Check Eng light on with Code P0172

Question

Need to smog Check eng light. What is the best order for replacement?

Have all ready replaced O2 sensor and Mass Air Flow sensor.

Answer 1

P0172 System too rich Bank 1

First of all, on a VW a faulty MAF sensor or dirty MAF can not cause a P0172. what can cause a P0172 are mainly mechanical condition such as low compression. a timing belt causing the valve timing to be off. These would be the most noticeable. with the engine performance. or plugged airfilter. , Fuel injector can cause a P0172 because you only have a P0172 and no misfire code. you can rule out the fuel injector, There a fuel pressure regulator ,  If its vacuum portion rupture it can seep raw fuel into the intake and would set a P0172, you can pull the fuel pressure regulator vacuum hose port out if fuel seeps out replace the fuel pressure regulator. The unfortunate part of your repair is the 02 sensor, VW at one time had to Recall the 02 sensor and reprogram  the ECM, these where the common cause for a P0172, For a fuel adaptation VW is required still to check the emission and the function of the 02 sensor front and rear and if there is a central 02 sensor , without charge. because of the age they may not honor it, but you can contact VW dealer  for the ECM update and 02 sensor replacement.