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rpmdiag, Tech and Instructor
Category: Mercury
Satisfied Customers: 8065
Experience:  Since 1975
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I have a 2000 mercury grand marq that the check engine light

Customer Question

i have a 2000 mercury grand marq that the check engine light comes on after resetting the ecm. useing the live date mode on my scanner it shows that the o2 sensor on number two often starts at 0 then goes to as much as 800. does this mean the sensor is bad or is it the ecm. the other o2 sensor reading also move around a lot but don't start at 0
Submitted: 1 year ago.
Category: Mercury
Expert:  rpmdiag replied 1 year ago.

Hi, I’m Ron and I can help you.
I have been in this business since 1975 and also teach automotive repair. I am confident we can resolve your problem together. Please understand that I don't know your skill level. I can't see, smell, hear, or touch the vehicle either, so it may take a few replies to get to satisfactory results. Please be patient!
I also try to give all of the information you may need, expecting a “positive rating” in return. I will also continue assisting you after you have rated me, if necessary. If there is any reason I cannot get a positive rating, please let me know why “in advance”, so I can go another direction for you. I am sorry you’re having this problem; I’ll help you through it.

It's possible, but you first need to check for excessive lean or rich conditions, then check the computers ability to compensate for initiated commands from the tech such as inducing lean and rich conditions. If there are no responses then then the sensor is bad. Hope this helps.

Thanks, Ron