P0401 Mercury -

Question

Why does an "!" come on in 02 Sable?

Answer 1

P0401 Exhaust gas reciruclation fow insufficient deteced

If your scan tool read "!" then this mean its absolute there are soft code condition and there are hard code condition soft code are pending codes are not fully matured, Hard code code right away, "!" is a hard code, the ECM will set if P0401 is ran and tested