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| Illustration 1 | g01338835 |
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Connections of the transmission output speed sensor 1 | |
This diagnostic code is associated with the transmission output speed sensor 1. The FMI 12 means that the ECM has determined that the signal frequency or the signal pulse width is not within the expected range.
System Response:
A diagnostic code will be displayed on the Caterpillar Electronic Technician (Cat ET). The tractor will operate normally unless more than one speed sensor has failed.
Test Step 1. CHECK THE RESISTANCE OF THE CASE OF THE SENSOR .
- Turn the key start switch and the disconnect switch (if equipped) to the OFF position.
- Disconnect the machine harness connector from the sensor.
- Measure the resistance from contact 1 and from contact 2 to the case of the sensor.
Expected Result:
The resistance is greater than 5,000 ohms.
Results:
- OK - The resistance is greater than 5,000 ohms. Proceed to Test Step 2.
- NOT OK - The resistance is NOT greater than 5,000 ohms. The speed sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 2. CHECK THE RESISTANCE OF THE SENSOR.
- The key start switch and the disconnect switch (if equipped) remain in the OFF position.
- Measure the resistance between contact 1 and contact 2 of the connector of the sensor.
Expected Result:
The resistance is between 600 and 1800 ohms.
Results:
- OK - The resistance is between 600 and 1800 ohms. The resistance is correct. Proceed to Test Step 3.
- NOT OK - The resistance is NOT between 600 and 1800 ohms. The resistance is not correct. The sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 3. CHECK FOR AN OPEN HARNESS.
- The key start switch and the disconnect switch (if equipped) remain in the OFF position.
- Reconnect the machine harness connector to the sensor.
- Disconnect the machine harness connectors J1 and J2 from the machine ECM.
- At the machine harness connector J1, measure the resistance from contact J1-41 to J1-40.
Expected Result:
The resistance is between 600 and 1800 ohms.
Results:
- OK - The resistance is between 600 and 1800 ohms. The circuit is correct. Proceed to Test Step 4.
- NOT OK - The resistance is NOT between 600 and 1800 ohms. The circuit is open in the machine harness.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK FOR A SHORT IN THE RETURN CIRCUIT OF THE MACHINE HARNESS.
- The key start switch and the disconnect switch (if equipped) remain in the OFF position.
- Disconnect the machine harness from the sensor.
- At the machine harness connector J1, measure the resistance between contacts J1-40 and J1-41 to all sources of ground.
Expected Result:
Each resistance measurement is greater than 5000 ohms.
Results:
- OK - Each resistance measurement is greater than 5000 ohms. Proceed to Test Step5.
- NOT OK - There is a short in the machine harness.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 5. INSPECT THE SENSOR AND ADJUST THE SENSOR.
- The key start switch and the disconnect switch (if equipped) remain in the OFF position. The sensor remains disconnected from the machine harness.
- Remove the speed sensor. Inspect the sensor for damage or the presence of foreign material on the tip.
Expected Result:
The sensor is free of foreign material and the sensor is not damaged.
Results:
- OK - The sensor is free of damage. Foreign material is present on the sensor.
Repair: Clean the sensor and reinstall the sensor.
Proceed to Test Step 6.
- NOT OK - The sensor is damaged.
Repair: Replace the speed sensor.
STOP
Test Step 6. CHECK IF THE DIAGNOSTIC 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 191 FMI 12.
Expected Result:
The SPN 191 FMI 12 is active.
Results:
- YES - The SPN 191 FMI 12 is active. The diagnostic code has not been corrected.
Repair: Check the circuit again. If the Caterpillar Electronic Technician (Cat ET) is available, use the Cat ET service tool in order to perform a “Wiggle Test” on the machine wiring harness. The “Wiggle Test” can detect shorts and opens in the machine wiring harness that are momentary or intermittent.
It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - The SPN 191 FMI 12 is not active. The diagnostic code does not exist at this time. The initial diagnostic 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