CONTROL GP-DIFFERENTIAL LOCK 8W1973 - Caterpillar

Illustration 1 g00603288
Bus transformer box
Stop the engine. Turn the engine control switch (ECS) to "STOP".
Remove the two fuses from the BTB +.
Measure the resistance of the fuses with a digital multimeter.Expected Result:The resistance should be less than 1.0 ohms.Results:
OK - The resistance is less than 1.0 ohms. The fuses have not failed. Install the fuses. Proceed to Test Step 2.
NOT OK - The fuses are blown. Replace the fuses. Proceed to Test Step 2.Test Step 2. CHECK THE VOLTAGE ON THE BTB+ INPUT
Start the engine and run the engine at rated speed.
The Bus must be live. Close the breaker of the generator or energize the Bus from another source.
Use a digital multimeter and measure the voltage between "B1" and "B2" on the BTB+.Expected Result:The voltage should be the same as the rated generator line to line voltage.Note: If external potential transformers for medium and high voltage generators are present, the voltage will be the same as the secondary of the potential transformer.Results:
OK - The voltage is correct. Proceed to Test Step 4.
NOT OK - The voltage is not correct. Proceed to Test Step 3.Test Step 3. CHECK THE BTB+ INPUT CIRCUIT
Stop the engine. Turn the engine control switch (ECS) to "STOP".
Disconnect the wires labelled "B1" and "B2" from the BTB + terminals.
Measure the resistance between "B1" and "B2" on the BTB+.Expected Result:The resistance should be 2140 ohms 400 ohms.Results:
OK - The resistance is correct. There is a failure in the wiring between the BTB+ and the generator. Repair: Use the System Schematic for the BTB+ and the AC schematic in order to troubleshoot the wiring and find the exact cause of the diagnostic code. See Testing And Adjusting, "Schematics And Wiring Diagrams". Stop.
NOT OK - The resistance is not correct. BTB+ has failed.Repair: The BTB+ has failed. Replace the BTB+. See Testing And Adjusting, "EMCP Electronic Control (Bus Transformer Box) - Replace". Stop.Test Step 4. CHECK VOLTAGE ON GSC+P INPUT
Stop the engine.
Install cable probes on the GSC+P 40 pin connector contacts 17 and 18.
Start the engine. The engine is running at rated speed.
Measure the voltage between GSC+P connector contact 17 and 18Expected Result:The voltage should be equal