C27 Petroleum Generator Set Engines Caterpillar

Use this procedure in order to troubleshoot the electrical system if a problem is suspected with the throttle signal. Also, use this procedure if the diagnostic code in Table 1 is active or easily repeated.

The direct fuel control mode enables the engine to be controlled by an external governor. A signal converter must be installed on the engine in order to operate in direct fuel control mode. Ensure that the "Direct Fuel Control Mode" configuration parameter is programmed to "Enabled". The ECM will then be configured for a control strategy that supports the direct fuel control mode.

The input to the signal converter must be a 0 to 200 mA signal. The signal is received from the external governor. The output signal from the signal converter is a Pulse Width Modulated signal (PWM) that is sent to the ECM.

The output signal varies with the current to the signal converter. The ECM calculates the desired fuel from this PWM signal.

The duty cycle for a valid signal is between 5 and 95 percent. If an invalid signal is received, the engine will automatically be set to a minimum fuel setting and the engine will shut down.

The following ECM control strategies are not used in direct fuel control mode.

• Low idle speed

• Crank terminate speed

• Cooldown speed

Illustration 1	g02212773
Typical example Schematic for the direct fuel control mode

Illustration 2	g02217154
Terminal locations at the P1 ECM connector (P1-5) Return (P1-66) Throttle signal

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the Engine Control Switch (ECS) to the OFF position. Turn the battery disconnect switch to the OFF position.

2. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

4. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and the wiring for abrasion and for pinch points.

Expected Result:

All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.

Results:

• OK - The connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - The connectors and/or wiring are not OK.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 2. Check the Current Input to the Signal Converter

1. Turn the Engine Control Switch (ECS) to the STOP position. Turn the battery disconnect switch to the ON position.

2. Measure the current to the signal converter.

   Note: Some external governors may only be able to output approximately 150 mA.

Expected Result:

The current range is between 0 and 200 mA.

Results:

• OK - The current is within the correct range. Proceed to Test Step 3.

• Not OK - The current is not within the correct range.

  Repair: Replace the external governor that is supplying the controlling current.

  STOP

Test Step 3. Load Test the Batteries

1. Turn the Engine Control Switch (ECS) to the OFF position. Turn the battery disconnect switch to the OFF position.

2. Measure no-load battery voltage at the battery terminals. Refer to Systems Operation/Testing and Adjusting for details.

3. Load test the batteries.

   ReferenceOperating Manual, SEHS9249

   ReferenceSpecial Instruction, SEHS7633

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 4.

• Not OK - The voltage is not 24 ± 3 VDC.

  Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Verify that the original condition is resolved. Refer to Systems Operation/Testing and Adjusting, "Electrical System".

  STOP

Test Step 4. Check the Battery Voltage at the Signal Converter

1. Turn the Engine Control Switch (ECS) to the OFF position. Turn the battery disconnect switch to the ON position.

2. Check the voltage across the power terminals at the signal converter.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

• OK - The voltage is 24 ± 3 VDC. Proceed to Test Step 5.

• Not OK - The voltage is not 24 ± 3 VDC.

  Repair: Check the wiring and/or the connectors that are between the battery and the signal converter. Repair the wiring and/or connectors.

  STOP

Test Step 5. Use Caterpillar Electronic Technician (ET) to Check the Throttle Position

1. Connect Cat ET to the service tool connector.

2. Turn the Engine Control Switch (ECS) to the STOP position. Turn the battery disconnect switch to the ON position.

3. Observe the throttle position reading on Cat ET.

4. Vary the current to the signal converter.

Expected Result:

The throttle position on Cat ET varies from 0 percent to 100 percent as the current input is adjusted from 0 mA to 200 mA.

Results:

• OK - The throttle position on Cat ET corresponds with the current input.

  Repair: Check the ECM for active diagnostic codes. If no codes are active, there may be an intermittent electrical problem. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

  STOP

• Not OK - The throttle position does not correspond to the current input. Proceed to Test Step 6.

Test Step 6. Check the Signal from the Signal Converter

1. Turn the Engine Control Switch (ECS) to the OFF position. Turn the battery disconnect switch to the OFF position.

2. Remove the signal wire from the signal converter.

3. Turn the Engine Control Switch (ECS) to the STOP position. Turn the battery disconnect switch to the ON position.

4. Set the multimeter to "VDC".

5. Use a multimeter to monitor the output of the percent duty cycle from the signal converter.

6. Adjust the current input from a low current setting to a high current setting.

   Note: The throttle position on Cat ET will not match the percent duty cycle on the multimeter.

7. Restore the wiring to the original configuration.

Expected Result:

The duty cycle is between 5 percent at the low setting and 95 percent at the high setting.

Results:

• OK - The correct signal is being supplied. Proceed to Test Step 7.

• Not OK - The duty cycle is not correct on the multimeter.

  Repair: Replace the signal converter.

  STOP

Test Step 7. Check the Signal at the ECM

1. Turn the Engine Control Switch (ECS) to the OFF position. Turn the battery disconnect switch to the OFF position.

2. Remove wires from P1-66 and P1-5.

3. ECS STOP, battery disconnect switch ON.

4. Use a multimeter to monitor the output of the percent duty cycle from the signal converter.

5. Adjust the current input from a low current setting to a high current setting.

6. Restore the wiring to the original configuration.

Expected Result:

The duty cycle is between 5 percent at the low setting and above 95 percent at the high setting.

Results:

• OK - The duty cycle is correct.

  Repair: There appears to be a problem with the ECM. Before you consider replacing the ECM, consult the Dealer Solutions Network (DSN). Refer to Troubleshooting, "ECM - Replace".

  STOP

• Not OK - The duty cycle is not correct.

  Repair: There is a problem in the wiring between the ECM connector and the signal converter. Repair the wiring or replace the wiring.

  STOP