DTC 44

Fig. 048 - WIRING DIAGRAM for Code 44 Lean Exhaust Indication. VIN 3, VIN 9:

CODE 44, LEAN EXHAUST INDICATION

The ECM supplies a voltage of about .45 volt between terminals "D6" and "D7". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volts.) The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about .10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 360°C (600°F). An open sensor circuit or cold sensor causes open loop operation.
Code 44 is set when the O2 sensor signal voltage at the ECM connector terminal D7:
a. Remains below .2 volt for 1 minute or more;
b. Time since engine start is 2 minutes or longer.

Fig. 047 - Chart - Code 44 Lean Exhaust Indication:

1. Grounding the diagnostic terminal with the engine running, enables the "Field Service Mode" and allows the ECM to confirm either open or closed loop operation using the "SERVICE ENGINE SOON" light.
2. A light out or "Open Loop" indicates the fault is present. Disconnecting the O2 sensor will raise the signal voltage above .2 volt. If the ECM and wiring are OK, the ECM should recognize the higher voltage, .35 to .55 and flash open loop when the engine is started.
3. Open loop indicates the ECM and wiring are OK. The Code 44 or lean exhaust is most likely caused by one of the items listed.