Why do I get a code 44 on my Cadillac which has.

Clearing it does nothing. It will clear itself when the proper repair is done.

Codes never identify bad parts, just failed systems. There are a lot more to the code 44 than the o2 sensor.

When the oxygen sensor is cold (below 200°C), the output voltage will be around 0.5 volts and the ECM will keep the system in open loop operation. When the oxygen sensor is warm (above 200°C), the output voltage will swing between 0.0 and 1.0 volt. When the ECM sees that the oxygen sensor is not at the cold voltage of 0.5 volt and the coolant sensor reads above 85°C, it will send the system into closed loop operation. In closed loop operation, the ECM will meter the fuel into the engine based on the oxygen sensor readings. The low oxygen sensor voltage readings are normally evidence that the air-fuel mixture is lean and the closed loop system is unable to compensate sufficiently due to a failure in some part of engine emission or fuel system. Less likely is the possibility that the oxygen sensor has failed and is giving an incorrectly low reading. However, if this is the case, the closed loop fuel system will be overcompensating and causing rich operation (i.E. Black smoke, fouled spark plugs, poor fuel economy, high HC and CO, etc.) While the O2 sensor is indicating lean.

1. To check the operation of the oxygen sensor circuit, turn the ignition on and display engine data parameter P.0.7. If the "oxygen sensor voltage" reads less than 0.37 volts with the sensor disconnected, check circuit #412 for a short to ground or a short to circuit #413. If circuit #412 is OK, check for a faulty ECM connector of faulty ECM.
2. If the voltage is greater than 0.37 volts, then Jumper the oxygen sensor harness pin (ECM side) to ground and note the voltage reading. If the voltage reading is greater than 0.05 volts, then the ECM is not able to recognize that a fault was artificially created. Check circuits #412 and #413 for an open. If no defect is found, check for a faulty ECM connector or faulty ECM.
3. If the voltage reading is less than 0.05 volts, then the ECM is functioning properly and the harness is OK. Reconnect the oxygen sensor and clear any codes before exiting diagnostics. The diagnosis should now center on determining why the fuel mixture is lean.
4. The ECM compares oxygen sensor signal voltage received on circuit 412 to the ground voltage on circuit 413. If the ECM doesn't have a good ground to the engine on circuit 413, the oxygen sensor can appear falsely high or low. With engine running, use a voltmeter to measure voltage from the oxygen sensor at the exhaust manifold to the ground eyelet for the oxygen sensor (0.8 mm tan wire) at the generator. If the voltage is -0.05 volts to +0.05 volts then the ground voltage is OK. If the voltage is less than -0.05 volts or greater than +0.05 volts, tighten the ground stud at the generator (torque to 28-37 Nm).
A fuel delivery system which is not functioning properly may cause a lean fuel mixture. This malfunction can be caused by fuel pressure less than 9 PSI at the injectors, by defective injectors, etc. Refer to the performance diagnosis chart A-4, "Fuel System Diagnosis, " for additional information.

A loss of EGR will cause a lean fuel mixture. Diagnose EGR system.

If the AIR management system were to send to the exhaust ports at all times, this oxygen would give a lean indication at the oxygen sensor. Diagnose Air Management system.

If the "Oxygen Sensor Test" (chart A-9) indicates that the sensor is OK, then check all connectors, terminals, etc. For an intermittent Code.

Note on Intermittents: If an intermittent Code E44 is being set, manipulate related wiring while observing engine data parameter P.0.7 at part throttle with the engine warm. If the failure is induced, the oxygen sensor reading will change from its normal fluctuating voltage (above 0.60 and below 0.30) to a reading never going above 0.50 volts. This will help to isolate the location of the malfunction.