Code 44 - Lean Exhaust Indication
The ECM supplies a voltage of about .45 volt between circuits 412 and 413. The O2 sensor varies the voltage from 1 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 (310°C). An open sensor circuit or cold sensor causes open loop operation. Code 44 is set when O2 sensor signal at ECM is below .2 volts for 8 seconds or more or if time since engine start is 1 minute or longer.
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- 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, the 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 413 open (circuit 412 voltage will be over 1 volt), low fuel pressure, fuel contamination, EGR stuck open or malfunctioning MAP sensor. If these items are okay, and instructions at top of chart set Code 44, "CHECK ENGINE" light is "OFF" more than "ON" or flashing "open loop", oxygen sensor is faulty.
Field Service Mode:
- Engine Running, Diagnostic Terminal Grounded
- Open Loop - "Check Engine" Light Flashing At A Rate Of 2 Times Per Second
- Closed Loop - "Check Engine" Light Flashes At A Rate Of 1 Time Per Second