G3520B Industrial Engine Caterpillar


ECM Output Circuit (Starting Motor)

Usage:

G3520B GET
System Operation Description:

The ECM contains the logic and the outputs for starting the engine. The logic for starting the engine is customer programmable. The logic responds to inputs from the following components: engine control, emergency stop switch, remote start switch, data link and other inputs.

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 the diagnostic code are a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with the fuel control 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.

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.

If the engine is equipped with a prelubrication system, an air start may not occur until the prelubrication is complete. If there is a problem with the prelubrication system, the air start may not occur. There are no diagnostics for the prelubrication system. Refer to Systems Operation, Testing and Adjusting, "Air Starting System (Starting with an Air Prelube Pump)".




Illustration 1g01091719

Schematic for the air starting system

Test Step 1. Inspect the Electrical Connectors and Wiring




    Illustration 2g01087625

    Terminal box

    (1) J2/P2 connectors for the master ECM

    (2) J8/P8 connectors for the harness from the starting system

  1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.



    Illustration 3g01087633

    Typical air start relay and connector

    (3) Air start relay

    (4) Connector for the air start relay

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

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

    • J2/P2 connectors

    • J8/P8 connectors on the terminal box

    • Connectors for the air start 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).



      Illustration 4g00993907

      Harness side of the P2 connector

      (P2-10) Start command

      (P2-20) Return for the start command




      Illustration 5g01087634

      Harness side of the P8 connector

      (P8-d) Start command

      (P8-n) Return for the start command

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

    1. Check the harness and wiring for abrasion and for pinch points from the starting system 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".

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

    Note: The "444-05 Start Relay open circuit" 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.

  1. Wait for 30 seconds and use Cat ET to check for an active "444-05 Start Relay open circuit" diagnostic code.

    If there is an active "444-05 Start Relay open circuit" diagnostic code, proceed to the "Results" for this Test Step. Otherwise, continue this procedure.

  1. Use Cat ET to check the logged diagnostic codes. If there is a "444-06 Start Relay short to ground" diagnostic code, clear the code.

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

    Note: The "444-06 Start Relay short to ground" 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.

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

  1. Use Cat ET to look for a logged "444-06 Start Relay short to ground" diagnostic code again.

Expected Result:

When the engine control was in the STOP mode, there was no active "444-05 Start Relay open circuit" diagnostic code.

After the engine was cranked, there was no logged "444-06 Start Relay short to ground" 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, "Inspecting Electrical Connectors".

    Stop.

  • Not OK ("444-05 Start Relay open circuit" diagnostic code) - A "444-05 Start Relay 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 ("444-06 Start Relay short to ground" diagnostic code) - After the engine was cranked, a "444-06 Start Relay short to ground" diagnostic code was activated. Proceed to Test Step 7.

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

    ------ WARNING! ------

    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.

  1. Verify that the engine control is in the STOP mode.

  1. 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. Remove the electrical power from the engine.

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

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

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

  1. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for a "444-05 Start Relay open circuit" diagnostic code.

Expected Result:

A "444-05 Start Relay open circuit" diagnostic code was not activated when the jumper wire was installed.

Results:

  • OK - A "444-05 Start Relay open circuit" 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. Remove the electrical power from the engine.

    1. Remove the jumper wire from the harness connector.

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

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

    Stop.

  • Not OK - A "444-05 Start Relay open circuit" 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. Verify that the engine control is in the OFF/RESET mode and that the electrical power is removed from the engine.

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

  1. Install a jumper wire into terminals P2-10 and P2-20. Pull on the jumper wire in order to verify proper installation.

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

  1. Wait for 30 seconds and use the "Active Diagnostic" screen of Cat ET to look for an active "444-05 Start Relay open circuit" diagnostic code.

Expected Result:

There is no active "444-05 Start Relay open circuit" diagnostic code.

Results:

  • OK - When the jumper wire was installed, there was no active "444-05 Start Relay open circuit" 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 problem could be between the P2 connector and the J8 connector. Alternatively, the problem could be in the P8 connector or the wiring that is connected to the P8 connector.

    Repair: Perform the following procedure:

    1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

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

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

    1. Repair the harness, when possible. Replace parts, if necessary.

    Stop.

  • Not OK - When the jumper wire was installed, a "444-05 Start Relay open circuit" 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. Remove the electrical power from the engine.

    1. Remove the jumper wire from the P2 connector.

    1. 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, "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.

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. Remove the electrical power from the engine.

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

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

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

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

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. Remove the electrical power from the engine.

    1. 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, "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 - 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 J8 connector. Alternatively, the problem could be in the P8 connector or the wiring that is connected to the P8 connector.

    Repair: Repair the harness, when possible. Replace parts, 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. Remove the electrical power from the engine.

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

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

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

    Note: The "444-06 Start Relay short to ground" 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.

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

  1. Use Cat ET to look for a logged "444-06 Start Relay short to ground" diagnostic code again.

Expected Result:

A "444-06 Start Relay short to ground" was not activated.

Results:

  • OK - A "444-06 Start Relay short to ground" 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. Remove the electrical power from the engine.

    1. Remove the jumper wire from the connector.

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

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

    Stop.

  • Not OK - A "444-06 Start Relay short to ground" 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. Remove the electrical power from the engine.

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

  1. Restore the electrical power to the engine. Set the engine control to the STOP mode.

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

    Note: The "444-06 Start Relay short to ground" 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.

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

  1. Use Cat ET to look for a logged "444-06 Start Relay short to ground" diagnostic code again.

Expected Result:

The "444-06 Start Relay short to ground" diagnostic code was not activated.

Results:

  • OK - When the wiring was disconnected from the ECM, a "444-06 Start Relay short to ground" diagnostic code was not activated. There is a problem with the wiring. The problem could be between the P2 connector and the J8 connector. Alternatively, the problem could be in the P8 connector or the wiring that is connected to the P8 connector.

    Repair: Perform the following procedure:

    1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

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

    1. Repair the harness, when possible. Replace parts, if necessary.

    Stop.

  • Not OK - When the wiring was disconnected from the ECM, a "444-06 Start Relay short to ground" 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. Remove the electrical power from the engine.

    1. 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, "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.

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