Cool 2004 Mercury Mountaineer Check Engine Light 2023. My local dealer has told me the pcm needs to be replaced and wants to charge me over $2100 to replace it. This can be done by unhooking both cables from the battery terminals (negative cable first) and waiting 30 seconds before reconnecting them.
However, it is the right place to start. Web 1 answer 2004 mercury mountaineer check engine code p0128 check engine light came on and had it tested and came up with code p0128. Web while driving, the computer of your mountaineer (ecu o pcm) monitors air/fuel supply and exhaust gases in order to verify that the engine is working properly.
