"Lack of HO2S-21 Switch, Sensor Indicates Lean"


i know i should be changing my O2 sensors soon, ( just turned 96K last week...) but this thing popped up yesterday, no drop in MPG, no power loss.......just lighted up after leaving work yesterday.........i did a road trip up to LA this past weekend, car ran perfect.......

i cleared the code yesterday, and disconnected the battery for a bit, went to work, and on the way home its came on again.......so........anybody get this code?


is it just my O2 sensors on their way out......?.....




:confused:

I have seen this code come up due to loose gas caps.

It means that the front sensor on bank 2 (drivers side) is not switching. Could be a vacuum leak just on that side, or the O2 sensor is bad. It is showing lean all the time.

it was the..........FUEL FILTER :D

gas cap was fine, no vac leaks.....

changed my filter (it was time already), and code hasnt come back, ill do some more driving tomorrow to make sure.

thanks for the help guys, weird little code this one is......

I had that about 3-4 months ago @ around 118,000 miles and replaced the forward O2 sensors, never came back. The sensors get 'lazy' and do not switch fast enough for the ECU, sets a code. Mine ran fine when it happened and I see no real difference since I changed out either, 'cept no CEL.