here is the problem my check engine light turned on.turns out i supposedly had a bad o2 sensor so i lifted the truck and i checked it it was fine so i checked the wiring to make sure it was connected.. now there is the wire that goes to the computer and another wire that goes down the frame towards the back of the truck(they are both connected to the o2 sensor ) im not sure if it is supposed to be a ground wire or if its supposed to be connected to anything . can any one help?

if you really dont know what im talking about i can try to get a picture and show you in a way

 

How did you check the O2 sensor?? Visually? You have 4 O2 sensors so what was the specific code you were getting.

 

i didnt know i had four im guessing that is where the other wires go too right cause i think that is what the other wires were for......can i get like a visual on where they are PLEASE i need to figure this one out or i cant pass my smog....oh and the code is p0104

i didnt see the other oxygen sensors so i need help

it was bank bb1 sensor 2 can any onw tell me where this is at please dont know the location

sorry the code is p0140

 

Take a look at the illustration in THIS POST. The difference between the 98+ and the 96-97 is the presence of a fourth O2 sensor. The 96-97 trucks have the two upstream (B1S1 & B2S1) as well as the same post-cat sensor (B1S3), but they also have pre-cat, emissions monitoring sensor only (B1S2) which is located behind the "y" in the y-pipe before the catalytic converter. In the 98+ trucks, the PCM was reprogrammed to use the output from the upstream fuel management sensors in conjunction with the post-cat sensor to determine the efficiency of the catalytic converter.

Was the pre-cat sensor the one you replaced? Before replacing any one of the emissions monitoring sensors, I would recommend swapping them. So take the post-cat sensor and the pre-cat sensor and swap them. If the code follows the sensor (moves from B1S2 to B1S3), then the sensor is at fault. If it does not, then it is likely a wiring or PCM problem.

 

so then i should change the sensors and the code should follow the bad one

 

If you swap the sensors from one position to the other and the sensor itself is bad, the code should follow the sensor.

For example...

Since you are getting P0140, this indicates that there is a problem with the B1S2 sensor readings. If you take the sensor out and install it behind the catalytic converter, taking the one you remove from behind the catalytic converter and installing it in front of the converter, and the code stays P0140 after the PCM has been reset, then the issue is not with the sensor since the code did not change to indicate the B1S3 sensor.