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| Illustration 1 | g01527008 |
Schematic of the position sensor for the retarder | |
This diagnostic trouble code is associated with the position sensor for the retarder. The FMI 8 means that the ECU has determined that the signal frequency or the signal pulse width is not within the expected range.
The position sensor is a PWM sensor that has a frequency of 500 hertz. The duty cycle operates from a range of 10% to 90%. As the lever is moved downward the duty cycle increases.
The possible causes of this diagnostic code are listed below:
- The sensor has failed.
- Intermittent connections or poor connections
- Mechanical devices are loose.
- The ECU has failed. This is unlikely.
Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear the diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of SPN 1716 FMI 8 is active before performing this procedure.
Note: Use a digital multimeter for the measurements in this procedure.
Test Step 1. CHECK FOR POWER AT THE SENSOR.
- Do not disconnect the harness connector from the sensor.
- At the back of the harness connector for the sensor, use an electrical spoon in order to insert a multimeter probe along the voltage supply wire (contact A).
- Turn the key start switch and the disconnect switch to the ON position.
- Measure the voltage from contact A to frame ground.
Expected Result:
The voltage is 24 DCV.
Results:
- OK - The voltage is 24 DCV. Proceed to Test Step 2.
- NOT OK - The voltage is not 24 DCV. The circuit is open.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 2. CHECK THE SIGNAL CIRCUIT OF THE SENSOR.
- Turn the key start switch and the disconnect switch to the OFF position.
- At the back of the harness connector for the sensor, remove the multimeter probe from contact A and insert the probe with the electrical spoon along the signal wire (contact C).
- At the back of the harness connector for the sensor, use an electrical spoon in order to insert the multimeter probe along the ground wire (contact B).
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with the digital multimeter.
- Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range of the sensor.
Note: On some machines, it may be necessary to start the engine in order to take the sensor through the full operating range of the sensor. Push the pedal in order to see a change.
Expected Result:
The sensor's signal responds in the manner that is described at the begining of this procedure.
Results:
- OK - The sensor's signal responds correctly. The sensor is operating correctly. Proceed to Test Step 3.
- NOT OK - The sensor's signal does not respond correctly. The sensor is NOT operating correctly.
Repair: Replace the sensor.
STOP
Test Step 3. CHECK THE SIGNAL CIRCUIT AT THE ECU.
- Turn the key start switch and the disconnect switch to the OFF position.
- Use an electrical spoon in order to insert the multimeter probe into the back of the connector for the ECU along J2-42 (wire Y924-OR).
- Connect the other multimeter probe to a clean source of frame ground.
- Turn the disconnect switch and the key start switch to the ON position.
- Monitor the signal of the sensor with the digital multimeter.
- Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range of the sensor.
Note: On some machines, it may be necessary to start the engine in order to take the sensor through the full operating range of the sensor. Push the pedal in order to see a change.
Expected Result:
The sensor's signal responds in the manner that is described at the begining of this procedure.
Results:
- OK - The sensor's signal responds correctly. The sensor is operating correctly. Proceed to Test Step 4.
- NOT OK - The sensor's signal does not respond correctly. The harness has failed.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT IN THE HARNESS.
- The key start switch and the disconnect switch remain in the OFF position.
- Disconnect the machine harness connectors from the sensor and the ECU.
- Measure the resistance between contact J2-42 (wire Y924-OR) and all contacts that are used in the machine harness connectors for the ECU.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 5.
- NOT OK - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 5. CHECK IF THE DIAGNOSTIC TROUBLE CODE REMAINS
- Inspect the harness connectors. Clean the contacts of the harness connectors and 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 circuit.
- Reconnect all harness connectors. Make sure that the harness connectors are fully seated and that the clips for each connector are completely fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the vehicle.
- Check the status of the SPN 1716 FMI 8.
Expected Result:
The SPN 1716 FMI 8 is active.
Results:
- YES - The SPN 1716 FMI 8 is active. The diagnostic trouble code has not been corrected.
Repair: Check the circuit again. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. Prior to replacing an ECU, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".
STOP
- NO - The SPN 1716 FMI 8 is not active. The diagnostic trouble code does not exist at this time. The initial diagnostic trouble code was probably caused by a poor electrical connection at one of the harness connectors that was disconnected and reconnected. Resume normal vehicle operation.STOP