Q: Check Engine light, code P0404.

Having the engine code is a great first step to getting your Pontiac Montana running up to speed again. This engine code is reading EGR, which stands for Exhaust Gas Recirculation. The EGR’s job is to redirect a measured portion the exhaust gases back into the engine. Once back inside of the engine, the now inactive exhaust gas displaces portions of both the oxygen and the fuel located in the cylinders. This will lower cylinder temperatures, which in turn lowers NOx (oxides of nitrogen) emissions. The computer in your Pontiac carefully meters the amount of exhaust gases that are recirculated. This keeps the vehicle’s pollutant emissions lower while additionally not changing the engine’s peak performance. When the amount of exhaust gas entering the cylinder gets too high the engine will not idle, causing it to stall. This is the reading of the check engine light you are experiencing.

The EGR repairs can be as simple as removing the EGR valve, thoroughly cleaning out the EGR port and reinstalling the EGR valve to correct the code issue. However, because this repair is connected to emission issues, it is best to have this issue inspected by a certified mechanic so all safety precautions can be met.