ROD A 3Y2779 - Caterpillar

Probable Causes
Oxygen sensor
Inlet air temperature sensor
Inlet air pressure sensorRecommended Repairs
Oxygen Sensor
An oxygen sensor that is not calibrated will adversely affect the air/fuel ratio.Calibrate the oxygen sensor. Refer to Troubleshooting, "Oxygen Sensor - Calibrate".Inlet Air Temperature Sensor
An inlet air temperature sensor that is producing an incorrect signal will have an adverse effect on the air/fuel ratio. Verify that the sensor is producing the correct signal. Measure the temperature of the inlet air with a thermometer. Compare the reading with the value that is displayed on the Caterpillar Electronic Technician (ET). Replace the sensor, if necessary.Inlet Air Pressure Sensor
An inlet air pressure sensor that is producing an incorrect signal will have an adverse effect on the air/fuel ratio. Verify that the sensor is producing the correct signal. Measure the pressure of the inlet air with a gauge. Compare the reading with the value that is displayed on Cat ET. Replace the sensor, if necessary.