cel came on today key trick tells me p0138 1/2 o2s shorted to voltage.I know from searching there are a few sensors but so i dont waste time and money on wrong one which does this mean it is.Truck still runs no different just the cel is on.

 

If you have a federal emission truck (as opposed to california emissions...) that would be the post-cat O2 sensor. Follow the wires, they probably got burnt on the exhaust somewhere.

 

thankyou hey you for the quick response. There'e a lot of very knowledgable people on this forum.I did take a look under the truck and i dont see any damage to the wiring running to the sensors.I found one past the cat and one just in front. Is there a way to check or even to clean the sensor

 

I have never had any success cleaning a sensor....... might check and see if the connectors are in good shape...... (I know, they are in a fun place to get to....) If the connectors look good, and the wiring is all good, replace the sensor.

 

If, after replacing the sensor and clearing the codes, the code comes back, replace the sensor and clear the codes again. If it comes back a third time, you've probably got a catalytic converter on its way out.

 

bank 1 sensor 2 is the rear sensor.

shortage to voltage means there is 12volt on the signal wire.
either the wires to the sensor are pinched, mashed, shorted... or the sensor is bad.

the rear sensor doesn't do much except monitor the cat. if your mpg is good (as good as it gets) and running condition is good, and you don't have emissions testing, you could ignore it.

if you do replace it, unplug the old one and check the shape of the plug. there are 2 - square vs round. for some unexplained reason, the application guides are sometimes wrong.

 

Thanks guys I will check the connectors maybe a little die electric grease in them and if no luck i will change out the rear one. thanks again and will let know how things go.

 

Believe it or not the cel went out by it self 5-6 days after original post. I'll keep an eye out see if it comes on again