3512 and 3516 EUI Engines for 784B, 785B, 789B and 793B Off-Highway Trucks Air Filter Restriction Lamp Caterpillar


Air Filter Restriction Lamp
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System Operation Description:

The air filter restriction lamp is a warning lamp that is located on the operator's panel. The lamp indicates that a restriction in the engine air intake and/or the engine air filters has occurred. The Electronic Control Module (ECM) determines that an air restriction is present by comparing the signals from the atmospheric pressure sensor and the turbocharger compressor inlet pressure sensor. If the ECM determines that the signal from either sensor is incorrect or that the difference between the signals of the two sensors is greater than 6.5 kPa (1.0 psi), the ECM will derate engine power. The ECM derates engine power in 2 percent steps. Every 1 kPa (0.15 psi) difference in pressure above 6.5 kPa (1.0 psi) will increase the derate. The maximum engine derate from an air filter restriction is 20 percent. The ECM will output 24 VDC to the air filter restriction lamp. The lamp illuminates.

The air filter restriction is logged as an event into ECM memory. The circuit for the air filter restriction lamp can be tested through the use of the diagnostic test on the AVSpare Electronic Technician (ET).

One terminal of the air filter restriction lamp receives 24 VDC from the output of the ECM when the ECM signals the lamp to turn ON. The other terminal of the air filter restriction 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 1g00930562

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 Air Filter Restriction Lamp.

  1. Remove the air filter restriction lamp. Inspect the air filter restriction lamp for damage.

Expected Result:

The air filter restriction lamp is undamaged.

Results:

  • OK - The air filter restriction lamp is in working condition. Proceed to Test Step 3.

  • Not OK - The air filter restriction lamp is damaged.

    Repair: Replace the air filter restriction lamp.

    Stop.

Test Step 3. Check the Operation of the Air Filter Restriction Lamp.

  1. Replace the air filter restriction 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 the Cat ET.

  1. Activate the override for the air filter restriction lamp.

  1. Monitor the air filter restriction lamp.

  1. Deactivate the override for the air filter restriction lamp.

Expected Result:

The air filter restriction lamp is not illuminated before the override is activated. The air filter restriction lamp illuminates after the override is activated. The air filter restriction lamp turns OFF after the override is deactivated.

Results:

  • OK - The air filter restriction lamp illuminated during the override. The air filter restriction lamp turned OFF after the override was deactivated.

    Repair: The air filter restriction lamp is operating correctly.

    Stop.

  • Not OK - The air filter restriction lamp did not illuminate. Proceed to Test Step 4.

  • Not OK - The air filter restriction lamp illuminated. The air filter restriction 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 air filter restriction lamp.

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

    • P1-3 and P1-23

    • P1-3 and P1-13

    • P1-3 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 430-BU is shorted to ground through one of the three wires in the engine harness. If the short is to wire 229-BK, wire 430-BU 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 air filter restriction lamp.

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

    • P1-3 and P1-70

    • P1-3 and P1-65

    • P1-3 and P1-51

    • P1-3 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 430-BU 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 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 air filter restriction lamp.

  1. Connect a wire jumper between the two terminals at the base of the air filter restriction lamp.

  1. Measure the resistance between P1-3 and P1-9 at ECM connector P1.

  1. Remove the wire jumper.

Expected Result:

The resistanceis 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 connectors between ECM connector P1 and the air filter restriction lamp. Repair the connectors or wiring and/or replace the connectors or wiring.

    Stop.

Test Step 7. Check the Voltage to the Air Filter Restriction Lamp at the ECM.

  1. Turn the keyswitch to the OFF position.

  1. Replace the air filter restriction lamp.

  1. Remove the wire P1-3 (430-BU) and wire P1-9 (998-BR) from the ECM connector P1. Install wire jumpers into the sockets for P1-3 and for P1-9.

    Note: The digital return will no longer be connected to the other sensors and switches. Additional diagnostic codes will be generated from the ECM. Clear the codes after you complete this test.

  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 air filter restriction lamp.

  1. Measure the voltage between the wire jumpers in P1-3 and in P1-9.

  1. Deactivate the override for the air filter restriction 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 air filter restriction 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 air filter restriction lamp. Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM" before proceeding further.

    Stop.

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