engine ligh on steady

well sounds like a bad catalytic convertor and its not doing its job

The catalist sensor could be bad. They are called the downstrean O2 sensors. The catalist convertor may be bad, the best way to diag this is have a Ford dealer go through the step by step tests.

usally means the cats are bad and need to be replaced.but take it to someone u trust whose a mechanic and have them test it fully to make sure there arent any other things wrong also