Diagnostic Aids
Using ED20 display, observe the block learn values at different RPM and airflow conditions. If the conditions for Code E044 exists, the block learn values will be around 150. Check for the following conditions:
- Oxygen sensor pigtail may be mispositioned and contacting exhaust manifold.
- Check for intermittent ground in wire between connector and sensor.
- A Mass Airflow (MAF) sensor output that causes ECM to sense a lower than normal airflow will cause the system to go lean. Disconnect MAF sensor and if lean condition is eliminated, replace MAF sensor.
- Perform injector balance test, see SYSTEM/COMP TESTS article.
- Water, even in small amounts, near in-tank fuel pump inlet can be delivered to injectors. Water causes a lean exhaust and can set Code E044.
- System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving vehicle at various road speeds and/or loads to confirm problem.
- If there is an exhaust leak, engine can cause outside air to be pulled into exhaust, across the oxygen sensor. Vacuum or crankcase leaks can cause a lean condition.
- If all of the above checks are okay, replace oxygen sensor.