PUMP GP-PISTON 2074709 - Caterpillar

Illustration 1 g00600204
Schematic of the Engine Speed SensorThis diagnostic code is for the engine speed sensor.This diagnostic code is recorded when the ECM reads the signal from the engine speed sensor and the ECM determines that the signal is erratic, intermittent or incorrect. This is determined when the ECM compares the signal from the engine speed sensor to the signal from the torque converter output speed sensor. A diagnostic code is recorded when the signal from the engine speed sensor is below the dropout value and the engine speed is above low idle. This problem prevents the ECM from calculating the ratio of the torque converter. Note: The engine must be running. The engine speed signal must be received from the torque converter output speed sensor in order for the ECM to display this diagnostic code as being present. Test Step 1. CHECK THE RESISTANCE OF THE SENSOR.
Turn the key start switch to the OFF position.
Disconnect the machine harness from the speed sensor.
Measure the resistance between the two contacts of the connector for the speed sensor. Expected Result:The resistance measurement should be 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 resistance measurement is not between 110 ohms and 200 ohms.Repair: The speed sensor has failed. Replace the sensor. Adjust the speed sensor properly when the sensor is being installed. See Testing and Adjusting, "Speed Sensor - Adjust". Verify that the new sensor corrects the problem. Stop.Test 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 (G939-PK) 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 (G939-PK) in the machine harness has excessive resistance (open). Repair the machine harness or replace the machine harness. Stop.Test 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 J2-38 (sensor signal) to J1-15 (the return circuit) and to J1-16 (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 (450-YL) is open in the machine harness. Repair the machine harness or replace the machine harness. Stop.Test Step 4. CHECK THE SIGNAL CIRCUIT