C175-16 Locomotive Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the fuel control valve or if a diagnostic code in Table 1 is active.

Table 1

Diagnostic Codes Table
Description	Conditions which Generate this Code	System Response
18-8 Fuel Control Valve : Abnormal Frequency, Pulse Width, or Period	The controller for the fuel control valve has detected an error at the input for the Pulse Width Modulated signal (PWM signal). The problem is communicated to the Electronic Control Module (ECM) via the CAN data link.	Control for the fuel control valve reverts to the CAN data link.
18-9 Fuel Control Valve : Abnormal Update Rate	The engine ECM did not receive the expected data link information from the controller for the fuel control valve.	The fuel control valve utilizes the PWM signal for fuel control.
91-8 Throttle Position Sensor abnormal frequency, pulse width, or period	The Electronic Control Module (ECM) detects an incorrect frequency on the throttle signal or an incorrect duty cycle on the throttle signal. The frequency is below 150 Hz or the frequency in above 1000 Hz. The duty cycle is less than 5 percent or the duty cycle is greater than 95 percent. This code is used when the parameter for the "Desired Speed Input Configuration" is configured to "PWM".	The code is logged. The ECM flags the throttle position as invalid data and a default value of zero percent is used. The engine speed is limited to high idle.
1028-6 Power Supply Control 1 : Current Above Normal	The ECM output which powers the Fuel Control Valve has detected a short to ground in the wiring or an internal fault with the fuel control valve.	Engine will be unable to build rail pressure

This engine is equipped with a high pressure common rail fuel system. The fuel pressure for the high pressure common rail fuel system is generated by the high-pressure fuel pump. Pressure regulation for the high-pressure fuel pump is provided by the fuel control valve. The fuel control valve is a mechanical valve that is part of the high-pressure fuel pump. The valve regulates the fuel pressure that is produced by the pump by controlling the volume of fuel that enters the pump. The valve is controlled by an electrical actuator. Control for the actuator is provided by an electronic controller that is a part of the actuator.

The engine ECM communicates a desired throttle position to the fuel control valve controller in the form of a PWM signal. The PWM signal is generated by a signal driver at the ECM and the signal is sent to the controller for the fuel control valve.

Note: The desired throttle position is also communicated via the CAN data link as a throttle backup control.

The PWM signal that is used for the desired throttle position has a constant frequency of 500 Hz. At low engine idle, the signal will have a duty cycle of approximately 10 percent. At high engine idle with no load on the engine, the signal will have a duty cycle of approximately 20 to 25 percent. At high engine idle with a full load on the engine, the signal will have a duty cycle of approximately 50 to 60 percent.

The desired throttle position can be viewed on Caterpillar Electronic Technician (ET). View the status of the "Fuel Actuator Position Command" parameter in order to determine the desired throttle position of the engine. At low engine idle, the "Fuel Actuator Position Command" will be approximately 10 to 15 percent. At high engine idle with no load on the engine, the "Fuel Actuator Position Command" will be approximately 20 to 25 percent. At high engine idle with a full load on the engine, the "Fuel Actuator Position Command" will be approximately 40 to 50 percent.

Illustration 1	g03205016
Schematic of the PWM signal for the high-pressure fuel pump

Note: For a schematic and troubleshooting information that is related to the throttle backup control and the CAN data link, refer to Troubleshooting, "Data Link - Test".

Illustration 2	g03377752
Location of the connectors at the control box that are for the fuel control. (Control box may not be located on engine.) (1) Right rail connector (2) J1/P1 ECM connector (3) J2/P2 ECM connector

Illustration 3	g03332851
Location of the connectors at the high-pressure fuel pump (4) Connector for the fuel control valve electronic controller

Illustration 4	g01318105
Terminal locations for the high-pressure fuel pump at the P1 ECM connectors (P1-38) Throttle control (PWM signal) (P1-70) Keyswitch

Illustration 5	g02453085
Terminal locations for the high-pressure fuel pump at the P2 ECM connectors (P2-6) Filtered +Battery

Illustration 6	g01477832
Terminal locations for the high-pressure fuel pump at the right rail connectors (Terminal 16) Filtered +Battery from the ECM (Terminal 17) Return circuit from −Battery (Terminal 48) PWM signal (Terminal 70) Keyswitch

Illustration 7	g01478322
Terminal locations at the harness connector for the fuel system components (Terminal 2) Filtered +Battery from the ECM (Terminal 3) Return circuit from −Battery (Terminal 8) Keyswitch (Terminal 9) PWM signal

Table 2

Troubleshooting Test Steps	Values	Results
1. Check for an Active Diagnostic Code A. Connect Cat ET to the service tool connector. B. Restore the electrical power to the ECM. C. Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes Note: Wait at least 30 seconds in order for the diagnostic codes to become active. D. Determine if a diagnostic code has occurred several times. Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal. E. Look for one or more of the following diagnostic codes that are active or logged: - 18-7 - 18-8 - 18-9 - 18-11 - 18-12 - 91-8 - 1028-6 F. Remove the electrical power from the ECM.	Active Code	Results: No diagnostic codes are active. Repair: There may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct procedures for inspecting electrical connectors. Results: The 18-7 diagnostic code is active. Repair: The actual position and the desired position of the fuel actuator is not within specifications. Replace the fuel control valve. Results: The 18-8 diagnostic code is active. Repair: The fuel control valve controller detects a problem in the circuit for the PWM signal from the ECM. Proceed to Test Step 6. Results: The 18-9 diagnostic code is active. Repair: The ECM detects a problem with data link communications for the fuel control valve controller. Proceed to Test Step 2. Results: The 18-11 diagnostic code or the 18-12 diagnostic code is active. Repair: During a self test, the controller for the fuel control valve has detected an internal fault. Replace the fuel control valve.
2. Check the Supply Voltage at the Fuel Control Valve Controller A. Disconnect the connector at the fuel control valve controller. B. Restore the electrical power to the ECM. Ensure that the keyswitch is in the ON position. C. Use a multimeter to measure the supply voltage between terminal 1 (supply) and terminal 5 (return) on the harness side of the connector. D. Remove the electrical power from the ECM.	14.0 ± 1.5 VDC	Results: The supply voltage is 14.0 ± 1.5 VDC. The supply voltage is reaching the fuel control valve controller. Proceed to Test Step 3. Results: The supply voltage is not 14.0 ± 1.5 VDC. The supply voltage is not reaching the fuel control valve controller. Proceed to Test Step 4.

Table 3

Troubleshooting Test Steps	Values	Results
3. Check for Keyswitch Power at the Fuel Control Valve Controller A. Ensure that the connector for the fuel control valve controller has been disconnected. B. Restore the electrical power to the ECM. Ensure that the disconnect switch is in the ON position C. Use a multimeter to measure the keyswitch power between terminal 8 (keyswitch) on the harness side of the connector for the controller and the chassis ground. D. Remove the electrical power from the ECM. Restore the wiring to the original configuration.	24.0 ± 1.5 VDC	Results: The voltage at the keyswitch input is 24.0 ± 1.5 VDC. Repair: The voltage for the keyswitch and the supply are reaching the fuel control valve controller. The controller is being powered, but the controller is not communicating with the ECM. There may be a problem with the wiring for the CAN data link. Repair the CAN data link. Refer to Troubleshooting, "Data Link - Test" for information that is related to troubleshooting the circuit. Results: The voltage at the keyswitch input is not 24.0 ± 1.5 VDC. Repair: The keyswitch power is not reaching the fuel control valve controller. There is a problem in the keyswitch circuit. Repair the circuit. Refer to Troubleshooting, "Electrical Power Supply - Test" for information that is related to troubleshooting the keyswitch circuit.

Illustration 8	g01318220
Terminal locations at the connector for the fuel control valve controller (Terminal 1) Supply (Terminal 5) Return (Terminal 8) Keyswitch (Terminal 11) Throttle control (PWM signal)

Table 4

Troubleshooting Test Steps	Values	Results
4. Check the Integrity of the PWM Signal at the Controller for the Fuel Control Valve A. Remove the electrical power from the ECM. B. Disconnect the harness connector at the controller for the fuel control valve. C. Connect the leads of a multimeter between terminal 11 (throttle control (PWM signal)) and terminal 5 (return) at the connector for the controller D. Connect Cat ET to the service tool connector. E. Restore the electrical power to the ECM. Ensure that the keyswitch is in the ON position. F. Use the multimeter to measure the duty cycle and the frequency of the PWM signal. The correct value is approximately 10 percent duty cycle while the keyswitch is in the ON position and the engine is not running. The correct frequency of the signal is 500 Hz. G. Use Cat ET to override the "Fuel Actuator Position Command". Enter a value of 50 percent for the override parameter. Note: Wait at least 30 seconds in order for the override to become active. H. Use the multimeter to measure the duty cycle and the frequency of the PWM signal. The correct value is approximately 50 percent duty cycle with the "Fuel Actuator Position Command" set to a value of 50 percent. The correct frequency of the signal is 500 Hz I. Use Cat ET to override the "Fuel Actuator Position Command". Enter a value of 100 percent for the override parameter Note: Wait at least 30 seconds in order for the override to become active. J. Use the multimeter to measure the duty cycle and the frequency of the PWM signal. The correct value is approximately 90 percent duty cycle with the "Fuel Actuator Position Command" set to a value of 100 percent. The correct frequency of the signal is 500 Hz. K. Remove electrical power from the ECM. Restore all of the wiring to the original configuration.	Correct PWM Signal	Results: The duty cycle and frequency are correct for all measurements. Repair: OK - The ECM is generating the correct PWM signal and the wiring is OK. There is a problem with the fuel control valve controller. Replace the fuel control valve. Verify that the repair eliminates the original problem. Results: Not OK - The duty cycle is not consistent with the values that are given as the test results. There is a problem in the circuit for the PWM signal. There may be a problem with the ECM. Proceed to Test Step 5.

Table 5

Troubleshooting Test Steps	Values	Results
5. Check the Integrity of the PWM Signal at the ECM A. Disconnect the J1/P1 ECM connector. B. Use a wire removal tool to remove the wire from terminal location P1-38 (throttle control (PWM signal)). C. Fabricate a jumper wire that is long enough to create a test circuit at the ECM connector. Crimp a connector socket to the end of the jumper wire. Insert the jumper wire into the terminal location for the PWM signal. D. Connect the J1/P1 ECM connector. E. Carefully insert a black multimeter probe into terminal P1-18 (digital return) at the ECM connector. F. Connect Cat ET to the service tool connector. G. Restore the electrical power to the ECM. Ensure that the keyswitch is in the ON position. H. Use the multimeter to measure the duty cycle and the frequency of the PWM signal between the jumper wire and the multimeter probe. The correct value is approximately 10 percent duty cycle while the keyswitch is in the ON position and the engine is not running. The correct frequency of the signal is 500 Hz.	Correct PWM Signal	Results: The duty cycle and frequency are correct for all measurements. Repair: The ECM is generating the correct PWM signal. There is a problem in the harness wiring or in a connector between the ECM and the controller. Repair the harness or replace the harness. Verify that the repair eliminates the original problem. Results: The duty cycle is not consistent with the values that are given as the test results. Repair: The ECM is not generating the correct PWM signal for the controller. The ECM does not appear to be operating properly. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.

Table 6

I. Use Cat ET to override the "Fuel Actuator Position Command". Enter a value of 50 percent for the override parameter. Note: Wait at least 30 seconds in order for the override to become active. J. Use the multimeter to measure the duty cycle and the frequency of the PWM signal between the jumper wire and the multimeter probe. The correct value is approximately 50 percent duty cycle with the "Fuel Actuator Position Command" set to a value of 50 percent. The correct frequency of the signal is 500 Hz. K. Use Cat ET to override the "Fuel Actuator Position Command". Enter a value of 100 percent for the override parameter Note: Wait at least 30 seconds in order for the override to become active. L. Use the multimeter to measure the duty cycle and the frequency of the PWM signal between the jumper wire and the multimeter probe. The correct value is approximately 90 percent duty cycle with the "Fuel Actuator Position Command" set to a value of 100 percent. The correct frequency of the signal is 500 Hz. M. Remove electrical power from the ECM. Restore the wiring to the original configuration.

Correct PWM Signal

Results: The duty cycle and frequency are correct for all measurements. Repair: The ECM is generating the correct PWM signal. There is a problem in the harness wiring or in a connector between the ECM and the controller. Repair the harness or replace the harness. Verify that the repair eliminates the original problem. Results: The duty cycle is not consistent with the values that are given as the test results. Repair: The ECM is not generating the correct PWM signal for the controller. The ECM does not appear to be operating properly. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.