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Good morning Scanner Danner Techs!
I have a 98 Ford Taurus SE Comfort 3.0L 24v DOHC (Build 11/97)
When the electric fan kicks in around 212°F, 02 voltage slowly drops to .000mv. When the electric fan turns OFF, 02 v slowly rises to normal. This engine has an EGR flow code and Lean code. The EGR passages are clogged and it has a bad intake leak, which only runs rough when cold. I'm guessing none of the later issue's have nothing to do with the 02 v dropping. Is it possible I have low charging system output? Battery is strong and the alternator is putting out 13.5v. The dash lights dim a little when there is any type of electrical load applied like fan, power locks...
Just to make sure I understand, the upstream O2 signals both go to zero (and stay at zero) with the cooling fans on? What are the fuel trims doing during the same event? Is the Loop status staying closed? Do the O2's do the same thing if you turn on the A/C and force the fans to run?
I've seen many vehicles that will momentarily drop the O2's to zero when large loads are applied. But they recover and go back to normal almost immediately. I believe it has less to do with the electrical load, and more to do with the idle speed compensation.
