Question

I changed my fuel filter on a 2004 Mercury Mountaineer and now I get engine code P0191. Could it be a bad filter?

Answer 1

It's possible but unlikely. You may have turned the ignition switch with low pressure.

Any other symptoms? If no other symptoms are present, you should try erasing the code first.

P0191 MERCURY Code - Fuel Rail Pressure Sensor Circuit Range/Performance
Read more: https://www.autocodes.com/p0191_mercury.html