Diagnostic Aids

Using Scan tester, observe the block learn value at different engine RPM. If the conditions for Code 44 exist, block learn value will be 150 or higher.

• O2 sensor wire pigtail may be mispositioned and contacting exhaust manifold.
• Check for ground in wire between connector and sensor.
• Even a small amount of water contamination near the in-tank fuel pump inlet can be delivered to the injector, causing a lean exhaust and setting Code 44.
• Low fuel pressure can cause a lean exhaust. It may be necessary to monitor fuel pressure while driving car at various road speeds and engine loads.
• Exhaust leaks ahead of O2 sensor can dilute exhaust gases, causing a false lean signal and Code 44. If Code 44 is intermittent, see INTERMITTENTS in TESTS W/O CODES article in this section.

Fig 1: Code 44 Flow Chart, O2 Sensor Ckt., Lean Exhaust

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 44 Schematic, O2 Sensor Ckt., Lean Exhaust

Courtesy of GENERAL MOTORS CORP.