Powertrain Controls - ECM/PCM

DTC 44 Left (Bank 2) Oxygen Sensor:

Left Bank Oxygen Sensor Circuit Wiring Diagram:

Circuit Description:

The Engine Control Module (ECM) supplies a voltage of about 0.45 volt between terminals "B21" and "B20". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.)

When the O2 Sensor reaches operating temperature, it varies this voltage from about 100 millivolts (exhaust is lean) to about 900 millivolts (exhaust is rich).

The sensor is like an open circuit and produces no voltage when it is below 316°C (600°F). An open sensor circuit, or cold sensor, causes "Open Loop" operation.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 44 is set when the 02 sensor signal voltage on CKT 1665 remains below 0.25 volt (250 mV) for 60 seconds or more.

Diagnostic Aids:

Using the scan tool, observe the long term fuel trim at different RPM and air flow conditions. The scan tool also displays the fuel trim cells, so the long term fuel trim values can be checked in each of the cells to determine when the DTC 44 may have been set. If the conditions for DTC 44 exist, the long term fuel trim values will be around 150.

Check the following possible causes:

^ Oxygen Sensor Wire - Sensor pigtail may be mis-positioned and contacting the exhaust manifold. Check for ground in wire between connector and sensor.

^ Lean Injector(s). Perform injector balance test Testing and Inspection

^ Fuel Contamination - Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a DTC 44.

^ Fuel Pressure - System will be lean if fuel 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. Related Tests, Information and Procedures

^ 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 DTC 44 is intermittent, Testing and Inspection

^ A cracked or otherwise damaged 02 Sensor may set an intermittent DTC 44.