The Bus Transformer Box (BTB +) reduces the AC line to neutral voltages of phase A and phase C from the bus to usable signal levels for the GSC+P. The GSC+P uses these reduced signals for detecting the phase angle with the generator. The GSC+P also uses these reduced signals for detecting the phase sequence of the bus. The GSC+P will utilize the signal of phase A in order to measure the amplitude of the voltage on the bus. The GSC+P will utilize the signal of phase C in order to measure the frequency of the voltage on the bus.
The possible cause of a CID 1170 FMI 02 is a short between the input of phase A and the input of phase B of the BTB+. This would cause a phase angle of approximately 0°.
Test Step 1. CHECK THE PHASE ANGLE OF THE INPUTS TO THE BUS TRANSFORMER BOX (BTB +)
- Stop the engine. Turn the Engine Control Switch (ECS) to "STOP".
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| Illustration 1 | g00603288 |
Bus transformer box | |
- 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 INPUT OF THE BTB+
- Start the engine and run the engine at rated speed.
- The Bus must be live. Close the breaker of the generator.
- Use a digital multimeter and measure the voltage between "B1" and "B2" on the BTB+.
Expected Result:
The voltage between "B1" and "B2" of the generator is the same as the 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 ECS to "STOP". Ensure that no other source is connected to the bus.
- Disconnect the wires labelled "E486" and "E488" from the BTB+ terminals.
- Measure the resistance between "E486" and "E488" and 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. Refer to 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+. Refer to 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 pins 17 and 18 of the 40-pin connector.
- Start the engine. The engine is running at rated speed.
- Measure the voltage between pin 17 and pin 18 of the GSC+P connector.
Expected Result:
The voltage should be equal to the voltage measured in Test Step 2 divided by 15 ± 2% (14.7 to 15.3).
Results:
- OK - The voltage is correct. CID 1170 FMI 2 is still active. The GSC+P may have failed.
Repair: It is unlikely that the GSC+P has failed. Exit this procedure and perform this entire procedure again. If the result is the same, replace the GSC+P. Refer to Testing and Adjusting, "EMCP Electronic Control (Generator Set) - Replace".
STOP
- NOT OK - The voltage is not correct. Proceed to Test Step 5.
Test Step 5. CHECK VOLTAGE ON BTB+ OUTPUT
- Stop the engine.
- Install cable probes between pin A and pin B of three terminal connector "J1" on the BTB+.
- Start the engine and run the engine at rated speed.
- Measure the voltage between pin A and pin B of "J1".
Expected Result:
The voltage should be equal to the voltage measured in Test Step 2 divided by 15 ± 2% (14.7 to 15.3).
Results:
- OK - The voltage is correct. There is a wiring failure between the GSC+P and the BTB+.
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. Testing And Adjusting, "Schematics And Wiring Diagrams".
STOP
- NOT OK - The voltage is not correct. Proceed to Test Step 6.
Test Step 6. CHECK THE BTB+ OUTPUT CIRCUIT
- Stop the engine.
- Disconnect three terminal connector J1 on the BTB+.
- Measure the resistance from pin A to pin B of J1.
Expected Result:
The resistance should be 14.6 ohms ± 3.0 ohms.
Results:
- OK - The resistance is correct. There may be an intermittent problem.
Repair: The system may need to be reset. Shut down the system by turning the ECS to the OFF/RESET position. Then, restart the genset and verify that the genset is operating properly. Watch the genset for any recurrence of the problem.
STOP
- NOT OK - The resistance is not correct. The BTB+ is faulty.
Repair: The BTB+ has failed. Replace the BTB+. Refer to Testing and Adjusting, "EMCP Electronic Control (Bus Transformer Box) - Replace"
STOP