i've been looking online, and i just called napa, and everything is showing that i should have 3 O2 sensors in my truck. but, i had replaced the catalytic converter not too long ago, and i only saw two under there. i see one right in the cat where the two down pipes meet, and there is one between the cat and the muffler. i pulled codes on my truck, and it shows a few for the bank 1 sensor 1 spot. is there an O2 sensor that i am missing?? thanks

 

i have the same deal, only ones i know of are one b4 and one after cat, i think we are right 2

 

so would the one in the O2 sensor be "bank 1 sensor 1"?

 

possibly.

what are your symptoms, mine just went nuts flooded then ran like ****, turned out to be sensor 2, i think its the one in the catalytic converter for you.

 

my truck has been killing fuel since i changed the catalytic converter. i think one of the O2 sensors was damaged either from the clogged cat or maybe from the install. i'm getting like 5-6 mpg's. in park, at about 800-1000 rpms it puts out a little black smoke. it smells like fuel. i've checked the codes, a few of them were for the O2 sensors (3 for the bank 1 sensor 1 unit).

oddly enough, even with all these too-much-fuel syptoms, i still got a code for 'bank 1 too lean'

i erased all the codes, and i got 'bank 1 sensor 1 O2 sensor low volts' again, so it looks like that sensor is bad.

 

'bank 1 too lean' is a bad ingector i think
'bank 1 sensor 1 is the o2 before the cat (you do only have 2 o2's)
id change out both o2s at the same time and see if that fixes your problem if not then the next step would be to check your ingectors but they could be out because of the o2s

 

ya the low volts what screwed me over, get a new one if it throws that i would say, also replace the other one like ryan said, not a bad idea i didnt cause i didnt have the money all at once, maybe some other day , hopefully its not your injectors

 

They only have the 2 O2 sensors one before the cat and one after to check efficiency of the cat. The 02 sensor will also make your truck run lean. if it is not reading right it can send the engine into LIMP mode and run rich. If ur running lean check fuel pressure and fuel VOLUME, that one must be stressed the pump might be giving you pressure but not enough volume to the injectors.