well here it goes.
i just last week bought my first dodge ram. its a 2000 with a 5.9, club cab, lift, love it but having some trouble with a 02 sensor code.
bought from old owner knowing it had a few bugs but managed to fix all but a couple. the previous owner took it to dealer and they told him it was the precat sensor and replaced it, but still comes up as a problem. the truck will at times run perfect but at other times it idles like crap. i only have the problem when idleing, on the road runs great.
any advice would greatly be appreciated.
im a newbie to this forum and ill get some pics up of it as soon as the weather clears up to get some good ones
thanks, sweeper

 

Do you have a check engine light?

 

yes, well it comes on and goes off. i think the code that comes up is po138 02 heater circut, but dealer says circut is ok its the sensor. sensor is new from the dealer

 

The sensor is bad or the CAT is not working properly due to the blown plenum you have.

 

blown plenum?

 

well have another question. is the 02 sensor in question the one before the cat or after cat?

 

google says P0138 is post cat.
O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

if you have a 4 02 california emissions, then its drivers side, post cat.
if you have a 2 02 federal emissions, then is passenger side, post cat.

inspect your truck and see what you've got.
check for obvious wiring problems, damage, missing or gutted catalytic convertors, missing or damaged o2 sensors.

http://www.obd-codes.com/p0138

 

thanks for the info. looked under the truck, it has only 1 cat and 2 02 sensors. talked to previous owner last night said the pre cat sensor was put on from dealer and the post cat sensor was put on by a independant repair shop. no telling where they got the post cat sensor. should i think about replacing it with one from the dealer?

thanks sweeper

 

^edit, oops i meant 1 cat and two 02 sensor federal emission.

is that your only code ?
does it poor when cold or when warmed up ?
do you know if the cat is intact, or gutted, or original?


if moneys not an issue i'd replace post cat. check wiring/plugs first.

 

And do a search here on Plenum.