Code 44, Heated O2 Sens CKT, Lean Exhaust Indicated (VIN 8): Notes

ECM supplies approximately .45 volt between ECM terminals D6 and D7. If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. Heater circuit of heated Oxygen (O2) sensor is turned on when engine is running. Heated O2 sensor produces a varying voltage to ECM as engine reaches normal operating temperature. Voltage varies between .1 (lean) and 1.0 (rich) volt depending on conditions of exhaust gases in exhaust manifold.

Heated O2 sensor will not produce voltage until sensor reaches 600°F (316°C). When sensor is less than specified, open loop condition exists.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Code 44 will set when O2 sensor signal voltage is fixed at greater than .28 volt (280 mV) and with the following conditions:
- Throttle Position (TP) sensor is greater than 3 percent.
- No Code 21 or Code 33.
- System is operating in closed loop.
- Engine coolant temperature is greater than 155°F (69.5°C).
- Short term fuel trim is not at 128.
- Vehicle Speed Sensor (VSS) is greater than 3 MPH.