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Chris (aka- Moose)
Chris (aka- Moose), Mercury Technician
Category: Mercury
Satisfied Customers: 1913
Experience:  16 years experience with Mercury
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I have a 2000 mercury grand marquis that sets the check

Customer Question

i have a 2000 mercury grand marquis that sets the check engine light and codes out problems with the emission system. using my live data on my scanner the # ***** o2 sensor has erratic reads going down the road. it reads from ooo to 800 but does not ever stay
within a 100 differential . before replacing would like to know if it could the pcm or the o2 sensor
Submitted: 1 year ago.
Category: Mercury
Expert:  HDGENE replied 1 year ago.

Hello, depends on what code(s) are setting and if you are having an issue with the upstream precat convertor sensor or the catalytic monitor sensor they operate differently

Customer: replied 1 year ago.
the precat sensor is the one that is giving bad readings number 2 on code readerthe
Expert:  HDGENE replied 1 year ago.

Ok the drivers side(bank 2) upstream oxygen sensor is not reading properly. its setting a code so the check engine light is on. Whats the code P0174/lean. rich code? heater circuit. need some more information please.

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