G3520B Engines Caterpillar

The master Electronic Control Module (ECM) contains the logic and the outputs for control of starting and shutdown of the engine. The logic for starting and stopping is customer programmable. The logic responds to inputs from the following components: engine control switch, emergency stop switch, remote start switch, data link and other inputs.

The fuel control relay is energize-to-run. To enable fuel flow to the engine, the relay for the Gas Shutoff Valve (GSOV) must be energized. The master ECM provides +battery voltage to the relay for the GSOV when the logic determines that fuel is required for engine operation. For engine shutdown, the master ECM removes the voltage from the fuel control relay. This stops the fuel flow.

The output circuit for the relay for the GSOV includes the emergency stop switch. The emergency stop switch has three sets of contacts. One set of contacts is for the GSOV. The contacts are normally closed. Pressing the emergency stop switch opens all of the sets of contacts. This removes the voltage from the fuel control relay. This stops the fuel flow.

The output circuit for the relay for the GSOV also includes the J19 connector. A 168-2028 Wiring Harness or a 237-5110 Wiring Harness must be connected to the J19 connector in order for the engine to start. The wiring harness must remain connected in order for the engine to run.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.

The most likely causes of a diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the GSOV. The least likely cause is a problem with the master ECM.

The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

17-12 Diagnostic Code

Under normal conditions, the master ECM shuts down the engine by removing electrical power from the GSOV. The master ECM continues the ignition until the engine reaches zero rpm. If the GSOV is working properly, the engine should reach zero rpm soon after the electrical power is removed from the GSOV.

If the engine continues to operate because of a faulty GSOV, the master ECM will disable the ignition. The master ECM will also activate a 17-12 diagnostic code.

Illustration 1	g00997783
Schematic of the output circuit for the fuel control relay

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 2	g00987150
Terminal box for the master ECM (1) J2/P2 connectors for the master ECM (2) J13/P13 connectors for the fuel control relay (3) Emergency stop switch (4) Wiring harness (5) 16 amp circuit breaker (6) Wiring harness for the customer

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

2. Thoroughly inspect the following connectors and the wiring harnesses for the connectors:
   • Master ECM J2/P2 connectors

   • J13/P13 connectors on the terminal box for the master ECM

   • Connectors for the fuel control relay

   1. Check the torque of the Allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).
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   Illustration 3	g00987167
   Harness side of the master ECM P2 connector (P2-11) Circuit driver for the fuel control relay (P2-21) Return

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   Illustration 4	g00920212
   Terminal box for the master ECM (7) Connector P13 for the fuel control relay (P13-A) Circuit driver for the fuel control relay (P13-B) Return

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the fuel control relay.
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   Illustration 5	g00869737
   Typical fuel control relay

   3. Check the harness and wiring for abrasion and pinch points from the fuel control relay to the master ECM.

Expected Result:

All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs, when possible. Replace parts, if necessary.

  STOP

Test Step 2. Check for Diagnostic Codes

1. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

2. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

3. Wait for 30 seconds and use Cat ET to check for an active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

   If there is an active "17-05 Fuel Shutoff Valve open circuit" diagnostic code, proceed to the "Results" for this Test Step. Otherwise, continue this procedure.

Note: The "17-05 Fuel Shutoff Valve open circuit" diagnostic code cannot be detected when the output for the fuel control relay is ON. The output is ON when the engine control is in the START mode and the engine speed is not zero.

4. Use Cat ET to check the logged diagnostic codes. If there is a "17-06 Fuel Shutoff Valve short to ground" or a "17-12 Fuel Shutoff Valve malfunction" diagnostic code, clear the code.

   Note: This diagnostic condition cannot be detected by the master ECM when the output for the fuel control relay is OFF. The output is OFF when the engine control is in the STOP mode.

5. To prevent the engine from starting, shut the gas supply OFF.

Note: To provide the output for the fuel control relay, the sequence for engine start-up must be initiated. Otherwise, a "17-06 Fuel Shutoff Valve short to ground" or a "17-12 Fuel Shutoff Valve malfunction" diagnostic code cannot be generated.

6. Set the engine control to the START mode for at least six seconds. Then set the engine control to the STOP mode.

7. Use Cat ET to look for a logged "17-06 Fuel Shutoff Valve short to ground" or a "17-12 Fuel Shutoff Valve malfunction" diagnostic code again.

Expected Result:

When the engine control was in the STOP mode, there was no active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

After the engine was cranked, there was no logged "17-06 Fuel Shutoff Valve short to ground" or "17-12 Fuel Shutoff Valve malfunction" diagnostic code.

Results:

• OK - No diagnostic codes were generated. The output for the fuel control relay seems to be OK at this time. The initial diagnostic code was probably caused by a poor electrical connection.

  Repair: If there is an intermittent problem that is causing the codes to be logged, refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK ("17-05 Fuel Shutoff Valve open circuit" diagnostic code) - A "17-05 Fuel Shutoff Valve open circuit" diagnostic code was activated. This can be caused by an actual open circuit or by a short circuit to the +battery side. Proceed to Test Step 3.

• Not OK ("17-06 Fuel Shutoff Valve short to ground" diagnostic code) - After the engine was cranked, a "17-06 Fuel Shutoff Valve short to ground" diagnostic code was generated. Proceed to Test Step 8.

• Not OK ("17-12 Fuel Shutoff Valve malfunction" diagnostic code) - After the engine was cranked, a "17-12 Fuel Shutoff Valve malfunction" diagnostic code was generated. The master ECM disabled the ignition.

  Repair: Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.Replace the fuel control relay.

  STOP

Test Step 3. Check for a Short Circuit to the +Battery Side

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Gaseous fuel is present. Personal Injury or Death can result from an open flame or spark igniting the gaseous fuel causing an explosion and/or fire. Always use a gas detector to determine the presence of gaseous fuel when maintaining and servicing. Contact you local gas provider immediately for assistance in the event of a leak.

Note: Open sparks can be generated during this test.

1. Make sure that no combustible gas is present in the surrounding atmosphere.

2. Ensure that the engine control is in the STOP mode.

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Illustration 6	g00891892
Fuel control relay (1) Connector for the fuel control relay (2) Relay

3. Disconnect connector (1) from relay (2). Then reconnect the connector. Listen for an audible click from the relay.

   If the ambient noise is too loud, touch the relay when the relay is reconnected in order to feel the vibration. The relay will vibrate when the relay is de-energized and energized.

Expected Result:

There is no audible click and/or vibration when the relay is disconnected and reconnected. The relay is not energized when the engine control is in the STOP mode.

Results:

• OK - There is no audible click and/or vibration when the relay is disconnected and connected. There is no short circuit to the +battery side. There is an open circuit. Proceed to Test Step 5.

• Not OK - There is an audible click and/or vibration when the relay is disconnected and connected. The relay is receiving power when the engine control is in the STOP mode. There is probably a short circuit to the +battery side in a connector or a wiring harness. Proceed to Test Step 4.

Test Step 4. Determine the Cause of the Energized Relay

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Gaseous fuel is present. Personal Injury or Death can result from an open flame or spark igniting the gaseous fuel causing an explosion and/or fire. Always use a gas detector to determine the presence of gaseous fuel when maintaining and servicing. Contact you local gas provider immediately for assistance in the event of a leak.

Note: Open sparks can be generated during this test.

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

2. Disconnect connector P13 from the terminal box.

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

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Illustration 7	g00891901
Typical fuel control relay (2) Connector for the fuel control relay (3) Relay

4. Disconnect connector (2) from relay (3). Then reconnect the connector. Listen for an audible click from the relay.

   If the ambient noise is too loud, touch the relay when the relay is reconnected in order to feel the vibration. The relay will vibrate when the relay is de-energized and energized.

Expected Result:

There is no audible click and/or vibration when the relay is disconnected and reconnected.

Results:

• OK - There is no audible click and/or vibration when the relay is disconnected and reconnected. The relay is not energized when the P13 connector is disconnected.

  Repair: Use the following procedure to determine whether the circuit driver for the relay is faulty:

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  Gaseous fuel is present. Personal Injury or Death can result from an open flame or spark igniting the gaseous fuel causing an explosion and/or fire. Always use a gas detector to determine the presence of gaseous fuel when maintaining and servicing. Contact you local gas provider immediately for assistance in the event of a leak.

  Note: Open sparks can be generated during this test.

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Reconnect the P13 connector to the terminal box.
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  Illustration 8	g00902478
  Harness side of the master ECM P2 connector (P2-11) Circuit driver for the fuel control relay (P2-21) Return

  3. Use a 151-6320 Wire Removal Tool to remove terminals P2-11 and P2-21.

  4. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.
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  Illustration 9	g00891901
  Typical fuel control relay (2) Connector for the fuel control relay (3) Relay

  5. Disconnect connector (2) from relay (3). Then reconnect the connector. Listen for an audible click from the relay.

     If the ambient noise is too loud, touch the relay when the relay is reconnected in order to feel the vibration. The relay will vibrate when the relay is de-energized and energized.

     If the relay is energized, there is a problem with a connector and/or wiring in the terminal box. Repair the wiring and/or the connector, when possible. Replace parts, if necessary.

     If the relay is not energized, there may be a problem with the master ECM. Continue with this procedure.

  6. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  7. Reinstall terminals P2-11 and P2-21. Pull on the wires in order to verify proper installation of the terminals.

  8. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

  9. Disconnect the connector from the fuel control relay. Then reconnect the connector. Listen for an audible click from the relay.

     If the ambient noise is too loud, touch the relay when the relay is reconnected in order to feel the vibration. The relay will vibrate when the relay is de-energized and energized.

     If the relay is not energized, there is an intermittent problem with a connector and/or the wiring. Refer to Troubleshooting, "Inspecting Electrical Connectors".

     If the relay is energized, there may be a problem with the master ECM.

     It is unlikely that the master ECM has failed. Exit this procedure and perform this procedure again. If the problem is not resolved, perform the following steps:

     Temporarily install a new master ECM. Refer to Troubleshooting, "Replacing the ECM".

     If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP

• Not OK - There is an audible click and/or vibration when the relay is disconnected and reconnected. The relay is energized when the P13 connector is disconnected. There is a short circuit to the +battery side in the engine harness.

  Repair: Repair the connector and/or wiring in the engine harness, when possible. Replace the engine harness, if necessary.

  STOP

Test Step 5. Create a Short Circuit in order to Check for an Open Circuit

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

2. Disconnect the fuel control relay's connector.

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Illustration 10	g00891959
Typical fuel control relay (1) Connector for the fuel control relay (2) Jumper wire

3. Install a jumper wire (2) into the two terminals of the relay's connector (1) on the engine harness.

4. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Note: The "17-05 Fuel Shutoff Valve open circuit" diagnostic code can only be detected when the output for the fuel control relay is OFF. The output is OFF when the engine control is in the STOP mode and the engine is not running.

5. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for a "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

Expected Result:

A "17-05 Fuel Shutoff Valve open circuit" diagnostic code was not generated when the jumper wire was installed.

Results:

• OK - A "17-05 Fuel Shutoff Valve open circuit" diagnostic code was not generated when the jumper wire was installed. The harness and the ECM are OK. There is a problem with the relay.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Remove the jumper wire from the relay's connector on the engine harness.

  3. Inspect the relay's connectors for damage, for moisture, and for corrosion.

  4. Make repairs, as needed.
  If the problem is not resolved, replace the fuel control relay.

  STOP

• Not OK - A "17-05 Fuel Shutoff Valve open circuit" diagnostic code was generated when the jumper wire was installed. There may be an open circuit in the engine harness. Proceed to Test Step 6.

Test Step 6. Check the Engine Harness

1. Ensure that the engine control is in the OFF/RESET mode and that the 16 amp circuit breaker is OFF.

2. Disconnect the P13 connector from the terminal box. Inspect the P13 and J13 connectors for damage, moisture, and corrosion. Make repairs, if necessary.

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Illustration 11	g00891989
Terminal box for the master ECM (1) J13 connector for the fuel control relay (2) Jumper wire

3. Install a jumper wire (2) into the two terminals of the J13 connector (1) .

4. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Note: The "17-05 Fuel Shutoff Valve open circuit" diagnostic code can only be detected when the output for the fuel control relay is OFF. The output is OFF when the engine control is in the STOP mode and the engine is not running.

5. Wait for 30 seconds and use Cat ET to check for an active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

Expected Result:

There is no active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

Results:

• OK - When the jumper wire was installed, there was no active "17-05 Fuel Shutoff Valve open circuit" diagnostic code. There is a problem in the engine harness.

  Repair: Repair the engine harness, when possible. Replace the engine harness, if necessary.

  STOP

• Not OK - When the jumper wire was installed, a "17-05 Fuel Shutoff Valve open circuit" diagnostic code was activated. The master ECM did not detect the jumper wire in the J13 connector. There is a problem in the terminal box. Proceed to test Step 7.

Test Step 7. Check the Master ECM

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

2. Remove the jumper wire from the J13 connector.

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Illustration 12	g00902478
Harness side of the master ECM P2 connector (P2-11) Circuit driver for the fuel control relay (P2-21) Return

3. Use the 151-6320 Wire Removal Tool to remove terminals P2-11 and P2-21.

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Illustration 13	g00902503
Harness side of the master ECM P2 connector (1) Jumper wire (P2-11) Circuit driver for the fuel control relay (P2-21) Return

4. Install a jumper wire (1) into terminals P2-11 and P2-21. Pull on the jumper wire in order to verify proper installation.

5. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

Note: The "17-05 Fuel Shutoff Valve open circuit" diagnostic code can only be detected when the output for the fuel control relay is OFF. The output is OFF when the engine control is in the STOP mode and the engine is not running.

6. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for an active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

Expected Result:

There is no active "17-05 Fuel Shutoff Valve open circuit" diagnostic code.

Results:

• OK - When the jumper wire was installed, there was no active "17-05 Fuel Shutoff Valve open circuit" diagnostic code. The master ECM detects the jumper wire at the P2 connector. However, the master ECM did not detect the jumper wire at the J13 connector. There is a problem between the P2 connector and the J13 connector.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P2 connector.

  3. Reinstall the terminals into P2-11 and P2-21. Pull on the wires in order to verify proper installation of the terminals.

  4. Disconnect the J2/P2 connectors. Inspect the connectors for damage, for moisture, and for corrosion.

  5. Thoroughly inspect the J13 connector for the engine harness.

  6. Use an ohmmeter to measure the resistance between terminals P2-11 and J13-A. Also, measure the resistance between terminals P2-21 and J13-B.

     If the resistance measurements are less than 5 ohms, the circuit has good continuity. Otherwise, there is an open circuit.

     Make repairs, if necessary.

  STOP

• No - When the jumper wire was installed, a "17-05 Fuel Shutoff Valve open circuit" diagnostic code was activated. The master ECM did not detect the jumper wire. There is a problem with the master ECM.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Use a 151-6320 Wire Removal Tool to remove the jumper wire from the P2 connector.

  3. Reinstall the terminals into P2-11 and P2-21. Pull on the wires in order to verify proper installation of the terminals.

  4. Replace the master ECM according to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP

Test Step 8. Create an Open Circuit in order to Check for a Short Circuit to Ground

1. Set the engine control to the OFF/RESET mode.

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Illustration 14	g00891892
Typical fuel control relay (1) Connector for the fuel control relay (2) Relay

2. Disconnect connector (1) from relay (2) .

3. Set the engine control to the STOP mode.

4. Use Cat ET to clear the logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code.

5. To prevent the engine from starting, shut OFF the main gas supply.

Note: To provide the output for the fuel control relay, the sequence for engine start-up must be initiated. Otherwise, a "17-06 Fuel Shutoff Valve short to ground" diagnostic code cannot be generated.

6. Set the engine control to START for at least six seconds. Then set the engine control to the STOP mode.

7. Use Cat ET to look for a logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code again.

Expected Result:

A "17-06 Fuel Shutoff Valve short to ground" was not generated.

Results:

• OK - When the relay was connected, a "short to ground" diagnostic code was generated. When the relay was disconnected, no "short to ground" diagnostic code was generated. There is a problem with the relay.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Inspect the relay's connectors for damage and/or for corrosion.

  3. Make repairs, as needed.
  If the problem is not resolved, replace the relay.

  STOP

• Not OK - A "short to ground" diagnostic code was generated when the relay was disconnected. Proceed to Test Step 9.

Test Step 9. Create an Open Circuit at the Terminal Box for the Master ECM

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

2. Disconnect connector P13 from the terminal box.

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

4. Use Cat ET to clear the logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code.

5. To prevent the engine from starting, shut OFF the main gas supply.

Note: To provide the output for the fuel control relay, the sequence for engine start-up must be initiated. Otherwise, a "17-06 Fuel Shutoff Valve short to ground" diagnostic code cannot be generated.

6. Set the engine control to the START mode for at least six seconds. Then set the engine control to the STOP mode.

7. Use Cat ET to look for a logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code again.

Expected Result:

A "17-06 Fuel Shutoff Valve short to ground" was not generated.

Results:

• OK - A "17-06 Fuel Shutoff Valve short to ground" diagnostic code was not generated when the P13 connector was disconnected. There is a problem in the engine harness.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Reconnect the P13 connector.

  3. Repair the engine harness, when possible. Replace the harness, if necessary.

  STOP

• Not OK - A "17-06 Fuel Shutoff Valve short to ground" diagnostic code was generated when the P13 connector was disconnected. There is probably a short circuit to ground in the terminal box.

  Repair: Reconnect the P13 connector.

  Proceed to Test Step 10.

Test Step 10. Check the Master ECM

1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

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Illustration 15	g00902504
Harness side of the master ECM P2 connector (P2-11) Circuit driver for the fuel control relay

2. Use the 151-6320 Wire Removal Tool to remove terminal (P2-11) .

3. Switch the 16 amp circuit breaker ON. Set the engine control to the STOP mode.

4. Use Cat ET to clear the logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code.

5. To prevent the engine from starting, shut OFF the main gas supply.

Note: To provide the output for the fuel control relay, the sequence for engine start-up must be initiated. Otherwise, a "17-06 Fuel Shutoff Valve short to ground" diagnostic code cannot be generated.

6. Set the engine control to the START mode for at least six seconds. Then set the engine control to the STOP mode.

7. Use Cat ET to look for a logged "17-06 Fuel Shutoff Valve short to ground" diagnostic code again.

Expected Result:

The "17-06 Fuel Shutoff Valve short to ground" diagnostic code was not generated.

Results:

• OK - When the output to the relay was disconnected from the P2 connector, the "17-06 Fuel Shutoff Valve short to ground" diagnostic code was not generated. However, a "short to ground" diagnostic code was generated when the P13 connector was disconnected from the terminal box. There is a problem in the terminal box between the P2 connector and the P13 connector.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Reinstall the terminal that was removed from P2-11. Pull on the wire in order to verify proper installation of the terminal.

  3. Repair the terminal box's harness, when possible. Replace the harness, if necessary.

  STOP

• Not OK - A "17-06 Fuel Shutoff Valve short to ground" diagnostic code was generated when the output to the relay was disconnected from the P2 connector. There seems to be a problem with the master ECM.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

  2. Reinstall the terminal that was removed from P2-11. Pull on the wire in order to verify proper installation of the terminal.

  3. Replace the master ECM according to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP