return of the Transmission/Chassis ECM(ECM ground). The "steer sensor" must lose the 8V power supply or both grounds in order to lose power. The illustration above indicates the power and ground connections for the "steer sensor 3".
The position sensor is a PWM sensor that operates at a frequency of 500 ± 100 Hz. The position sensor sends a PWM input signal to the Implement ECM and to the Transmission/Chassis ECM. The duty cycle of the signal will vary from approximately 10 ± 5% at the full left position of the joystick to approximately 90 ± 5% at the full right position of the joystick. When the joystick is in the center position, the duty cycle will be approximately 50%.
The possible causes of this diagnostic code are listed below:
- The signal circuit is shorted to a ground source.
- The sensor has failed.
- The ECM has failed. This is unlikely.
Note: Before performing this procedure, check for an active MID 027 CID 0041 diagnostic code for the 8V sensor power supply of the Transmission/Chassis ECM. Correct any problem with the 8V power supply before performing this procedure.
Note: The Transmission/Chassis ECM (MID 027) and the Implement ECM (MID 082) receive an input signal from the "steer sensor 3". Both ECM modules can activate a CID 1473 FMI 04 diagnostic code when the signal voltage is below normal. If one ECM has activated a CID 1473 FMI 04 diagnostic code and the other ECM has not, it is likely that the sensor is operating correctly. When this occurs, a poor connection in the machine harness would be suspected. When both ECM modules have activated the diagnostic code, either the sensor OR a harness problem could be the cause. If both ECM modules have activated the diagnostic code, it is very unlikely that either ECM is causing the problem. For either condition, proceed with this procedure in order to verify the cause of the problem.
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, that all connections are secure and that all connections are 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 SENSOR
- Turn the disconnect switch and the key start switch to the ON position.
- Disconnect the machine harness connector J3 from the left joystick. Observe the status of the active CID 1473 FMI 04 diagnostic code.
Expected Result:
The status of the CID 1473 FMI 04 diagnostic code did not change when the connector of the joystick was disconnected. A CID 1473 FMI 03 diagnostic code has NOT been activated by either the Implement ECM or the Transmission/Chassis ECM. The CID 1473 FMI 04 diagnostic code remains active when the connector of the joystick is disconnected.
Results:
- YES - The CID 1473 FMI 04 diagnostic code remains active when the connector of the joystick is disconnected. The sensor is not causing the problem. Proceed to Test Step 2.
- NOT OK. - The CID 1473 FMI 04 diagnostic code is no longer active when the connector of the joystick is disconnected. A CID 1473 FMI 03 diagnostic code has been activated by both of the ECM modules when the connector of the joystick is disconnected. The machine harness and the ECM are operating correctly.
Repair: The "steer sensor 3" is causing the problem. There is an internal short to ground in the left joystick. Replace the assembly of the left joystick. After replacement of the assembly of the joystick, verify that the operation of the new assembly of the joystick is correct before operating the machine.
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Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND
- The connector of the joystick J3 remains disconnected from the machine harness.
- Turn the key start switch and the disconnect switch to the OFF position.
- Disconnect the J1 and J2 machine harness connectors from the Implement ECM.
- Disconnect the J1 and the J2 connectors from the Transmission/Chassis ECM.
- At machine harness connector J2 for the Implement ECM, measure the resistance from contact J2-34 (wire U741-OR(Orange)) to frame ground. Measure the resistance from contact J2-34 (wire U741-OR(Orange)) to all of the other J1 and J2 contacts that are used for the Implement ECM.
- At the J2 machine harness connector for the Transmission/Chassis ECM, measure the resistance from the sensor signal contact J2-34 (wire U741-OR(Orange)) to frame ground and measure the resistance to all of the other J1 and J2 contacts that are used for the Transmission/Chassis ECM.
Expected Result:
Each resistance measurement is greater than 5kΩ.
Results:
- OK. - Each resistance measurement is greater than 5kΩ. The resistance checks of the signal circuit do not indicate a short in the machine harness. Proceed to Test Step 3.
- NOT OK. - One or more of the resistance measurements is less than 5kΩ.
Repair: There is a short in the machine harness. The short is between the signal circuit and either the frame ground or the circuit with the low resistance measurement.
Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the sensor circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition.
For information on testing for short circuits and finding short circuits, refer to Testing and Adjusting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.
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Test Step 3. 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 is 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 sensor circuit. - Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are completely fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Determine if the CID 1473 FMI 04 diagnostic code is active.
Expected Result:
The CID 1473 FMI 04 diagnostic code is not active.
Results:
- OK. - The CID 1473 FMI 04 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 operation.
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- NOT OK. - The CID 1473 FMI 04 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.
If both the Transmission/Chassis ECM and the Implement ECM have activated this diagnostic code, it is very unlikely that either ECM is causing the problem.
Exit this procedure and perform this procedure again. If the cause of the failure is not found, contact the Technical Communicator of your dealership 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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