Using scan tester, observe block learn value at different RPMs. 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.

Ensure O2 sensor pigtail is not contacting exhaust manifold.
Check for ground in wire between connector and O2 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 O2 sensor fails, this may set a Code 44 or 45. See appropriate SYSTEM & COMPONENT TESTING article.

For intermittent inspection, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - FUEL INJECTION article.

Fig 1: Code 44 - Schematic (DOHC)

Courtesy of ISUZU MOTOR CO.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Diagnostic Aids

Use the Manual With the Right Hardware

When to See a Mechanic

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