3512 and 3516 EUI Engines for 784B, 785B, 789B and 793B Off-Highway Trucks ECM Output Circuit (Engine Oil Pressure Lamp) Caterpillar


ECM Output Circuit (Engine Oil Pressure Lamp)
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System Operation Description:

The engine monitoring system's engine oil pressure lamp indicates that a low engine oil pressure condition exists. The engine oil pressure lamp is located on the operator's panel. The engine oil pressure lamp is turned ON when the engine oil pressure falls below the minimum engine oil pressure that is defined by a map of oil pressure versus engine rpm. The map is stored in the personality module of the Electronic Control Module (ECM). The engine oil pressure lamp also illuminates when the diagnostic codes 100-03 and 100-04 are active.

The ECM turns ON the input for the engine oil pressure lamp when a problem with the engine oil pressure is detected. The input for the engine oil pressure lamp is a sinking driver. When the input is turned ON, current flow in the circuit illuminates the engine oil pressure lamp. The circuit for the engine oil pressure lamp can be tested through the use of the diagnostic test on the AVSpare Electronic Technician (ET). The engine oil pressure lamp is used to replace the signal from the oil pressure switch on engines that were equipped with mechanical unit injectors (MUI).

Note: This feature is not present on machines that are equipped with the Vital Information Management System (VIMS).




Illustration 1g00931750

Test Step 1. Check for Connector Damage.

  1. Turn the keyswitch to the OFF position.

  1. Thoroughly inspect the ECM connector J1/P1. Thoroughly inspect the machine connector J2/P2. Inspect the operator monitor panel plug. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.

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

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

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

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

Expected Result:

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

Results:

  • OK - The connectors and wiring are okay. Proceed to Test Step 3.

  • Not OK - The connectors and/or wiring are not okay.

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

    Stop.

Test Step 2. Check the Operation of the Engine Oil Pressure Lamp.

  1. Connect the Cat ET to the ECM through the J31 cab service tool connector.

  1. Turn the keyswitch to the ON position. The engine should be off.

  1. Access the diagnostic test on Cat ET.

  1. Activate the override for the low oil pressure lamp.

  1. Monitor the engine oil pressure lamp.

  1. Deactivate the override for the low oil pressure lamp.

Expected Result:

The engine oil pressure lamp is not ON before the override is activated. The engine oil pressure lamp is ON after the override is activated. The engine oil pressure lamp turns OFF after the override is deactivated.

Results:

  • OK - The engine oil pressure lamp was ON during the override. The engine oil pressure lamp turned OFF after the override was deactivated.

    Repair: The engine oil pressure lamp is operating correctly.

    Stop.

  • Not OK - The engine oil pressure lamp did not turn ON. Proceed to Test Step 3.

  • Not OK - The engine oil pressure lamp turned ON. The engine oil pressure lamp did not turn OFF after the override was deactivated. Proceed to Test Step 4.

Test Step 3. Check the Harness for a Short to Ground Condition.

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Disconnect the operator monitor panel plug.

  1. Measure the resistance between the following pins on the ECM connector:

    • P1-63 and P1-23

    • P1-63 and P1-13

    • P1-63 and P1-9

Expected Result:

The resistance is 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 4.

  • Not OK - The resistance is less than 20,000 Ohms for one of the measurements.

    Repair: The wire 405-GY is shorted to ground through one of the three wires in the engine harness. If the short is to wire 229-BK, wire 405-GY could be shorted to the engine block or to the chassis. If the short is not to wire 229-BK, locate the short in the engine harness or locate the short in the machine harness. Repair the connectors or wiring and/or replace the connectors or wiring.

    Stop.

Test Step 4. Check the Harness for a Short to Battery Condition.

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Disconnect the operator monitor panel plug.

  1. Measure the resistance between the following pins on the ECM connector:

    • P1-63 and P1-70

    • P1-63 and P1-65

    • P1-63 and P1-51

    • P1-63 and P1-37

Expected Result:

The resistance is 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 5.

  • Not OK - The resistance is less than 20,000 Ohms for one of the measurements.

    Repair: The wire 405-GY is shorted to power through one of the four wires in the engine harness. Locate the short in the engine harness or in the machine harness. Repair the connectors or wiring and/or replace the connectors or wiring.

    Stop.

Test Step 5. Check for an Open in the Harness.

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Disconnect the operator monitor panel plug.

  1. Connect a wire jumper between wire P1-63 (405-GY) and wire P1-2 (201-BK) at the operator monitor panel plug.

  1. Measure the resistance between P1-63 and P1-13 at ECM connector P1.

  1. Remove the wire jumper.

  1. Reconnect all connectors.

Expected Result:

The resistance measures less than 5 Ohms.

Results:

  • OK - The resistance is less than 5 Ohms. Proceed to Test Step 6.

  • Not OK - The resistance is more than 5 Ohms.

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

    Stop.

Test Step 6. Check the Voltage to the Operator Monitor Panel Plug for the Engine Oil Pressure Lamp.

  1. Turn the keyswitch to the OFF position.

  1. Turn the keyswitch to the ON position. The engine should be off.

  1. Measure the voltage between P1-63 and P1-13 at ECM connector J1/P1.

  1. Access the diagnostic test on the Cat ET.

  1. Activate the override for the low oil pressure lamp.

  1. Measure the voltage between P1-35 and P1-13 at ECM connector J1/P1.

  1. Deactivate the override for the low oil pressure lamp.

  1. Turn the keyswitch to the OFF position.

Expected Result:

The voltage is 7.5 ± 0.5 VDC when the override is OFF. The voltage is 0.5 ± 0.5 VDC when the override is ON.

Results:

  • OK - The voltage was 7.5 ± 0.5 VDC when the override was OFF. The voltage was 0.5 ± 0.5 VDC when the override was ON. There is a problem in the wiring between the ECM and the operator monitor panel plug.

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

    Stop.

  • Not OK - The voltage was not 7.5 ± 0.5 VDC when the override was OFF. The voltage was not 0.5 ± 0.5 VDC when the override was ON.

    Repair: The sinking driver on the ECM is not working properly. Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM" before proceeding further.

    Stop.

Information System:

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