Diagnostic Aids
Using a scan tester, observe long term fuel trim value at different RPM. Scan tester also displays long term fuel trim cells, so long term fuel trim values in each cell can be checked to determine when Code 44 may have been set. If conditions for Code 44 exist, long term fuel trim values will be about 150.
Ensure O2 sensor pigtail is not mispositioned and contacting exhaust manifold. Check for ground in wire between connector and sensor. Check for fuel contamination. Water can cause a lean exhaust and can set Code 44. Check fuel pressure. System will be lean if fuel pressure is low. Check for exhaust leaks. If there is an exhaust leak, engine pulls outside air into exhaust and past O2 sensor. Vacuum or crankcase leaks can also cause a lean condition. If wrong fuel injectors are installed in vehicle, this will also cause a lean condition. If code is intermittent, see TESTS W/O CODES article in this section.
Check O2 sensor wire for induced voltage. Disconnect O2 sensor signal wire at sensor and ECM. Using DVOM, measure voltage on wire with engine running. If .3 volt (300 mV) or more is present, check signal wire shield and/or reroute signal wire away from any high voltage sources (ignition wires, battery cables, alternator "B" circuit, etc.).