Thanks, amac209 for the good info.
Here is something additional from
http://www.syty.org/old/d&e-code44.html
TEST DESCRIPTION:
Numbers below refer to circled numbers on the diagnostic chart.
This test checks the oxygen sensor's heating element. The heating element resistance should be 3.5 ohms at 20'C (68'F) or 14 ohms at 350'C (562'F).
Code 44 is set when the oxygen (02) sensor signal voltage on CKT 412
remains below .2 volt for 2 minutes and the fuel system is operating in "Closed Loop."
DIAGNOSTIC AIDS:
Using the Tech I diagnostic computer "Scan" tool, observe the block learn values at different rpm and air flow conditions. The "Scan" tool also displays the block cells, so the block learn values can be checked in each of the cells to determine when the Code 44 may have been set. If the conditions for Code 44 or Code 64 exist, the block learn values will be around 150.
O2 Sensor Wire. Sensor pigtail may be mispositioned and contacting the exhaust manifold.
Check for intermittent ground in wire between connector and sensor.
Poor connection at oxygen (02) sensor ground wire.
Lean Injector(s). Perform injector balance test CHART C-2A.
Fuel Contamination. Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a Code 44 or Code 64.
Fuel Pressure. System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the car at various road speeds and/or loads to confirm. Refer to 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 exhaust and past the sensor. Vacuum or crankcase leaks can cause a lean condition.
If the above are OK, it is a faulty oxygen sensor.
Take care, Eggert
