TUBE 3C8349 - Caterpillar

Illustration 1 g01185056
Schematic of the Speed Sensor (Engine)
This diagnostic code is recorded when the ECM reads the signal from the sensor and the ECM determines that the signal is erratic, intermittent or incorrect. One of the following conditions must be present before the diagnostic code will be active:
The signal from the engine speed sensor to the transmission ECM is incorrect.
The transmission ECM is NOT receiving the correct information about the engine 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 12. Correct the related CID 0248 FMI 12 first. Then view the status of the other diagnostic codes and correct the other active codes.Test Step 1. CHECK THE RESISTANCE OF THE SENSOR.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the speed sensor.
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 110 ohms and 200 ohms.Results:
OK - The resistance measurement is between 110 ohms and 200 ohms. The speed sensor has not failed. Proceed to Test Step 2.
NOT OK - The speed sensor has failed.Repair: The speed sensor has failed. Replace the sensor. Refer to the service manual of the engine in order to ensure that the speed sensor is properly installed and that the speed sensor is properly adjusted. Verify that the new sensor corrects the problem.STOPTest Step 2. CHECK THE RETURN CIRCUIT.
The machine harness remains disconnected from the sensor.
Turn the key start switch to the OFF position.
At the machine harness connector for the sensor, measure the resistance between contact 1 (L913-OR(Orange)) and frame ground. Expected Result:The resistance should measure 20 ohms or less.Results:
OK - The resistance measures 20 ohms or less. The return circuit is correct. Proceed to Test Step 3.
NOT OK - The resistance does not measure 20 ohms or less.Repair: The return circuit (L913-OR(Orange)) in the machine harness has excessive resistance (open). Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK THE SIGNAL CIRCUIT FOR AN OPEN IN THE MACHINE HARNESS.
At the machine harness connector for the speed sensor, place a jumper between the two contacts.
Disconnect the machine harness connectors J1 and J2 from the ECM.
At the machine harness connectors J1 and J2, measure the resistance from J1-24 (sensor signal) to J1-3 (the return circuit). Expected Result:There should be less than 5.0 ohms resistance. Results:
OK - There is less than 5.0 ohms resistance. The signal circuit in the machine harness is correct. Proceed to Test Step 4.
NOT OK - There is not less than 5.0 ohms resistance.Repair: The signal circuit (L912-WH(White)) is open in the machine harness. Repair the machine harness or replace the machine harness.STOPTest Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT.
If a jumper was used in a previous step, remove the jumper.
Reconnect the machine harness to the speed sensor.
At the harness connector J1