3512C Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the air shutoff system or if any one of the diagnostic codes in Table 1 is active or easily repeated.

The ECM has the ability to stop the engine by shutting off the air supply in an emergency situation. The ECM activates the air shutoff solenoid which activates the air inlet shutoff valve.

The first condition occurs when the operator initiates an emergency shutdown. When the shutdown is recognized, fuel is shut off and the air shutoff solenoid is activated. The second condition is for an engine overspeed.

The customer can activate the air shutoff solenoid by supplying 24 VDC to terminal 54 of the customer connector.

Regardless of the reason for activation, the main power to the ECM must be turned OFF for three seconds in order to reset the engine control.

Note: The air shutoff is optional. A programmable parameter needs to be set with Caterpillar Electronic Technician (ET) in order to enable the air shutoff.

Note: Ensure that the air shutoffs are manually reset after an emergency stop in order to start the engine again.

Illustration 1	g01382553
Typical schematic

Illustration 2	g01381147
P2 ECM connector (P2-13) Drive for the air shutoff solenoid (P2-23) Return for the air shutoff solenoid

Illustration 3	g01381149
Customer connector (Terminal 54) Air shutoff

Illustration 4	g01234146
Location of ECM connectors

Test Step 1. INSPECT ELECTRICAL CONNECTORS AND WIRING

1. Turn the main disconnect switch to the OFF position.

2. Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.

4. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The harness and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. CHECK FOR ACTIVE DIAGNOSTIC CODES

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

2. Turn the main disconnect switch to the ON position.

3. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

   Note: Wait at least 30 seconds in order for any diagnostic codes to become active.

4. Activate the override for the air shutoff system. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

   Note: Wait at least 30 seconds in order for the diagnostic code to become active.

5. Deactivate the override for the air shutoff system.

Expected Result:

No diagnostic codes are active.

Results:

• OK - No diagnostic codes are active.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - A -6 diagnostic code is active at this time. Proceed to Test Step 3.

• Not OK - A -5 diagnostic code is active at this time. Proceed to Test Step 4.

Test Step 3. CREATE AN OPEN AT THE CONNECTOR FOR THE AIR SHUTOFF SOLENOID

1. Disconnect the connector for the air shutoff solenoid.

2. Monitor the active diagnostic code screen on Cat ET. Check for an active diagnostic code for the air shutoff system.

   Note: Wait at least 30 seconds in order for the diagnostic code to become active.

3. Activate the override for the air shutoff system. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

   Note: Wait at least 30 seconds in order for the diagnostic code to become active.

Expected Result:

A -6 diagnostic code was active when the solenoid was connected to the circuit. A -5 diagnostic code is active when the solenoid is removed from the circuit.

Results:

• OK - A -6 diagnostic code was active before disconnecting the connector. A -5 diagnostic code became active after disconnecting the connector. The harness and the ECM are OK. The problem may be in the air shutoff solenoid.

  Repair: Temporarily connect a new air shutoff solenoid to the harness, but do not install the new air shutoff solenoid. Verify that there are no active diagnostic codes for the air shutoff solenoid. If there are no active diagnostic codes for the air shutoff solenoid, permanently install the new air shutoff solenoid. Clear any logged diagnostic codes.

  STOP

• Not OK - A -6 diagnostic code remains active. There is a short between the connector for the air shutoff solenoid and the ECM. Leave the connector for the air shutoff solenoid disconnected. Proceed to Test Step 5.

Test Step 4. CREATE A SHORT AT THE CONNECTOR FOR THE AIR SHUTOFF SOLENOID

1. Disconnect the connector for the air shutoff solenoid.

2. Install a jumper wire between the terminals of the connector for the air shutoff solenoid.

3. Monitor the active diagnostic code screen on Cat ET. Check for an active diagnostic code for the air shutoff system.

   Note: Wait at least 30 seconds in order for the diagnostic code to become active.

4. Activate the override for the air shutoff system. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

   Note: Wait at least 30 seconds in order for the diagnostic code to become active.

Expected Result:

A -6 diagnostic code is now active for the air shutoff system.

Results:

• OK - A -5 diagnostic code was active before creating the short at the connector. A -6 diagnostic code became active after creating the short at the connector. The harness and the ECM are OK. The problem may be in the air shutoff solenoid.

  Repair: Temporarily connect a new air shutoff solenoid to the harness, but do not install the new air shutoff solenoid. Verify that there are no active diagnostic codes for the air shutoff solenoid. If there are no active diagnostic codes for the air shutoff solenoid, permanently install the new air shutoff solenoid. Clear any logged diagnostic codes.

  STOP

• Not OK - The -5 diagnostic code remains active with the jumper in place. The open circuit is between the ECM and the connector for the air shutoff solenoid. Proceed to Test Step 5.

Test Step 5. TEST THE OPERATION OF THE ECM

1. Turn the main disconnect switch to the OFF position.

2. Fabricate jumper wires that can be used to replace the wires in the ECM connector for the air shutoff solenoid. Crimp a connector socket to one end of the jumper wires.

3. Disconnect the J2/P2 ECM connector.

4. Remove the wires for the air shutoff solenoid from the ECM connector.

5. Install the jumper wires into the terminal locations for the air shutoff solenoid at the ECM connector.

6. Connect the ECM connectors.

7. Check the operation of the ECM by creating an open at the ECM:

   1. Hold the loose ends of the jumper wires away from any components in order to create an open circuit condition.

   2. Turn the main disconnect switch to the ON position.

   3. Monitor the active diagnostic code screen on Cat ET. Check for an active diagnostic code for the air shutoff system.

      Note: Wait at least 30 seconds in order for the diagnostic code to become active.

   4. Activate the override for the air shutoff system. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

      Note: Wait at least 30 seconds in order for the diagnostic code to become active.

8. Check the operation of the ECM by creating a short circuit at the ECM:

   1. Create a short between the jumper wires at the ECM connector.

   2. Monitor the active diagnostic code screen on Cat ET. Check for an active diagnostic code for the air shutoff system.

      Note: Wait at least 30 seconds in order for the diagnostic code to become active.

   3. Activate the override for the air shutoff system. Monitor the active diagnostic code screen on Cat ET. Check the air shutoff system for an active diagnostic code.

      Note: Wait at least 30 seconds in order for the diagnostic code to become active.

9. Turn the main disconnect switch to the OFF position.

10. Reconnect all wires to the original configuration.

Expected Result:

A -5 diagnostic code is active when the wires from the air shutoff solenoid are open at the ECM connector. A -6 diagnostic code is active when the wires from the air shutoff solenoid are shorted at the ECM connector.

Results:

• OK - The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the air shutoff solenoid.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

• Not OK - One of the following conditions exists: The -5 diagnostic code is not active when the wire for the prelube relay is disconnected. The -6 diagnostic code is not active when the wire jumper is installed.

  Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.

  STOP