Mercury check engine codes

Overview

Mercury vehicles (discontinued after 2011) used Ford engines. Codes follow Ford patterns, including EGR feedback sensor faults on older engines.

Codes notably common on Mercury

• P0171 System Too Lean (Bank 1)
• P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient
• P0455 Evaporative Emission System Large Leak Detected

Mercury specific notes

• Mercury shares Ford engines. On older engines with a DPFE sensor, P0401 is frequently caused by the sensor or its hoses.

Owner's manuals

Official Mercury owner's manual / owner portal (manufacturer site; we do not host copies).

Recall lookup

Check open Mercury recalls with your VIN at the NHTSA recall lookup.

Sources

• https://knowhow.napaonline.com/dealing-with-ford-p0401-code-issues/
• https://www.nhtsa.gov/recalls

Sources checked October 2026. Bulletins apply only to the models and years they list.

All other codes

These work the same on Mercury as on any vehicle:

P0420 P0430 P0300 P0301 P0302 P0303 P0304 P0174 P0440 P0442 P0456 P0128 P0135 P0141 P0101 P0299 P2135