PLUNGER ASSEM. 6L4888 - Caterpillar

Illustration 1 g02729262
Schematic of the speed sensor for the engine
This diagnostic code applies to the engine speed sensor.This diagnostic code is recorded when the Brake ECM reads the signal from the speed sensor of the engine and the Brake ECM determines that the signal is erratic, intermittent, or incorrect. 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.Note: The machine must be moving 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 900 ohms and 1300 ohms. Results:
OK - The resistance measurement is between 60 ohms and 250 ohms. The speed sensor has not failed. Proceed to Test Step 2.
NOT OK - The resistance measurement is not between 60 ohms and 250 ohms.Repair: The speed sensor has failed. Replace the sensor. 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 (451-BR(Brown)) 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 (451-BR(Brown)) 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 wire 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 J1-2 (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 (451-BR(Brown)) 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 and harness connector J2, measure the resistance between J1-2 (450-YL(Yellow)) and all sources of positive voltage and ground. Expected Result:Each resistance should be greater than 5000 ohms. Results:
OK - Each resistance is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 5.
NOT OK - Each resistance is not greater than 5000 ohms.Repair: