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Richard, ASE Certified Technician
Category: Car
Satisfied Customers: 15511
Experience:  12 years Ford Lincoln/Mercury Jaguar dealership as a technician and shop foreman reparing all makes
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1999 Mercury Cougar: the Check Engine light..too lean..oxygen sensors

Resolved Question:

I have a 1999 Mercury Cougar and the Check Engine light is on frequently. The code indicates it is running too lean. We''ve replaced both oxygen sensors, nothing changed. Recently the check Battery light was on, replaced the alternator. Now all my indicator lights are flickering at all times, and never fully illuminating. Is it another electrical problem? What are my options?
Submitted: 9 years ago.
Category: Car
Expert:  Richard replied 9 years ago.

Hello and welcome to

The dtcs P0171 and P0174 bank 1 and 2 lean mean you most likely have a vacuum leak. The most common cause of the leak is from the intake gaskets. You can try spraying some carb cleaner around the intake to try to pinpoint the leak. If you have no leaks then you may have a faulty MAF sensor. As far as the lights blinking there is actually a service bulletin to Reroute the battery sense line from the engine compartment power distribution box to the B+ terminal on the alternator. I can send you the info in the bulletin if you would like.

Hopefully this answers your question and you accept. Positive feedback is appreciated and please let me know if I can assist you with anything else.

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