DTC 44

DIAGNOSTIC CHART





WIRING DIAGRAM

INSPECTION PROCEDURE

Circuit Description:
The Engine Control Module (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 025 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(s) below refers to circled number(s) on the diagnostic chart.
1. DTC 44 is set when the 02S signal voltage on CKT D7.
- Remains below .2 volt for 50 seconds.
- And the system is operating in "Closed Loop".

Diagnostic Aids:
Using the "Scan Tool", observe the block learn values at different rpm and air flow conditions to determine when the DTC 44 may have been set. If the conditions for DTC 44 exists, the block learn values will be around 150.
- 02S Wire. Sensor pigtail may be mis-positioned and contacting the exhaust manifold.
- Check for intermittent ground in wire between connector and sensor.
- Manifold Absolute Pressure (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 oxygen sensor signal and can set a DTC 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. See "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 O2S.