3512B Marine Auxiliary Engine Caterpillar

The digital sensor supply provides power to all digital sensors. This engine has more than one Electronic Control Module (ECM). Be sure that you perform the test procedure for the correct ECM. The MID for the primary ECM is 036. The MID for the secondary ECM is 047.

The digital sensor supply is output short circuit protected. A short circuit to the Battery should not cause permanent damage to the circuit inside the ECM. The digital sensors are NOT protected from overvoltage.

Illustration 1	g00858363
Primary ECM

Illustration 2	g00849957
Secondary ECM

Test Step 1. Check for Connector Damage.

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

2. Turn the breaker at the battery to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Perform the diagnostic functional testTroubleshooting, "Inspecting Electrical Connectors".

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

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

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

7. 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, abrasion or 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 for a Short Circuit in the Wiring Harness.

1. Disconnect J1/P1. Disconnect all of the digital sensors.

2. Measure the resistance between the digital supply P1-35 (A700-OR) and the digital return P1-29 (998-BR) .

3. Measure the resistance between the digital supply P1-35 (A700-OR) and engine ground.

4. Measure the resistance between the digital return P1-29 (998-BR) and the engine ground.

5. Reconnect J1/P1. Reconnect J2/P2.

Expected Result:

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

Results:

• OK - The resistance is greater than 20,000 Ohms for each measurement. Proceed to test step 3.

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

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify the repair by rechecking for shorts in the harness.

  Stop.

Test Step 3. Check the Digital Supply Voltage at the ECM.

1. Install a Breakout T at the Primary ECM connector J1/P1.

2. Remove the wires from P1-35 and P1-29 at the Breakout T.

   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 breaker at the battery to the ON position.

4. Turn the ECS to the STOP position. The engine should be OFF.

5. Measure the voltage between the digital sensor supply P1-35 and the digital sensor return P1-29 at the Breakout T.

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

7. Remove the Breakout T and reconnect ECM connector J1/P1.

Expected Result:

The supply voltage should be 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. The digital sensor supply is producing the correct voltage. Proceed to test step 4.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC.

  Repair: Replace the ECM. Perform the diagnostic functional test Troubleshooting, "Electrical Power Supply".

  Stop.

Test Step 4. Check the Digital Sensor Supply Voltage at the Sensor Connector.

1. Turn the ECS to the STOP position. The engine should be OFF.

2. Measure the digital sensor supply voltage between the digital supply terminal-A (A700-OR) and the digital return terminal-B (998-BR) of all the digital sensors.

   Note: If the sensor is disconnected from the harness, an open circuit diagnostic code will be generated for that sensor. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

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

Expected Result:

The supply voltage should be 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. The supply voltage is present at all of the digital sensor connectors. Proceed to test step 5.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC. There is an open circuit in the harness or connectors.

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

  Stop.

Test Step 5. Check the Digital Sensors for Short Circuits.

1. Install a Breakout T at the Primary ECM connector J1/P1.

2. Turn the ECS to the STOP position. The engine should be OFF.

3. Connect one digital sensor at a time.

   Note: If the sensor is disconnected from the harness, an open circuit diagnostic code will be generated for that sensor. Troubleshoot the original code. Delete the logged diagnostic codes when you are finished.

4. Check the digital sensor supply voltage between the digital sensor supply P1-35 and the digital sensor return P1-29 at the Breakout T. Repeat this step with all of the digital sensors.

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

6. Remove the Breakout T and reconnect ECM connector J1/P1.

Expected Result:

The supply voltage should be 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage should be 8.0 ± 0.4 VDC. The digital sensor supply is OK. The harness is OK. Stop.

• Not OK - The sensor may be internally shorted.

  Repair: Temporarily connect a new sensor. Verify that the new sensor solves the problem before permanently installing the new sensor.

  Stop.

• Intermittent - The problem is intermittent.

  Repair: Perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.