Diagnostic Aids
The Code EO44 or lean exhaust is most likely caused by one of the following:
- Fuel Pressure. System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the vehicle at various road speeds and/or loads to confirm.
- Fuel Contamination. Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injector. The water causes a lean exhaust and can set a Code EO44.
- Sensor Wire. Sensor pigtail may be mispositioned and contacting the exhaust manifold.
- MAF Sensor. An output that causes the ECM to sense a lower than normal manifold airflow will cause the system to go lean.
- If the above are okay, and the instructions at the top of the chart will still set a Code EO44, or "SERVICE ENGINE SOON" light is off more than on, or flashing "open loop", it is a faulty oxygen sensor.