silverbullet2007

OK guys I have 3 codes. #1 is PO171, #2 is PO174 and #3 is PO621. I checked for vacuum leaks everywhere and found none. I found bosch and denso O2 sensors on Ebay and Amazon for as little as $25.00 each shipped. I have the tools for changing the sensors and I'm ready to order the parts and go to work but that still leaves PO621 Gen Lamp L control circuit. code. My local repair shop wants to change the 4 O@ sensors and go from there. What do you experts think? Vette runs great no change.

schpenxel

I don't buy O2 sensors going bad on both banks at the same time.

Stock tune or no?

If you want to replace them just buy some AC Delco ones off Amazon. That's what I'm using. I don't think they are the root of the problem though based on the limited info you've posted.

silverbullet2007

OK it is fixed. The problem was a split grommet going into the brake booster. I took the car to a great shop and the found it using a spray bottle of water. He sprayed around the engine until the RPM changed. All is good now.

BlindSpot

Good that you got it fixed!

It is so tempting to take the shotgun parts replacement route, but not good especially if you're paying a shop to do so. With codes, the answer is there with intelligent diagnostic techniques.