3512B Petroleum Engines with the ADEM 2 Electronic Control Module Caterpillar

The Electronic Control Module (ECM) receives two input signals from the Start/Run/Stop switch. The two input signals should have the same logic level. If two different signals are detected during the powerup, the ECM will determine that one of the signals is incorrect. The duplication of the signals permits the ECM to know if there is a problem in the wiring.

When both of the input signals are high or open, the ECM assumes that the Start/Run/Stop switch is in the STOP position. When both of the input signals are low or shorted to the − Battery terminal, the ECM assumes that the Start/Run/Stop switch is in the START position. After the Start/Run/Stop switch is turned to the START position, the ECM will initiate the starting sequence. The ECM will energize the prelube system if the prelube system is available and activated. After the prelube cycle is completed the ECM will energize the starting solenoids for the starting motors. If both of the signals go high or open while the engine is running, the engine will stop.

If the engine is running and one of the inputs from the Start/Run/Stop switch changes states, the ECM will ignore the inputs from the Start/Run/Stop switch until power is cycled to the ECM. If this occurs, you must use the Emergency Stop switch or you must disconnect the power to the ECM in order to shut down the engine.

If the inputs from the Start/Run/Stop switch are in opposite states at the beginning of a crank cycle, the ECM will not initiate the crank cycle. If this condition occurs, the engine may be started by using the Manual Crank switch. If you start the engine with the Manual Crank switch, you must use the Emergency Stop switch or you must disconnect the power to the ECM in order to shut down the engine. A diagnostic code will be logged and a diagnostic code will be active for this problem. The diagnostic code for this problem will be active until the ECM is powered down.

Illustration 1	g00892095

Test Step 1. Check for Connector Damage.

1. Disconnect the main power.

2. Thoroughly inspect the ECM connector J1/P1. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

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

4. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

5. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

6. Check the harness and the wiring for abrasion and pinch points.

Expected Result:

The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.

Results:

• OK - The connectors and wiring are okay. Proceed to test step 2.

• Not OK - The connectors and/or wiring need repair.

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

  STOP

Test Step 2. Check the Switch Status on the Caterpillar Electronic Technician (ET).

1. Connect the main power.

2. Start the Cat ET.

3. Turn the Start/Run/Stop Switch to the STOP position.

4. Monitor the parameter for the switch on the Cat ET.

5. Turn the Start/Run/Stop Switch to the START position.

6. Monitor the parameter for the switch on the Cat ET.

7. Turn the Start/Run/Stop Switch to the STOP position.

Expected Result:

The parameter for the switch should read "OFF" when the Start/Run/Stop Switch is turned to the STOP position. The parameter for the switch should read "ON" when the Start/Run/Stop Switch is turned to the START position.

Results:

• OK - The parameter for the switch is correct in both the STOP and START positions.

  Repair: The switch is functioning correctly. Reset the system and check for any active diagnostic codes.

  STOP

• Not OK - The parameter for the switch is not correct in either the STOP or the START positions. Proceed to test step 3.

Test Step 3. Check the Wiring for an Open Circuit.

1. Disconnect the main power.

2. Disconnect the ECM connector J1/P1.

3. Note the location of the wires on the Start/Run/Stop Switch. Remove the wires from the Start/Run/Stop Switch.

4. Install a wire jumper between the wire 998-BR and the wires F716-WH and F717-YL at the Start/Run/Stop Switch.

5. Measure the resistance between P1-29 and P1-8 at ECM connector P1.

6. Measure the resistance between P1-29 and P1-14 at ECM connector P1.

7. Reconnect all connectors and all wiring.

Expected Result:

The resistance should be less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms for each measurement. Proceed to test step 4.

• Not OK - The resistance is more than 10 Ohms.

  Repair: There is excessive resistance or an open in the wiring between the switch and the ECM connector P1. Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 4. Check The Wiring for a Short Circuit.

1. Disconnect the main power.

2. Disconnect the ECM connector J1/P1.

3. Note the location of the wires on the Start/Run/Stop Switch. Remove the wires from the Start/Run/Stop Switch.

4. Measure the resistance between P1-29 and P1-8.

5. Measure the resistance between P1-29 and P1-14.

6. Measure the resistance between P1-8 and P1-14.

7. Measure the resistance between P1-8 and engine ground.

8. Reconnect all connectors and all wiring.

Expected Result:

The resistance should be greater than 20,000 Ohms for each measurement.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to test step 5.

• Not OK - The resistance is less than 20,000 Ohms.

  Repair: The wire(s) with the low resistance reading to ground is damaged. Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 5. Check the Start/Run/Stop Switch.

1. Disconnect the main power.

2. Disconnect the ECM connector J1/P1.

3. Note the location of the wires on the Start/Run/Stop Switch. Remove the wires from the Start/Run/Stop Switch.

4. Ensure that the Start/Run/Stop Switch is not activated.

5. Measure the resistance between the terminals on the Start/Run/Stop Switch.

6. Activate the Start/Run/Stop Switch.

7. Measure the resistance between the terminals on the Start/Run/Stop Switch.

8. Reconnect all connectors and all wiring.

Expected Result:

The resistance should be greater than 20,000 Ohms when the Start/Run/Stop Switch is in the STOP position. The resistance should be less than 10 Ohms when the Start/Run/Stop Switch is in the START position.

Results:

• OK - The resistance measurements are correct. Proceed to test step 6.

• Not OK - The resistance measurements are not correct.

  Repair: Replace the Start/Run/Stop Switch. Reconnect all connectors and wiring. Verify that the problem is no longer present.

  STOP

Test Step 6. Check the ECM.

1. Disconnect the main power.

2. Disconnect ECM connector J1/P1.

3. Remove wire F716-WH from the ECM connector P1-08. Install a wire jumper into the socket for P1-08.

4. Remove wire F717-YL from the ECM connector P1-14. Install a wire jumper into the socket for P1-14.

5. Remove wire 998-BR from the ECM connector P1-29. Install a wire jumper into the socket for P1-29.

   Note: If you remove the sensor common from the ECM an open circuit diagnostic code will be generated for all sensors that use the sensor common. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

6. Reconnect ECM connector J1/P1.

7. Connect the main power.

8. Observe the parameter for the switch on the Cat ET.

9. Disconnect the main power.

10. Short the wire jumpers from P1-08, P1-14 and P1-29 together.

11. Connect the main power.

12. Observe the parameter for the switch on the Cat ET.

13. Disconnect the main power. Remove the wire jumpers. Reinstall all wires, and reconnect J1/P1.

Expected Result:

The switch status should read "ON" when the jumpers are shorted together. The switch status should read "OFF" when the jumpers are not shorted together.

Results:

• OK - The parameter for the Start/Run/Stop Switch displays the proper state. The problem is not with the ECM.

  Repair: The ECM is receiving the correct signal input. The wiring is okay. The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - The parameter for the Start/Run/Stop Switch does not show the correct state.

  Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  STOP