DTC 44

Fig. 048 Code 44 Lean Exhause Indicated:

Fig. 049 Code 44 Lean Exhause Indicated:

CIRCUIT DESCRIPTION:
The ECM supplies a voltage of about 0.45 volt between terminals "B2" and "B23." (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts) The O2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down through about 0.10 volt, if exhaust is lean.
The sensor is like an open circuit and produces no voltage, when it is below about 360 degrees C (600 degrees F). An open sensor circuit, or cold sensor, causes "Open Loop" operation.

TEST DESCRIPTION: Step numbers refer to step numbers on diagnostic chart.

1. Code 44 is set, when the O2 sensor signal voltage on CKT 412:
^ Remains below 0.2 volt for 60 seconds or more;
^ And the system is operating in "Closed Loop."

DIAGNOSTIC AIDS:
Using the "Scan," observe the block learn value at different rpm(s). The "Scan," also, displays the block cells, so the block learn values can be checked in each of the cells, to determine when the Code 44 may have been set. If the conditions for Code 44 exists, the block learn values will be around 150.

^ O2 Sensor Wire. Sensor pigtail may be mispositioned and contacting the exhaust manifold.

^ Check for ground in wire between connector and sensor.

^ 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 44.

^ Fuel Pressure. System will be lean if pressure is too low. It may be necessary to monitor fuel pressure, while driving the car at various road speeds and/or loads to confirm. See Fuel System diagnosis, CHART A-7.

^ Exhaust Leaks. If there is an exhaust leak, the engine can cause outside air to be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can cause a lean condition.

^ If Code 44 intermittent, refer to DIAGNOSIS BY SYMPTOM.