Interesting CEL with an easy fix
 

A couple of weeks ago I stalled my '05 987 BS and upon restart got a CEL. Got it to a shop to have them check the codes and found mis-fires on cylinders 4-5-6 plus both banks of O2 sensors out.

The misfire codes were easily cleared out and did not come back. However, the O2 codes (P0031, P0051, P0036, P0056) came back right away. The shop couldn't get to the car right away so I drove home and did some more research.

I went and reviewed the fuse box and noticed there was a circuit dedicated to the 02 sensors (D-6) so went to check the fuse box in the car. There was no fuse in D6! I also noticed that D-4 (DME) had a 25A instead of required 7.5A. I moved the 25A from D4 to D6 and put the proper 7.5A fuse in D4. Lo and behold, the CEL goes away.

I drove the car 500 miles and no CEL returned. I am calling this one fixed.

I don't understand why the code wouldn't have been present all along when the fuse wasn't present and only exhibited after the stall. Also noting that you live in CA, I would have thought without the O2 sensors powered the car would never have passed smog.

Who sold you the car and when? How and why did the fuses get fooled with?

Good questions - my guess is that the fuses were present the last time the car passed smog as it is current.

I just bought the car a month ago from a dealer. There have been some interesting items such as this that didn't come up on the PPI. Other examples include missing lock nuts from the wheels and a missing Bose subwoofer unit. I have replaced both.