G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot 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 the engine is customer programmable. The logic responds to inputs from the following components:

• ECM

• Emergency stop switch

• Remote start switch

• Data link

• Other inputs

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. Continue troubleshooting 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 1	g01393576
Schematic for the air starting motor system

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Set the engine control to the OFF/RESET position.
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   Illustration 2	g01392084
   Location of the ECM connectors for the starting motor relay (typical left front side engine view) (1) J2/P2 ECM connectors

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   Illustration 3	g01393572
   Location of the connectors for the starting motor relay (2) Starting motor relay (3) Connector for the starting motor relay

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

2. Thoroughly inspect ECM connectors (1). Also, thoroughly inspect connectors (3) that are for starting motor relay (2).

   1. Check the allen head screw for each of the ECM connectors for the proper torque.
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      Illustration 4	g01393581
      Terminal locations at the P2 ECM connector for the starting motor circuit (P2-10) Starting motor (P2-20) Return

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

   3. Check the harness and wiring for abrasion and for pinch points from the starting system 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. Establish communication between the Caterpillar Electronic Technician (ET) and the ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.

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

2. Wait for 30 seconds and 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.

3. Check the logged codes. If there is a logged 444-6 diagnostic code, clear the code.

4. To prevent the engine from starting, shut off the 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 "COOLDOWN/STOP" position to the "START" position. The output remains on until the crank terminate relay is energized.

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

6. Check for a logged 444-6 diagnostic code.

Expected Result:

When the engine control was in the COOLDOWN/STOP position, 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.

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

  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. Proceed to Test Step 3.

• Not OK (444-6 diagnostic code) - After the engine was cranked, a 444-6 diagnostic code was activated. Proceed to Test Step 7.

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 your 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. Verify that the engine control is in the COOLDOWN/STOP position.

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 position.

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 position. Proceed to Test Step 6.

Test Step 4. Create a Short Circuit at the Starting Motor Relay

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

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

3. Install a jumper wire between the two terminals of the harness connector at the air start relay.

4. Set the engine control to the COOLDOWN/STOP position.

5. Wait for 30 seconds. Check 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 position.

  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. Make repairs, as needed.
  If the problem is not resolved, 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. Verify that the engine control is in the OFF/RESET position.

2. Remove the wires from terminal locations P2-10 and P2-20 at the ECM connector.

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

4. Set the engine control to the COOLDOWN/STOP position.

5. Wait for 30 seconds. Check 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 ECM connector. However, the ECM did not detect the jumper wire at the relay's connector. There is a problem with the wiring between the P2 ECM connector and the connector for the air start relay.

  Repair: Perform the following procedure:

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

  2. Remove the jumper wire from the P2 ECM connector.

  3. Restore the wiring at the P2 ECM connector. Pull on the wires in order to verify proper installation of the terminals.

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

  STOP

• Not OK - 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 position.

  2. Remove the jumper wire from the P2 connector.

  3. Restore the wiring at the P2 ECM connector. Pull on the wires in order to verify proper installation of the terminals.
  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 at the ECM Connector

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

2. Remove the wires from terminal locations P2-10 and P2-20 at the ECM connector.

3. Set the engine control to the COOLDOWN/STOP position.

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

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

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 position.

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 position.

  2. Restore the wiring at the P2 ECM connector. Pull on the wires in order to verify proper installation of the terminals.
  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.

  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 position.

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

3. Set the engine control to the COOLDOWN/STOP position.

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 COOLDOWN/STOP position to the START position. The output remains ON until the crank terminate relay is energized.

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

6. Check for a logged 444-6 diagnostic code.

Expected Result:

A 444-6 diagnostic code 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 position.

  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. Perform the necessary repairs.
  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 for Proper Operation of the ECM

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

2. Remove the wires from terminal locations P2-10 and P2-20 at the ECM connector.

3. Set the engine control to the COOLDOWN/STOP position.

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 COOLDOWN/STOP position to the START position. The output remains ON until the crank terminate relay is energized.

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

6. Check for a logged 444-6 diagnostic code.

Expected Result:

A 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.

  Repair: Perform the following procedure:

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

  2. Restore the wiring at the P2 ECM connector. Pull on the wires in order to verify proper installation of the terminals.

  3. Repair the harness, when possible. Replace parts, 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 position.

  2. Restore the wiring at the P2 ECM connector. Pull on the wires in order to verify proper installation of the terminals.
  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