Powertrain Controls - ECM/PCM

Code Chart 44:

Oxygen Sensor Wiring Circuit:

Circuit Description:
The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "C7" and "C8". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.)

When the Oxygen Sensor (O2S) reaches operating temperature, it varies this voltage from about .1 volt (exhaust is lean) to about .9 volt (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.

DTC 44 Will Set When:
^ The O2S signal voltage on CKT 412 remains below .35 volt.
^ Engine run time after start is 2 minutes or more.
^ Throttle angle is greater than 5%.
^ These conditions exist for 25 seconds or more.

Action Taken (ECM will default to): Malfunction Indicator Lamp (MIL) illuminates.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if DTC 44 is the result of a hard failure or an intermittent condition.

Diagnostic Aids: Using the scan tool, observe the long term fuel trim value at different engine speeds. 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 exists, the long term fuel trim values will probably be around 150 or higher.

Check the following possible causes:
^ Oxygen Sensor (O2S) Wire - Sensor pigtail may be routed incorrectly 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 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. Refer to CHART A-7. 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, refer to "Diagnosis By Symptom." - Intermittent Malfunctions
^ A cracked or otherwise damaged O2S may set an intermittent DTC 44.