DTC 44

Code 44 Diagnostic Chart:

Code 44 Circuit Diagram:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volt between Terminals "3" and "20" of the ECM (If measured with a 10 Meg ohm digital voltmeter, this may read as low as 0.32 volts.) The O2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down to about 0.10 volt, if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below approx. 360°C (600°F). An open sensor circuit, or cold sensor, causes "Open Loop" operation.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 44 is set, when the 02 Sensor signal voltage on CKT 412:

^ Remains below 0.3 volt for 2 minutes or more, And the system is operating in "CLOSED LOOP"
^ 02 sensor must reach a temperature of 360°C (600°F).
^ Throttle is off-idle. Inlet air temperature switch is "OFF."
^ Vehicle is at low altitude.

DIAGNOSTIC AIDS:

^ 02 Sensor Wire - Sensor pigtail may be mis-positioned and contacting the exhaust manifold. Check for ground in wire between connector and sensor.
^ Exhaust Leaks - If there is an exhaust leak, outside air can be pulled into the exhaust and past the sensor. Vacuum or crankcase leaks can cause a lean condition.
^ If M/C solenoid does not click with ignition "ON" and test terminal grounded and there is no Code 23, check for sticking solenoid.
^ Inlet air temperature switch may be open. Should be closed below 32°F.
^ If Code 44 is intermittent, Testing and Inspection