3512 and 3516 EUI Engines for 784B, 785B, 789B and 793B Off-Highway Trucks Service Engine Lamp Caterpillar


Service Engine Lamp
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System Operation Description:

The service engine lamp is a warning lamp that is located on the operator's panel. The lamp indicates the existence of an "ACTIVE" diagnostic code. The service engine lamp may also be used to read flash codes. If the engine is running and a diagnostic code becomes active, the service engine lamp will illuminate for a minimum of five seconds. The service engine lamp will remain illuminated if a diagnostic code is "ACTIVE". Most diagnostic codes are logged into the memory of the Electronic Control Module (ECM).

Upon start-up, the ECM will perform a self test of the service engine lamp by illuminating the lamp for five seconds. The keyswitch must be in the ON position and the engine must not be running in order to perform the test.

The diagnostic enable switch is used to display "Active" flash codes on the service engine lamp. The diagnostic enable switch is a two-position switch. The switch is located in the operator's cab on the left side of the EMS display module. Refer to the diagnostic procedure Troubleshooting, "Diagnostic Codes" for more information on this feature.

The circuit for the service engine lamp can be tested through the use of the diagnostic test on the AVSpare Electronic Technician (ET). One terminal of the service engine lamp receives 24 VDC from the output of the ECM when the ECM signals the lamp to turn ON. The other terminal of the service engine lamp is connected to the digital return line.

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




Illustration 1g00937137

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 all of the other connectors. 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 2.

  • 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 Service Engine Lamp.

  1. Remove the service engine lamp. Inspect the service engine lamp for damage.

Expected Result:

The service engine lamp should be undamaged.

Results:

  • OK - The service engine lamp is in working condition. Proceed to Test Step 3.

  • Not OK - The service engine lamp is damaged.

    Repair: Replace the service engine lamp.

    Stop.

Test Step 3. Check the Operation of the Service Engine Lamp.

  1. Replace the service engine lamp.

  1. Connect 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 service engine lamp.

  1. Monitor the service engine lamp.

  1. Deactivate the override for the service engine lamp.

Expected Result:

The service engine lamp is not illuminated before the override is activated. The service engine lamp illuminates after the override is activated. The service engine lamp turns OFF after the override is deactivated.

Results:

  • OK - The service engine lamp illuminated during the override. The service engine lamp turned OFF after the override was deactivated.

    Repair: The service engine lamp is operating correctly.

    Stop.

  • Not OK - The service engine lamp did not illuminate. Proceed to Test Step 4.

  • Not OK - The service engine lamp illuminated. The service engine lamp did not turn OFF after the override was deactivated. Proceed to Test Step 5.

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

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Remove the service engine lamp.

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

    • P1-18 and P1-23

    • P1-18 and P1-13

    • P1-18 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 5.

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

    Repair: The wire A430-OR is shorted to ground through one of the three wires in the engine harness. If the short is to wire 229-BK, wire A430-OR 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 5. Check the Harness for a Short to Battery Condition.

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Remove the service engine lamp.

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

    • P1-18 and P1-70

    • P1-18 and P1-65

    • P1-18 and P1-51

    • P1-18 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 6.

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

    Repair: The wire A430-OR is shorted to power through one of the four wires in the engine harness. Locate the short in the engine harness or the machine harness. Repair the connectors or wiring and/or replace the connectors or wiring.

    Stop.

Test Step 6. Check for an Open in the Harness.

  1. Turn the keyswitch to the OFF position.

  1. Disconnect ECM connector J1/P1.

  1. Remove the service engine lamp.

  1. Connect a wire jumper between the two terminals at the base of the service engine lamp.

  1. Measure the resistance between P1-18 and P1-9 at ECM connector P1.

  1. Remove the wire jumper.

Expected Result:

The resistance measures less than 5 Ohms.

Results:

  • OK - The resistance is less than 5 Ohms. Proceed to Test Step 7.

  • 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 service engine lamp. Repair the connectors or wiring and/or replace the connectors or wiring.

    Stop.

Test Step 7. Check the Voltage to the Service Engine Lamp at the ECM.

  1. Turn the keyswitch to the OFF position.

  1. Replace the service engine lamp.

  1. Remove the wire P1-18 (A430-OR) and the digital return wire P1-9 (998-BR) from the ECM connector P1. Install wire jumpers into the sockets for P1-18 and for P1-9.

    Note: If you remove the sensor common from a sensor, an open circuit diagnostic code will be generated for that sensor. Troubleshoot the original code. Delete the logged diagnostic code when you are finished.

  1. Reconnect ECM connector J1/P1.

  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 service engine lamp.

  1. Measure the voltage between the wire jumpers in P1-18 and in P1-9.

  1. Deactivate the override for the service engine lamp.

  1. Turn the keyswitch to the OFF position.

  1. Remove the wire jumpers and replace all wires. Reconnect ECM connector J1/P1.

Expected Result:

The voltage is 24 ± 3 VDC.

Results:

  • OK - The supply voltage is 24 ± 3 VDC. There is a problem in the wiring between the ECM and the service engine lamp.

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

    Stop.

  • Not OK - The supply voltage is not 24 ± 3 VDC.

    Repair: The ECM is not providing the correct voltage to the service engine lamp. Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM" before proceeding further.

    Stop.

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