DTC 44

Code Chart 44:

Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:
The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "D10" and "D11." (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.)

When the 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.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 44 is set when the O2S signal voltage on CKT 412 remains below .28 V (280 mV) volt for 25 seconds or longer.

DIAGNOSTIC AIDS:
Using the scan tool, observe the long term fuel trim value at different engine speeds If the conditions for DTC 44 exist, the long term fuel trim values will be around 160 or higher

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.

^ 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 O2S may set an intermittent DTC 44.