Just looked up in Auto data, "CO levels are electronically controlled, No adjustment possible. If CO not as specified. Check for air leaks in intake and exhaust systems, Carry out component and electrical tests" As you have had a Diag done, would think components etc ok, Would also have thought, that if done at a garage, they would of checked emmisions as part of the checks, with air flow. If you checked for errors your self, recheck, Air flow intake, was probably a part sticking, Has your air intake filter been changed?? Might sound silly ? BUT I was nearly killed because the main dealer on my car did not change it, Put a screwdriver through it, but did not change it.
Sheepdog
March 2011
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.