[shelby1]

The other day on the way to work my o2 light came on, concerned me at first but the truck continued to run fine but it used well over a 1/4 tank of gas for a 50 mile trip so I assume it has gone in to closed loop operation (limp home mode )so how do you check the o2 sensor and what are the spec's for it.
91 standard pickup 2.3 with Calif carb
Thanks for any help on this
Kenny

 

[CatFuzz]

There is tons of info about it on this sight. Instead of explaining it again, try using the search feature. :wink:

 

[BigSwede]

I doubt you are in open loop (closed loop is normal operation after warmup), that light is just an odometer based maintenance reminder at 90K miles or some multiple thereof, time to replace the O2 sensor. Once you get it replaced there is a switch on the back of the speedo to reset it.