STUD 2373759 - Caterpillar

The engine's control system must receive an accurate signal that indicates the power output of the generator. When the generator is stopped, the signal must be less than 0.01 VDC. The offset voltage is the voltage level of the signal when the generator is stopped.An offset voltage above 0.01 VDC can be reduced by adding resistance to the circuit.The following steps describe the procedure for adding the correct amount of resistance to the circuit in order to reduce the offset voltage to an acceptable level.Refer to Illustrations 1.
Illustration 1 g02298863
Schematic of the wiring for the load signal
Identify the Configuration of the Wiring.
Remove the electrical power from the engine.
Carefully inspect the wiring between the generator output power sensor and the master Electronic Control Module (ECM). Determine if a potentiometer has been connected to the wiring. A potentiometer must be connected to the wiring in order to perform this procedure. If a potentiometer is installed, proceed to the next Test Step. Otherwise, perform the following procedure in order to install a potentiometer:The potentiometer must have the following characteristics:
5000 Ohms
Linear taper
10 turnsThe wattage rating of the potentiometer is not important. 122-9457 Potentiometer meets these specifications.
Connect the terminal for the wiper to an end terminal. Use a piece of 16 gauge wire in order to make the connection.
Refer to Illustration 1. Connect the potentiometer to the wiring. Use 16 gauge wire in order to make the connections. You may connect the potentiometer to the positive terminal or to the negative terminal of the generator output power sensor.
Adjust the Potentiometer to the Minimum Value.
Disconnect one of the wires that is used to connect the potentiometer to the circuit.
Connect an ohmmeter to the terminals at each end of the potentiometer.
Adjust the potentiometer in order to create the minimum resistance across the terminals.
Reconnect the wire to the circuit.
Adjust the Potentiometer.
Insert 7X-1710 Multimeter Probes into the following terminals of the master ECM:
P1-19
P1-25
Connect a digital voltmeter to the probes. The polarity of the connections is not important.
Restore the electrical power to the engine. Set the engine control to the STOP position.
Verify that the probes are making good contact with the terminals inside the connector. Measure the DC voltage at the terminals.
While you are measuring the voltage at the terminals, slowly adjust the potentiometer. The voltage reading will decrease as you increase the resistance. The adjustment is correct when the voltage reading is between 0.00 VDC and 0.01 VDC. A reading of zero VDC is ideal.
Remove the multimeter and the probes from the connector.
Adjust the "Power Monitoring" parameters. Refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".