Diagnostic Aids

Using Scan tester, observe block learn value at different RPM. Scan tester also displays block cells, so block learn values can be checked in each of the cells, to determine when Code 44 set. If conditions for Code 44 exist, block learn values will be approximately 150.

Scan Tester:

• Ensure oxygen sensor pigtail is not contacting exhaust manifold.
• Check for ground in wire between connector and oxygen sensor.
• Water delivered to fuel injectors can cause a lean mixture. This can set a Code 44.
• Fuel system will be lean if pressure is too low. Monitor fuel pressure while driving at various road speeds and/or loads to confirm a problem (if necessary).
• If exhaust leak is present, outside air can be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can also cause a lean condition.
• If heater portion of oxygen sensor fails, this may set a Code 44 or 45. See appropriate I - EFI SYS/COMP TESTS article in the ENGINE PERFORMANCE Section

For intermittent inspection, see INTERMITTENTS in H - EFI TESTS W/O CODES article in the ENGINE PERFORMANCE Section.

Fig 1: Code 44 Circuit Diagram-O2 Sensor Ckt. (Turbo)

Courtesy of ISUZU MOTOR CO.

Fig 2: Code 44 Flow Chart-O2 Sensor Ckt. (Turbo)

Courtesy of ISUZU MOTOR CO.