sonus

I got my check engine code vagged, and it reads:

2 Faults Found:
17521 - Oxygen (Lambda) Sensor; B1 S1: Internal Resistance too High
P1113 - 35-10 - - - Intermittent
17544 - Fuel Trim: Bank 1 (Add): System too Lean
P1136 - 35-10 - - - Intermittent
Readiness: 0000 0000

After some looking at the archives I found that this most likely points to the pre-cat oxygen sensor. However (and at the risk of sounding like a complete noob) I swear I hear a hissing sound when the hood is up and the engine is idling that I'm pretty confident wasn't there before. I noticed that at least one person mentioed a similar set of codes and the possiblity of a vacuum leak. Could my issue be a vacuum leak or some other sort of leak instead? The car doesn't feel any different and still pulls strong. What's the best way to look for a leak?

Rocky-in-Connecticut

those are the most likely leaks, it is a good idea to replace those lines in any regard as they are bound to crack open at some point.

RoberTT-WWCD

You might also have a failing MAF.

How many miles on the car? I replaced both O2s around 90K. Both were toast.

OldSchool AG

"internal resistance too high" means it's done for.

the hissing noise is probably just normal injector cycyling. if you weren't listening for it before you probably wouldn't have noticed.

regardless, replace the O2 before doing anything else.

sonus

Thanks everyone! Now I a bit more educated and ready to tackle this check engine light.

sonus

Would I feel a boost leak in day to day driving? Car has 86k miles.

maaliish

O2 errors can be caused by leaks so I would check that first.