PUMP GP-PISTON 2646027 - Caterpillar

Which Generate This Code:This diagnostic code is associated with the Heading Sensor. The Heading Sensor is an after-market sensor that connects to machines equipped with a Global Positioning System. The sensor communicates with the Machine ECM via the CAN Data Link.The sensor is sending data that is one of the following:
Intermittent
Incorrect
InvalidSystem Response:If the Heading sensor is working incorrectly, the Cat Grade Control system is unable to determine the heading of the machine. The heading value is used to calculate the correct elevations when excavating a design with slope in one or both directions, mainfall, and cross-slope.Test Step 1. CHECK FOR AN OPEN IN THE CAN DATA LINK
Place the key start switch and the disconnect switch in the OFF position.
Disconnect the machine harness connectors "J1" and "J2" from the Machine ECM.
At the harness connectors for the ECM, measure the resistance from contact "J2-45" (wire Y787-YL) to contact "C" of the quick disconnect. Measure the resistance from "J2-46" (wire Y788-GN) to contact "D" of the quick disconnect.Expected Result:Each resistance measurement is 60 ( 5) ohms.Results:
YES - Each resistance measurement is 60 ( 5) ohms. The circuit for the CAN data link is NOT open. Proceed to Test Step 2.
NO - The resistance measurement is greater than 70 ohms. There is an open or a bad connection in the circuit for the CAN data link.Repair: A resistance measurement that is greater than 5000 ohms could indicate that a wire is not connected or that a wire is open. A resistance greater than 70 ohms but less than 5000 ohms indicates a connection point is not open but is not a good connection.Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the circuit for the CAN data link. Ensure that all of the connections are clean, that all of the connections are secure and that all of the connections are in good condition. Repair the machine harness or replace the machine harness.STOPTest Step 2. CHECK THE CAN DATA LINK FOR A SHORT TO GROUND
The key start switch and the disconnect switch remain in the OFF position.
Disconnect the J1 and J2 connectors from the ECM.
Measure the resistance between contact J2-45 (wire Y787-YL) and all pins on the machine harness. Measure the resistance between contact J2-46 (wire Y788-GN) and all pins on the machine harness. Note the resistance.Expected Result:The resistance measurements are greater than 5000 ohms.Results:
YES - Each resistance measurement is greater than 5000 ohms. The CAN data link is not shorted to another circuit in the machine harness.Repair: Contact your technical communicator for a possible consultation with Caterpillar.STOP
NO - One or more of the resistance measurements is less than 5000 ohms. There is a short in the machine harness.Repair: A wire in the circuit for the CAN data link is shorted.Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors in the circuit.For additional information on testing short circuits and locating short circuits, refer to Testing and Adjusting, "Wiring