COVER-VALVE MECHANISM 4550954 - Caterpillar

Illustration 1 g03372558
Schematic of the Right Drive Motor Speed Sensors
This diagnostic code is associated with the Right Drive Motor Speed Sensor #1. Each motor has two speed sensors, two signal wires, a power signal wire, and a ground. The ECM is able to diagnose each signal wire independently. Each signal wire provides a frequency input to the ECM that is proportional to motor speed. If this diagnostic code is active, the ECM will keep the code active until a good sensor signal is observed by the ECM. This means that the drive motors must be moved in order for the ECM to determine if the active code can be cleared.This diagnostic code is recorded when the machine ECM receives an incorrect motor speed signal from the speed sensor. The incorrect signal that is being read by the machine ECM has the following characteristics: Abnormal frequency, pulse width, or periodThe possible causes of this diagnostic code are listed:
The supply circuit is open.
The return circuit is open.
The signal circuit is open.
The signal circuit is shorted.
Debris on the sensor.
The sensor has failed.
The ECM has failed. ECM failure is unlikely.Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean. Verify that all connections in the circuit are secure. Verify that all connections in the circuit are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.System Response:CID 2687 FMI 02 will generate a level 2 warning. "Closed Loop Control " and "Unexpected Motor Speed Detection Control" will be disabled. While the machine is moving, a level 3 event will be active indicating that "Unexpected Motor Speed Detection" is disabled E695.Troubleshooting:Note: The following test procedure may create other diagnostic codes. Clear the diagnostic codes when the problem has been corrected. Verify that (CID 2687 FMI 02) is active before performing this procedure.Test Step 1. Check Power At The Sensor
Disconnect the sensor from the machine harness.
Turn the key start switch to the ON position.
At the machine harness for the sensor, measure the voltage. Measure the voltage from contact 1 wire (P769-YL(Yellow)) and contact 2 wire (P770-WH(White)). Expected Result:The voltage that is measured is 8.0 1.0 DCV.Results:
OK - The voltage measurement is 8.0 1.0 DCV. Proceed to test step 2.
NOT OK - The voltage is not correct.Repair: Repair the harness or replace the harness. Verify that the diagnostic has been cleared. Drive the machine above the speed threshold. Verify that the diagnostic tool has been cleared.STOPTest Step 2. Check For An Open Signal Circuit
Disconnect the negative battery cable and turn the key start switch to the OFF position.
Remove the connector from the speed sensor and place a jumper between pins 3 and 4.
Disconnect the J1 and J2 harness connectors from the ECM and then measure the resistance between contacts J2-38 wire