DTC 44 6E3-A-86:
DTC 44 is set when the O2S signal voltage on CKT 412:
Remains below .25 volt for up to 4.5 minutes
The system is operating in "Closed Loop"
Using the Tech 1, observe the long term fuel trim values at different RPM and air flow conditions. The Tech 1 also displays the fuel trim cells, so the long term fuel trim values can be checked in each of the cells to determine when the DTC 44 may have been set, If the conditions for DTC 44 exist, the long term fuel trim values will be around 150 or greater.
Oxygen Sensor Wire Sensor pigtail may be mispositioned and contacting the exhaust manifold.
Check for intermittent ground in wire between connetor and sensor.
Poor PCM to engine block ground.
MAF Sensor A Mass Air Flow (MAF) sensor output that causes the PCM to sense a lower than normal airflow will cause the system to go lean. Disconnect the MAF sensor. If the lean condition id gone, replace the MAF sensor.
Lean Injector(*) Perform injector balance test CHART C-2A
Fuel Contamination Water, even in small amounts, near the in-tank fuel pump inlet can be delivered the the injectors. The water causes a lean exhaust and can set DTC 44.
Fuel Pressure System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at carious road speeds and/or loads to confirm. See "Fuel System Diagnosis," Chart A-7
Exhaust Leaks If there is an exhaust leak, the engine can cause outside air to be pulled into the exhausr past the sensor.
Vacuum or Crankcase Leaks can cause a lean condition and/or possibly a high idle.
If the above are OK, it is a faulty sensor.