GMC Repair: oxygen sensors?, powertrain control module, vacuum leaks

Question
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Followup To
Question -
I have a 2002 chevy impala. The engine light came on and I took it to this place and they got a code of P0171. They said it was the front and rear oxygen sensors.($413.00 total) The next day the light came on again, now they said it was the wires to the sensor was low voltage and changed it. On the way home the light came on again.:( Now they said there are four wires and they will change them. Do they know what the hell they are doing and did I get ripped off? Thanx
Answer -
I don't know what they did or did not find so I cannot tell you if you were ripped off or not, but I hate to think you were.

This code is set when the vehicle see that it is running rich, you may want to check for a vacuum leak around the intake, or something loose on the air intake tube.

I may be able to help more, but I need to know if you have a 3.4l or a 3.8l engine.

I have a 3.4L, They have been checking for vacuum leaks but of coarse they could have missed something. They said this code is the toughest to diagnose.

Answer
It is a difficult to diagnose concern, and also if there was any physical damage to the wiring harness, they may have missed checking for blown fuses. I remembered having a couple of cars like that.

Also there could be shorts in the wiring harness where it routes around your A/C accumulator, that is a very common place for the harness to rub and it is near the Powertrain Control Module which is what reads the sensor data. This type of short is only found with a 3.4L that is why I asked.