Northstar Engines and System Technical Discussion Discussion, SES Light - codes P0171 & P0174 - 2004 Seville in Cadillac Engine Discussion; Have a 2004 Seville with the SES light on referred to codes mass air flow sensor lean bank 1 and ...
Yes. The MAF was not your problem in the first place. P 0171 / P 0174 refer to fuel trim system, lean mixture, Bank 1 & 2. Usually caused by severe vacuum leak, in your case by a crack in the bottom of the bellows on the "plenum", that rubber/metal connector between the throttlebody and intake manifold.
The fuel rail and intake manifold must be removed and a new plenum assembly installed. Many pictures, parts, and diagrams of all this in my albums; click my username, open the profile - left column, 2 albums, 6 pages of your car and parts.
This thread belongs in either Seville or Northstar Performance: It has nothing to do with electrical systems. Better response in Engines: Northstar Performance. Off we go. (Yes, there are other threads in Electrical that don't belong there - we'll get to them)
Thanks Submariner409, had my friend do the work, didnt even have to remove fuel rails, found the plenum boot large split, wasted $$$$$$$$$$$ on 2 Mas air flow sensors and a egr valve, car runs great, so far ""NO"" SES LIGHT.
So I checked out all my vacuums hoses and there was a small crack off the intake piping that goes to the PCV. I put some electrical tape as a temp fix until i can buy new tubing, cleared the CEL codes and 320 miles driving and it still has not thrown the code. I really did not want to replace the plenum Behring the throttle body. Hope this was the issue.
So now 15 min later the CEL is back on. The search continues for the leak.