HARNESS AS-MONITOR 2578837 - Caterpillar

Probable Causes
Incorrect calibration of the sensors for exhaust emissions
Incorrect air/fuel ratio
Air inlet restriction
Plugged aftercoolerRecommended Actions
Note: If the symptom only occurs under certain operating conditions (high idle, engine operating temperature, etc), test the engine under the conditions. Troubleshooting the symptom under other conditions can give misleading results.Incorrect Calibration of the Sensors for Exhaust Emissions
Incorrect calibration of the oxygen sensor (if equipped) or the NOX sensor may be the cause of unstable engine operation or a loss of engine power. Check the calibration of the sensors for the exhaust emissions.If the engine is equipped with an oxygen sensor, refer to Troubleshooting, "Oxygen Sensor - Calibrate".If the engine is equipped with a NOX sensor, refer to Troubleshooting, "Nitrogen Oxide Sensor - Calibrate".Incorrect Air/Fuel Ratio (Oxygen Feedback)
An air/fuel mixture that is too rich will cause detonation. Verify that the exhaust emissions are correct. Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust (Oxygen Feedback)".A change in the fuel energy content will change the air/fuel ratio. Obtain a fuel analysis.The fuel supply pressure must be adequate and stable. Ensure that the fuel metering valve is operating correctly.Incorrect Air/Fuel Ratio (NOX Feedback)
An air/fuel mixture that is too rich will cause detonation. Verify that the exhaust emissions are correct. Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - Adjust (NOX Feedback)".A change in the fuel energy content will change the air/fuel ratio. Obtain a fuel analysis.The fuel supply pressure must be adequate and stable. Make sure that the fuel metering valve is operating correctly.Air Inlet Restriction
The maximum allowable air inlet restriction is 3.75 kPa (15 inches of H2O). If the indication is higher than the maximum permissible restriction, clean the filter element or install a new filter element. Check the restriction again. If the restriction remains too high, inspect the air inlet piping for obstructions.For more information, refer to Systems Operation/Testing and Adjusting, "Restriction of Air Inlet and Exhaust".Aftercooler
A plugged aftercooler will adversely affect engine power. Check the aftercooler differential pressure. Refer to Systems Operation/Testing and Adjusting, "Restriction of Air Inlet and Exhaust". Clean the aftercooler, if necessary. Refer to the engine's Operation and Maintenance Manual.