What would cause a check engine light to come on on a 1997 mercury grand marquie with 175000 miles try to get emissions test done on vehicle but wont pass while check engine light is on 46 ltr engine?

Answer 1

There are any number of reasons why a "Check Engine" light is lit. You need to find out what sensor, or sensors, are sending this an error code. You can do this yourself if you have a OBD II reader. This instrument plugs into a receptacle located beneath the steering wheel. It will give you the code. These readers can be purchased at an auto parts store. They come with instructions and will tell you what sensor the code refers to. Then you can effect the repair. These readers allow you to erase the trouble code and turn off the "Check Engine" light as well. All 1996 and later autos made for sale in the USA have this OBD II receptacle in the same location. Very good advise, but the DLC connectors are not in the same location. Yours will be below steering wheel to the right next to center console.