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Ford Taurus failed smog test due to MIL/Check engine light on because of fault code P0141 & P0140.

Hi.. My Ford Taurus has failed the MIL/Check engine light due to warning lamp failure. Fault code P0141 & P0140. What causes this to fail. Also what causes my car to fail the emissions test.
Answer:

Trouble code p0140 indicates a problem with the oxygen sensor circuit pertaining to the second oxygen sensor located on Bank 1 (this is the side of the engine where cylinder number one is on). Trouble code P0141 indicates a problem with the heater circuit of the same oxygen sensor. The oxygen sensor is the main component responsible for letting the your car's emissions computer know how much fuel is in the exhaust system at any given moment. The Oxygen Sensor sends an electrical signal to the ECU, letting the computer determine exactly how much fuel it should continue to deliver to the combustion chambers. If for any reason the 02 sensor (oxygen sensor) does not send accurate information to the computer or it is "lazy" in sending the correct signals, the fuel delivery program can be altered. The computer may then present either too much or not enough fuel to the combustion chambers and therefore cause an emission failure. These trouble codes are pretty straight forward and should not be hard to diagnose. It sounds like a simply disconnected oxygen sensor harness, or in the worst case scenario, a melted and defective oxygen sensor connector/harness. A smog check repair station should not have a hard time identifying this failure. As far as what causes your car to fail the smog check... that's simple. Your car is hooked up to the smog machine during the smog inspection and the trouble codes in your car's computer are relayed to the smog machine. Soon as the smog machine notices a trouble code it automatically fails your car. posted by SmogTips Support

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