Code 44 - Lean Exhaust Indication
The ECM supplies a voltage of about .45 volt between circuit Nos. 412 and 413 (terminals D7 and D6). The oxygen sensor varies the voltage from one volt (rich exhaust) to .10 volt (lean exhaust). The sensor acts like an open sensor circuit and produces no voltage when exhaust temperature is below 600°F (316°C). An open sensor circuit or cold sensor causes open loop operation. Code 44 is set when oxygen sensor signal at ECM is below .2 volts for one minute or more or if time since engine start is one minute or longer.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- Grounding diagnostic test terminal with engine running activates the "Field Service Mode" and allows the ECM to confirm either open or closed loop operation.
- A light out or "open loop" indicates presence of fault. Disconnecting O2 sensor will raise signal voltage above .2 volt. If the ECM and wiring are okay, ECM should recognize the higher voltage (.35 to .55 volt) and flash "open loop" when engine is started.
- Code 44 may be set by any of the following conditions: circuit No. 413 open (circuit No. 412 voltage will be over one volt), low fuel pressure, fuel contamination, EGR stuck closed or faulty MAP sensor. If these items are okay, the instructions at top of chart set a Code 44, and the "SERVICE ENGINE SOON" light is OFF more than it's ON or it's flashing "open loop", the oxygen sensor is faulty.