HEAD-CYLINDER 4894093 - Caterpillar

J2, measure the resistance between the solenoid energize circuit contact J2-5 (wire G731-GY) and the return circuit contact J2-8 (wire M739-YL).
At the Service Brake Pedal Switch, disconnect the solenoid energize wire G731-GY from the normally open switch contact.
Measure the resistance between the disconnected solenoid energize wire G731-GY at the switch and the ECM solenoid return contact J2-8 (wire M739-YL).Expected Result:The resistance measurements should be approximately the same. Each measurement should indicate the resistance of the circuits and the resistance of the solenoid coil. The resistance of a good Service Brake Dump Solenoid coil is approximately 42 ohms at approximately 25 °C (77 °F). Resistance will increase as the temperatures increase.Results:
OK - Both of the resistance measurements are correct. Each of the resistance measurements is approximately the same resistance of the solenoid coil. The solenoid circuits and the solenoid coil are not open. Proceed to Test Step 3.
NOT OK - One or both of the resistance measurements are not correct. The measurement is much less that the resistance of the solenoid coil. There is an open or possibly a poor connection in either one of the solenoid circuits or the solenoid coil is open.Repair: A resistance measurement that is much greater than 5 ohms but less than 5000 ohms could indicate that one of the connection points in the circuit is not open but is not a good connection.Use the results of the resistance measurements to determine which part of the circuit is open.If both of the resistance measurements are not correct, disconnect the solenoid from the machine harness and check the resistance of the solenoid coil. This will indicate whether the solenoid has failed. If the solenoid checks OK, check the continuity of the circuit wires individually in order to detect the open.If the resistance measurement at the ECM connector is correct and the resistance measurement between the switch circuit and the return circuit is not OK, the open is in the switch energize section of the G731-GY wire.If the resistance measurement at the ECM connector is not correct and the resistance measurement between the switch circuit and the return circuit is OK, the open is in the ECM energize section of the G731-GY wire.In order to further isolate the location of the problem in the circuit that passes through the cab wall, check the involved circuits at the 70 pin bulk head connector that is located on the outside of the cab on the lower right side. The lower of the two 70 pin bulkhead connectors pass the majority of Machine ECM circuits through the cab frame to the ECM. Refer to the Troubleshooting, "General Information" section of this manual for a contact assignment illustration for the two 70 pin bulkhead connectors.Perform the procedure to check the suspect circuit for an open at the correct contacts on the 70 pin bulkhead connector.With the jumper wire still in place at the machine harness connector for the component, check the resistance of the circuits at the frame side of