FILM 3C8491 - Caterpillar

Illustration 1 g01192908
Schematic of the Speed Sensor (Torque Converter Output) This diagnostic code is recorded when the ECM receives an incorrect signal from the torque converter speed sensor. The signal is below the dropout signal level. The engine must be running. The incorrect signal that is being read by the ECM has the following characteristics: erratic, intermittent and incorrect. One of the following conditions must be present before the diagnostic code will be active:
The signal from the speed sensor to the ECM is incorrect.
The ECM is NOT receiving the correct information about the speed sensor over the data link.Note: Check for other related diagnostic codes before performing the following diagnostic code procedure. Check for an active CID 0248 FMI 09. Correct the related CID 0248 FMI 09 first. Then view the status of the other diagnostic codes and correct the other active codes.Test Step 1. CHECK THE SENSOR RESISTANCE.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the speed sensor for the torque converter.
At the connector for the speed sensor, measure the resistance between the two contacts of the connector of the speed sensor.Expected Result:The resistance measurement is between 1000 ohms and 1200 ohms. Results:
OK - The speed sensor has not failed. Proceed to test step 2.
NOT OK - The speed sensor has failed.Repair: Replace the sensor. Adjust the speed sensor properly during the installation. See Testing and Adjusting, "Speed Sensor (Transmission Output) - Replace".STOPTest Step 2. CHECK THE RETURN CIRCUIT.
The machine harness remains disconnected from the sensor.
The disconnect switch and the key start switch remain in the OFF position.
At the machine harness connector for the sensor, measure the resistance between contact J1-5 (wire L911-WH) and frame ground.Expected Result:The resistance should measure 5 ohms or less.Results:
OK - The return circuit is correct. Proceed to test step 3.
NOT OK - The return circuit (wire L911-WH) in the machine harness has excessive resistance (open).Repair: Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE SIGNAL CIRCUIT FOR AN OPEN IN THE MACHINE HARNESS.
Place a jumper between the two contacts of the machine harness connector for the speed sensor.
Disconnect connectors J1 and J2 from the machine harness of the ECM .
Measure the resistance from the sensor signal J1-4 wire (L910-PK) to the return contact J1-5 wire (L911-WH) of the machine harness.Expected Result:There should be continuity (less than 5.0 ohms resistance). Results:
OK - The signal circuit in the machine harness is correct. Proceed to test step 4.
NOT OK - There is an open in the signal circuit of the machine harness.Repair: Repair the machine harness or replace the machine harness.STOPTest Step 4. CHECK THE SIGNAL FOR A SHORT.
Remove the jumper between the two contacts of the speed sensor of the previous test "CHECK SIGNAL CIRCUIT FOR AN OPEN IN THE MACHINE HARNESS".
Reconnect the machine harness to the speed sensor.
At the J1 and J2 harness connectors, measure the resistance between J1-4 (wire L910-PK) and all sources of positive voltage and ground.Expected Result:Each