: Whats the deal with my o2 sensors

06-25-10, 08:29 AM
ok, in the shop i have a 02 dts i just put a motor in. car has 3 o2 sensors right, the rear 2 are the only ones that are throwing codes. i replaced the rear two with new delco sensors, and still the same codes. the first one is p0155, then p0141. i am positive all the grounds are hooked up, checked for vacuum leaks, the only thing i am not sure about is it has a emmision pump or smog pump what ever you call that, any way it all hooks to the exhaust. could that be my some of my problem. every thing else works great any help would be great

06-25-10, 01:08 PM
Those are "heated" O2 sensors and the code is for the "Heater Performance". Sounds like the sensor is working, but the heating element (to bring it up to operating temperature faster) is not.

06-25-10, 03:47 PM
That may be due to either a twisted O2 sensor pigtail, a broken ground, or the ground connection itself. Other posts on this a while back.

06-25-10, 04:54 PM
i replaced all o2 sensors with new delco, pig tails are good a the same with the connections, i will recheck all my grounds. can any one tell me the ground that runs the o2 sensors or any other areas to check.

06-25-10, 07:24 PM
I have been through every thing twice or more, still cant figure it out. i have done lots of caddy swaps mainly 94-99 this is the first 2002 i have ever swaped and this one is a little different than what i am use to. i live in kansas right know it is 90 degrees out side, first start up every thing was working great no codes, car ran all day before the codes came up, the first code was p0155 so i cleared it hoping it was nothing. jumped back on it the next day no problems ran great, then code came back. the owner supplied new delco o2s plugged them in didnt fix it, so i went through and double checked every thing grounds vacume leaks every thing looked great. does any one know about that emission pump or what ever that is that hooks to each manifold could that be my problem. or the car looks to have had some exhaust work done maybe bad cat. i am trying to explore all options. any one have experience with these style northstars or be able to maybe show me a tread that might help.

06-26-10, 01:12 PM
Briefly, I think the purpose of the air pump(s) is to force air into the exhaust stream for about 30 seconds after cold or warm startup (but not if the engine is at operating temp and was just turned off briefly). The combination of the additional air with an enriched fuel mixture causes the catalytic converter (and O2 sensors?) to heat up and begin operating more quickly, thereby reducing emmisions.