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· The Nuclear Option
5,996 Posts
So if u look at my last post about my po171 code problem u will understand this post.. so today I took out the Bosch o2 sensor I put in last month with original Gm acdelos. Now my fuel trim numbers were high especially my long tirm fuel trim. Now I went and looked a my MAF sensor reading and it was reading .20 to .30 lb/gram. (Whatever the name is) when it should be between 1.00 To 2.00… so I noticed it was low. Now I just replaced that sensor last month as well. It’s brand new.. but it’s a duralast brand… could the sensor gone bad? When it was brand new it would read 1.00 to 2.00 now could it have gone bad bc of the bad turbo that was just taken off and replaced? And also here’s the best part that gets crazy. WHEN I UNPLUG MY MAF SENSOR. My fuel trim numbers start to drop and go to the numbers that it’s supposed to be!!! That’s crazy. Also my fan will kick on and stay on for a bit but ends up turning off.. but my fuel trim numbers start to read what they should be. I then plug it back in and tho my fuel trim number continue to read good and stay good as I drive. Also the po171 code doesn’t kick on… but the MAF sensor numbers continue to read low numbers at idle. Also once I turn off the car and turn it back on. My fuel trim numbers go back to high numbers( basically running lean and going to get the po171 code again until I unplug the MAF SENSOR again… what is going on? Is it a bad MAFsensor bc it’s duralast? Or is the power train controls module faulty??? Ideas???
What's going on when you unplug the MAF sensor the ECM reverts to using speed density to select the fueling and commands open loop which ignores the oxygen sensors for the remainder of the cycle.

I only use GM sensors, most aftermarket sensors have a horrible reliability track record based on my experiences.

With every plugged in, What are the LTFT'S in gear at operating temperature at idle and what are they under boost?
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