bcheney

2008 Cayenne base 3.6 check engine light on with these error codes read from Bosch. What can I check DIY? Vehicle runs good but cold start idlel is a bit shaky.

wkearney99

STFW seems to indicate a fuel pressure sensor as the culprit for P12A2 codes.

nodoors

P0431 and P0421 are exactly as they sound. Your secondary O2 sensors are picking up that your catalytic convertors are no longer operating at the designed efficiency level. How many miles are on your car? You can also see this if you are running crappy gas or the car is running too rich at times.

P2187 - I am not familiar with the v6, so you may want to check Touareg or Q7 boards to get to the bottom of that one.

bwross09955

I had these codes pop up on my v6 last year along with the unstable idle. The issue turned out to be bad pvc system. The pvc system is built into the valve cover and only comes as one piece. This my be an area to check.

bcheney

118K on the ODO

Tblue24me

Hello OP,
I got these same codes and didnt address them for awhile. I dont see any long term affect by not addressing them but Im glad I finally did. 955 Cayenne v6 with about 95k for mileage. I changed the evap valve but I dont believe I had to. The issue was clearly and definitely cracked plastic vacuum lines. I also changed the diaphram in the AOS. Best to remove it carefully by un doing the bolt beneath it and then each plastic vacuum line that goes into/from it. Then from underneath the AOS, use a small flat head screw driver and CAREFULLY pry the outer ring from each tab so the top just pops off. Clean it out replace diaphram from vanos-bmw.com...search there for the diaphram only and save a ton of cash...takes some shipping time but worth it.

Next vacuum lines...as you face the engine compartment, most (I think all) are on the left side of the engine. You can tell whats a vacuum line simply because the lines are a grey plastic. It fairly typical that the plastic, due to heat/cool cycle of the engine, that they become brittle and crack.....at joints...You will see that the cracks form where the plastic line fits onto a fitting or connector. You wont be able to simply cut the end off the plastic line and slip the new edge onto the fitting. I went with rubber reinforced hose (I think 3/8" and hose clamps tightened just to keep the hose on) since it was the same diameter hole as the plastic lines. Check them all...2 critical areas are (1) as a vacuum line goes through the firewall just behind the window washer fluid and the 2 very small lines underneath and in the area of the AOS (Thats why I say remove it carefully-ask me why...) Anyhow that should help you out. You can also order the plastic vacuum lines from the dealer but I understand they are expensive and you will have the same problem again whenever. Be thorough and it really only should take an hour...not difficult but be thorough.