DTC 44

Code 44 Wiring Diagram:

Code 44 - Oxygen (O2) Sensor Circuit (Lean Exhaust Indicated):

CIRCUIT DESCRIPTION:
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 volt.) The Oxygen (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.

TEST DESCRIPTION
Number below refers to circled number on the diagnostic chart.
1. Code 44 is set when:
- Oxygen (02) sensor signal voltage on CKT D7 is less than .2 volt for 50 seconds
- System is operating in "Closed Loop"

DIAGNOSTIC AIDS:
Using the "Scan," observe the block learn values at different rpm and air flow conditions to determine when the Code 44 may have been set. If the conditions for Code 44 exist, the block learn values will be around 150.
- Oxygen (O2) Sensor Wire
Sensor pigtail may be mis-positioned and contacting the exhaust manifold.
- Check for intermittent ground in wire between connector and sensor.
- MAP Sensor
A (MAP) sensor output that causes the ECM to sense a higher than normal vacuum will cause the system to go lean. Disconnect the MAP sensor and if the lean condition is gone, replace the sensor.
- Lean Injector(s).
- Fuel Contamination
Water, even in small amounts, near the in-tank fuel pump inlet can be delivered to the injectors. The water causes a lean exhaust and can set a Code 44.
- Fuel Pressure
System will be lean if pressure is too low. It may be necessary to monitor fuel pressure while driving the car at various road speeds and/or loads to confirm "Fuel System Diagnosis" CHART A-7.
- Exhaust Leaks
If there is an exhaust leak, the engine can pull outside air into the exhaust and past the sensor. Vacuum or crankcase leaks can cause a lean condition.
If the above are OK, it is a faulty Oxygen (O2) sensor.