G3516C, G3516E, and G3512E Generator Set Engines Caterpillar

Use this procedure to troubleshoot suspect problems with the circuit for the starting system.

This procedure covers the following diagnostic codes:

• 444-5 Starter Motor Relay : Current Below Normal

• 444-6 Starter Motor Relay : Current Above Normal

The Electronic Control Module (ECM) contains the logic and the outputs for starting the engine. The logic for starting 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.

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

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

Electric Start

The ECM supplies +Battery voltage to two magnetic switches when the logic determines that it is necessary. Each magnetic switch provides +Battery voltage to a solenoid on an electric starting motor.

The ECM removes the voltage when the crank terminate relay is energized. The voltage is also removed if the customer programmable "Overcrank Time" has expired.

Air Start

The ECM supplies +Battery voltage to the air start relay when the logic determines that it is necessary. The ECM removes the voltage when the crank terminate relay is energized. The voltage is also removed if the customer programmable "Overcrank Time" has expired.

Illustration 1	g01534716
Schematic for the electric starting system

Illustration 2	g01325950
Schematic for the air start system

Test Step 1. Inspect the Electrical Connectors and Wiring

1. Remove the electrical power from the engine.

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

2. Thoroughly inspect the following connectors and the wiring harnesses for the connectors:

   • J2/P2 connectors

   • J7/P7 connectors

   1. Check the torque of the allen head screw for the ECM connectors.
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      Illustration 3	g01055043
      Harness side of the P2 connector (P2-10) Start command (P2-20) Return for the start command

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the starting motor relay.

   3. Check the harness and wiring for abrasion and for pinch points from the starter motor relay to the 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 35 amp circuit breaker ON. Set the engine control to the STOP mode.

   Note: The 444-5 diagnostic code can only be detected when the output for the start command is off. The output is normally off when the engine control is in the STOP mode or when the crank terminate relay is energized.

3. Wait for 30 seconds and use Cat ET to check for an active 444-5 diagnostic code.

   If there is an active 444-5 diagnostic code, proceed to the “Results” for this Test Step. Otherwise, continue this procedure.

4. Use Cat ET to check the logged diagnostic codes. If there is a logged 444-6 diagnostic code, clear the code.

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

   Note: The 444-6 diagnostic code can only be detected when the output for the start command is ON. The output is normally ON when the engine control is set from the STOP mode to the START mode. The output remains ON until the crank terminate relay is energized.

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 444-6 diagnostic code again.

Expected Result:

When the engine control was in the STOP mode, there was no active 444-5 diagnostic code.

After the engine was cranked, there was no logged 444-6 diagnostic code.

Results:

• OK - No diagnostic codes were activated. The output for the start command 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, "Electrical Connectors - Inspect".

  STOP

• Not OK (444-5 diagnostic code) - A 444-5 diagnostic code was activated. This can be caused by an actual open circuit or by a short circuit to the +Battery side. If the engine is equipped with an air start system, proceed to Test Step 3. If the engine is equipped with an electric starting system, proceed to Test Step 9.

• Not OK (444-6 diagnostic code) - After the engine was cranked, a 444-6 diagnostic code was activated. If the engine is equipped with an air start system, proceed to Test Step 7. If the engine is equipped with an electric starting system, proceed to Test Step 10.

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.

3. Disconnect the connector from the air start relay. Then reconnect the connector. Listen for an audible click from the relay.

   If the ambient noise is too loud, touch the air start 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 air start 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 air start relay is disconnected and connected. There is no short circuit to the +Battery side. There is an open circuit. Proceed to Test Step 4.

• Not OK - There is an audible click and/or vibration when the air start relay is disconnected and connected. The relay is receiving power when the engine control is in the STOP mode. Proceed to Test Step 6.

Test Step 4. Create a Short Circuit in order to Check for an Open Circuit

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Disconnect the harness connector from the air start relay.

3. Install a jumper wire into the two terminals of the harness connector for the air start relay.

4. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

5. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for a 444-5 diagnostic code.

Expected Result:

A 444-5 diagnostic code was not activated when the jumper wire was installed.

Results:

• OK - A 444-5 diagnostic code was not activated when the jumper wire was installed. The ECM detected the short circuit. The harness and the ECM are OK. There is a problem with the air start relay.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

  2. Remove the jumper wire from the harness connector.

  3. Inspect the relay's connector and the harness connector for the relay. Check for damage, for moisture, and for corrosion.

  4. If the connectors are OK, replace the air start relay.

  STOP

• Not OK - A 444-5 diagnostic code was activated when the jumper wire was installed. The ECM did not detect the short circuit. Proceed to Test Step 5.

Test Step 5. Check the ECM

1. Ensure that the engine control is in the OFF/RESET mode and that the 35 amp circuit breaker is OFF.

2. Use a 151-6320 Wire Removal Tool to remove terminals from P2-10 and fromP2-20.

3. Install a jumper wire between terminal P2-10 and terminal P2-20. Pull on the jumper wire in order to verify proper installation.

4. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

5. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for an active 444-5 diagnostic code.

Expected Result:

There is no active 444-5 diagnostic code.

Results:

• OK - When the jumper wire was installed, there was no active 444-5 diagnostic code. The ECM detects the jumper wire at the P2 connector. However, the ECM did not detect the jumper wire at the relay's connector. There is a problem with the wiring. The open could be between the P2 connector and the J7 connector. Alternatively, the open could be in the P7 connector or the wiring that is connected to the P7 connector.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

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

  3. Check continuity between the ECM and the air start relay for each of the wires in order to determine the open circuit condition.

  4. Repair the harness, when possible. Replace the harness, if necessary.

  STOP

• No - When the jumper wire was installed, a 444-5 diagnostic code was activated. The ECM did not detect the jumper wire. There is a problem with the ECM.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

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

  3. Reinstall terminals P2-10 and P2-20. Pull on the wires in order to verify proper installation of the terminals.
  It is unlikely that the 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 ECM. Refer to Troubleshooting, "ECM - Replace".

  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, "ECM - Replace".

  STOP

Test Step 6. Create an Open Circuit in order to Check for a Short Circuit

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Use a 151-6320 Wire Removal Tool to remove terminals P2-10 and P2-20.

3. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

4. To prevent the engine from starting, shut off the main gas supply.

5. Set the engine control to the START mode for at least six seconds. Then set the engine control to the STOP mode. Listen for an audible click from the relay.

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 - When the ECM was connected, the relay was receiving power. When the ECM was not connected, the relay was not receiving power. There may be a problem with the ECM.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

  2. Reinstall terminals P2-10 and P2-20. Pull on the wires in order to verify proper installation of the terminals.
  It is unlikely that the 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 ECM. Refer to Troubleshooting, "ECM - Replace".

  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, "ECM - Replace".

  STOP

• Not OK - When the ECM was connected, the relay was receiving power. When the ECM was not connected, the relay was still receiving power. There is a problem with the wiring. The problem could be between the P2 connector and the J7 connector. Alternatively, the problem could be in the P7 connector or the wiring that is connected to the P7 connector.

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

  STOP

Test Step 7. Create an Open Circuit at the Air Start Relay

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Disconnect the harness connector from the air start relay.

3. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

4. To prevent the engine from starting, shut off the main gas supply.

   Note: The 444-6 diagnostic code can only be detected when the output for the start command is on. The output is normally on when the engine control is set from the STOP mode to the START mode. The output remains on until the crank terminate relay is energized.

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

6. Use Cat ET to look for a logged 444-6 diagnostic code again.

Expected Result:

A 444-6 diagnostic was not activated.

Results:

• OK - A 444-6 diagnostic code was not activated when the air start relay was disconnected. There is a problem with the air start relay.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

  2. Remove the jumper wire from the connector.

  3. Inspect the connectors for the air start relay. Check for damage, for moisture, and for corrosion.

  4. Make repairs, as needed.
  If the problem is not resolved, replace the air start relay.

  STOP

• Not OK - A 444-6 diagnostic code was activated when the air start relay was disconnected. The air start relay is OK. Proceed to Test Step 8.

Test Step 8. Check the ECM

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

2. Use the 151-6320 Wire Removal Tool to remove terminals P2-10 and P2-20.

3. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

4. To prevent the engine from starting, shut off the main gas supply.

   Note: The 444-6 diagnostic code can only be detected when the output for the start command is on. The output is normally on when the engine control is set from the STOP mode to the START mode. The output remains on until the crank terminate relay is energized.

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

6. Use Cat ET to look for a logged 444-6 diagnostic code.

Expected Result:

The 444-6 diagnostic code was not activated.

Results:

• OK - When the wiring was disconnected from the ECM, a 444-6 diagnostic code was not activated. There is a problem with the wiring. The problem could be between the P2 connector and the J7 connector. Alternatively, the problem could be in the P7 connector or the wiring that is connected to the P7 connector.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

  2. Reinstall terminals P2-10 and P2-20. Pull on the wires in order to verify proper installation of the terminals.

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

  STOP

• Not OK - When the wiring was disconnected from the ECM, a 444-6 diagnostic code was activated. There seems to be a problem with the ECM.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

  2. Reinstall terminals P2-10 and P2-20. Pull on the wires in order to verify proper installation of the terminals.
  It is unlikely that the 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 ECM. Refer to Troubleshooting, "ECM - Replace".

  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, "ECM - Replace".

  STOP

Test Step 9. Check the "SM" Circuit Breaker

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Illustration 4	g01055051
"SM" circuit breaker (2.5 amp)

1. Verify that the "SM" circuit breaker is in the ON position.

Expected Result:

The "SM" circuit breaker is in the ON position.

Results:

• OK - The "SM" circuit breaker is in the ON position. Proceed to Test Step 10.

• Not OK - The "SM" circuit breaker is not in the ON position.

  Repair: Switch the "SM" circuit breaker to the ON position.

  If the circuit breaker remains in the ON position, the problem may be resolved. Perform the following procedure:

  1. Verify that the 35 amp circuit breaker is ON. Set the engine control to the STOP mode.

     Note: The 444-5 diagnostic code can only be detected when the output for the start command is off. The output is normally off when the engine control is in the STOP mode or when the crank terminate relay is energized.

  2. Wait for 30 seconds and use Cat ET to check for an active 444-5 diagnostic code.

  If there is no active 444-5 diagnostic code, the problem appears to be resolved. Resume normal operation. If there is an active 444-5 diagnostic code, proceed to Test Step 10.

Test Step 10. Inspect the Inside of the Power Distribution Box

1. Disconnect the +24 V power supply from the engine.
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   Illustration 5	g00931289
   Terminals on the power distribution box

2. Verify that the power is disconnected by checking for voltage at the "+" and "-" terminals on the power distribution box. The voltage on the terminals should be zero VDC.
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   Illustration 6	g00931303
   Fasteners for the power distribution box

3. Remove seven bolts and nuts. Open the power distribution box.

4. Inspect the inside of the power distribution box. Check for moisture and for corrosion. Verify that each electrical connection inside the power distribution box is securely connected.

Expected Result:

The inside of the power distribution box does not have moisture or corrosion. All of the electrical connections inside the power distribution box are securely connected.

Results:

• OK - The inside of the power distribution box does not have moisture or corrosion. All of the electrical connections inside the power distribution box are securely connected. Proceed to Test Step 11.

• Not OK - The inside of the power distribution box has moisture or corrosion and/or there is a loose electrical connection.

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

  STOP

Test Step 11. Check for an Open Circuit

1. Use a 151-6320 Wire Removal Tool to remove terminals P2-10 and P2-20.
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   Illustration 7	g01534813
   Section view of the power distribution box (1) Coil terminals on the magnetic switches (2) Terminals on the "SM" circuit breaker

2. Use a multimeter to check for an open circuit between the points that are listed in Table 1:
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   Table 1

   Points to Check for an Open Circuit
   Point	Point
   P2-20	"+" terminal on the power distribution box
   P2-10	"+" terminal on the power distribution box
   Each coil terminal (1) on each magnetic switch	"+" terminal on the power distribution box
   Each terminal (2) on the "SM" circuit breaker	"+" terminal on the power distribution box

Expected Result:

All of the measurements are an open circuit.

Results:

• OK - All of the measurements are an open circuit. There is not a short circuit to the +Battery. Proceed to Test Step 12.

• Not OK - At least one measurement is not an open circuit. There is a short circuit to the +Battery.

  Repair: Repair the wiring and/or the connection, when possible. Replace parts, if necessary.

  STOP

Test Step 12. Check for a Short Circuit

1. Verify that the "SM" circuit breaker is in the ON position.

2. Use a multimeter to check for a short circuit between the points that are listed in Table 2:

   Note: Refer to Illustration 1, if necessary.

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   Table 2

   Points to Check for a Short Circuit
   Point	Point
   P2-10	The connection for the "SM"circuit breaker that is connected to wire "P6B0A-RD"
   One of the connections for the "SM" circuit breaker	The other connection for the "SM" circuit breaker
   The connection for the "SM" circuit breaker that is connected to wire "P6B0B-RD"	The coil terminal of each magnetic switch that is connected to wire "C990-RD"
   The coil terminal of each magnetic switch that is connected to wire "C991-RD"	P2-20

Expected Result:

All of the measurements are less than two Ohms.

Results:

• OK - All of the measurements are less than two Ohms. There is not an open circuit. Proceed to Test Step 13.

• Not OK - At least one measurement is more than two Ohms. There is a problem with the wiring or with the "SM" circuit breaker.

  Repair: Repair the wiring and/or the connection, when possible. Replace parts, if necessary.

  STOP

Test Step 13. Check the Coils for the Magnetic Switches

1. Use a multimeter to measure the resistance of the coil for each magnetic switch.

Expected Result:

The resistance of each coil is between 16 and 20 Ohms.

Results:

• OK - The resistance of each coil is between 16 Ohms and 20 Ohms. The coil resistance for each magnetic switch is correct.

  Repair:

  1. Install the seven bolts and nuts for the power distribution box.

  2. Reconnect the +24 V power supply to the engine.

  Proceed to Test Step 14.

• Not OK - The resistance of a coil is not between 16 Ohms and 20 Ohms. The resistance of a coil for a magnetic switch is incorrect.

  Repair: Replace the magnetic switch. Verify that the original problem is resolved.

  STOP

Test Step 14. Check the Operation of the ECM

1. Use a 151-6320 Wire Removal Tool to remove terminals from P2-10 and fromP2-20.

2. Verify that the 35 amp circuit breaker is ON. Verify that the "SM" circuit breaker is ON.

   Note: The 444-5 diagnostic code can only be detected when the output for the start command is off. The output is normally off when the engine control is in the STOP mode or when the crank terminate relay is energized.

3. Set the engine control to the STOP mode.

   A 444-5 diagnostic code should be active.

4. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

5. Ensure that the engine control is in the OFF/RESET mode and that the 35 amp circuit breaker is OFF.

6. Install a jumper wire between terminal P2-10 and terminal P2-20. Pull on the jumper wire in order to verify proper installation.

7. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

   Note: The 444-6 diagnostic code can only be detected when the output for the start command is on. The output is normally on when the engine control is set from the STOP mode to the START mode. The output remains on until the crank terminate relay is energized.

8. Set the engine control to the START mode. Look for a 444-6 diagnostic code.

   A 444-6 diagnostic code should be active.

9. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.

Expected Result:

The diagnostic codes were activated.

Results:

• OK - The diagnostic codes were activated. The ECM is operating correctly.

  Repair: The problem is in the wiring between the ECM and the coils of the magnetic switches. Repair the wiring and/or the connectors.

  STOP

• Not OK - A diagnostic code was not activated. There may be a problem with the ECM.

  Repair: It is unlikely that the 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 ECM. Refer to Troubleshooting, "ECM - Replace".

  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, "ECM - Replace".

  STOP