3512B Marine Auxiliary Engine Caterpillar

The engine's Primary Electronic Control Module (ECM) receives four input signals from the Engine Control Switch (ECS). The input signals allow the control to determine the mode of operation. The ECS can operate in four modes: OFF/RESET, MAN/START, COOLDOWN/STOP and AUTO.

When the ECS is set to the OFF/RESET position, the START/RUN/STOP INPUT and the AUTO input are open. The ECM is not powered. Engine operation will stop when the ECS is switched to this position.

When the ECS is set to the AUTO position, the START/RUN/STOP INPUT is low and the AUTO input is low. The ECM is powered.

When the ECS is set to the MAN/START position, The START/RUN/STOP INPUT is low and the ECS in AUTO input is open. The ECM will begin the engine start sequence.

When the ECS is set to the COOLDOWN/STOP position, the START/RUN/STOP INPUT and the ECS in AUTO input are open. After the engine cooldown, the ECM will shut down the engine.

If the signals from the START/RUN/STOP INPUT are opposite, the ECM determines that one of the signals is faulty. The ECM ignores the signals until power is cycled to the ECM.

If this occurs, the engine must be cranked manually. Use the Manual Crank Switch which is located inside the Electronic Instrument Panel. When the engine is shut down, the ECS must be placed in the OFF/RESET position. This will disconnect power to the ECM. A CID-FMI will be active until the ECM is powered down. The status for the Ignition Switch will display "ABNORMAL DATA" until power to the ECM is cycled.

Illustration 1	g00808673
Typical schematic

Note: The Engine Control Switch (ECS) is mounted within an instrument panel that is located on the right side of the engine. The ECS is locked into the AUTO position with a pin. The pin must be removed in order to perform this test. After performing this test, ensure that the ECS is placed in the AUTO position and that the locking pin has been reinstalled.

Test Step 1. Check for Connector Damage

1. Turn the circuit breaker for the battery to the OFF position.

2. Turn the ECS to the OFF/RESET position.

3. Disconnect the main power.

4. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

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

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

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

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

Expected Result:

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

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 Status of the Switch in the STOP position.

1. Turn the circuit breaker for the battery to the ON position.

2. Turn the circuit breaker for the mag relays of the starting motor system to the OFF position.

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

4. Turn the ECS to the STOP position.

5. Observe the status for the ignition switch on the Cat ET.

Expected Result:

The status for the ignition switch should read "STOP".

Results:

• OK - The status for the ignition switch reads "STOP". Proceed to test step 3.

• Not OK - The status for the ignition switch does not display "STOP". Proceed to test step 5.

Test Step 3. Check the Status of the Switch in the START position.

1. Turn the ECS to the START position.

2. Observe the status for the ignition switch on the Cat ET.

Expected Result:

The status for the ignition switch should read "RUN".

Results:

• OK - The status for the ignition switch reads "RUN". Proceed to test step 4.

• Not OK - The status of the ignition switch does not display "RUN". Proceed to test step 5.

Test Step 4. Check the Status of the Switch in the AUTO position.

1. Turn the ECS to the AUTO position.

2. Observe the status for the ignition switch on the Cat ET.

Expected Result:

The status for the ignition switch should read "AUTO".

Results:

• OK - The status for the ignition switch reads "AUTO".

  Repair: The ECM is receiving the correct input from the ECS. The ECS is working correctly.

  Stop.

• Ignition Switch Not OK - The status for the ignition switch does not display "AUTO". Proceed to test step 6.

Test Step 5. Check the Inputs to the ECM for the STOP position and the START position.

1. Turn the ECS to the OFF/RESET position.

2. Disconnect the primary ECM connector P1. Remove wires P1-14, P1-8 and P1-29. Install a wire jumper with a socket on both ends into P1-14, P1-8 and 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.

3. Turn the ECS to the STOP position.

4. Observe the status for the ignition switch on the Cat ET.

5. Connect the jumper wire between the wire jumpers that are in P1-14 and P1-8 to P1-29.

6. Observe the status for the ignition switch on the Cat ET.

7. Turn the ECS to the OFF/RESET position.

Expected Result:

The status for the ignition switch should display "STOP" when the wire jumper is not installed. The status for the ignition switch should display "RUN" while the wire jumper is installed.

Results:

• OK - The status for the ignition switch displays the proper states. The problem is not with the ECM. Proceed to test step 6.

• Not OK - The status for the ignition switch does not show the correct states.

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

  Stop.

Test Step 6. Check the Input to the ECM for the AUTO position.

1. Turn the ECS to the OFF/RESET position.

2. Disconnect the primary ECM connector P1. Remove wire P1-13. Install a wire jumper with a socket on both ends into P1-13.

3. Connect the wire jumper between the wires from P1-14, P1-8, P1-13 and P1-29.

4. Turn the ECS to the STOP position.

5. Observe the status for the ignition switch on the Cat ET.

6. Turn the ECS to the OFF/RESET position. Remove all wire jumpers. Replace all wires and reconnect ECM connector P1/J1.

Expected Result:

The status for the ignition switch should display "AUTO" while the wire jumper is installed.

Results:

• OK - The status for the ignition switch displays the proper state. The problem is not with the ECM. Proceed to test step 7.

• Not OK - The status for the ignition switch does not show the correct states.

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

  Stop.

Test Step 7. Check the Switch and the Wiring with the ECS in the STOP position.

1. Turn the ECS to the OFF/RESET position.

2. Turn the circuit breaker for the battery to the OFF position.

3. Disconnect the primary ECM connector P1.

4. Turn the ECS to the STOP position.

5. Measure the following resistances at ECM connector P1.

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

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

Expected Result:

The resistance should be greater than 20,000 Ohms.

Results:

• OK - The resistance is greater than 20,000 Ohms. The ECS appears to be functioning properly. Proceed to test step 8.

• Not OK - The resistance is less than 20,000 Ohms. There is a short circuit in the ECS and/or the wiring between the ECS and the ECM.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. If the wiring is okay, replace the ECS.

  Stop.

Test Step 8. Check the Switch and the Wiring with the ECS in the START position.

1. Turn the circuit breaker for the battery to the OFF position.

2. Turn the ECS to the START position.

3. Measure the following resistances at ECM connector P1.

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

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

Expected Result:

The resistance should read less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms. Proceed to test step 9.

• Not OK - The resistance is greater than 10 Ohms. There is an open circuit in the ECS and/or the wiring between the ECS and the ECM.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. If the wiring is okay, replace the ECS.

  Stop.

Test Step 9. Check the Switch and the Wiring with the ECS in the AUTO position.

1. Turn the circuit breaker for the battery to the OFF position.

2. Turn the ECS to the AUTO position.

3. Measure the following resistances at ECM connector P1.

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

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

   3. Measure the resistance between P1-29 and the P1-13.

Expected Result:

The resistance should read less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms.

  Repair: The ECS and the wiring are functioning correctly. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The resistance is greater than 10 Ohms. There is an open circuit in the ECS and/or the wiring between the ECS and the ECM.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. If the wiring is okay replace the ECS.

  Stop.