TURBO GP - 3355876 - Caterpillar

Illustration 1 g01860879
Schematic of the transmission output speed sensor (No. 2)This diagnostic code is recorded when the ECM receives an incorrect output signal from the transmission output speed sensor (No. 2). The signal is below the dropout signal level. The machine must be moving in order to initially log the diagnostic code for the sensor. The incorrect signal that is being read by the ECM has the following characteristics: erratic, intermittent and incorrect. The ECM determines that this condition exists by comparing the information from the signals. The ECM compares the two signals from the speed sensors. The ECM checks if one of the two signals is invalid or out of the range.The following conditions must be present before the diagnostic code will be active:
The signal from the transmission output speed sensor (No. 2) to the ECM is incorrect.System Response:If the transmission output speed sensor (No. 1) is working properly, this diagnostic code will have no effect on the machine response.Note: The ECM will not sense a signal from the speed sensor unless the machine is moving. When the ECM determines that a signal exists, the diagnostic code is not active.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.
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.STOPTest Step 2. CHECK THE RETURN CIRCUIT.
The disconnect switch and the key start switch remain in the OFF position.
The machine harness remains disconnected from the sensor.
Disconnect machine harness connectors J1 and J2 from the ECM.
Measure the resistance between contact 1 (wire E907-GY) of the machine harness connector for the sensor and contact J2-31 (E907-GY) of the machine harness connector for the ECM.Expected Result:The resistance should measure 5 ohms or less.Results:
OK - The resistance should measure 5 ohms or less. The return circuit is correct. Proceed to test step 3.
NOT OK - The return circuit (wire E907-GY) 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.
Machine harness connectors J1 and J2 remain disconnected from the ECM.
Measure the resistance from the sensor signal J2-25 wire (E906-OR) to the return contact J2-31 wire (E907-GY) of the machine harness.Expected Result:The resistance is less than 5.0 ohms.Results:
OK - The resistance is less than 5.0 ohms. The signal circuit in the machine harness is correct. Proceed to test step 4.
NOT OK - The resistance is greater than 5000 ohms. There is an open in the signal circuit of the machine harness.Repair: Repair the machine harness or replace the machine harness.STOPTest Step