I have an 01 Monte Carlo SS with the 3800 series, My check engine light came on for P0141 so I have just replaced both upstream and down stream 02 sensors with OEM AC Delco sensors. I cleared the codes and drove 150miles and the code keeps coming back. I checked all the wiring it seems to be fine. I also noticed when the car warms up it seems like it shifts hard but if I clear the ready monitors with my scanner the hard shifting goes away for a little bit then comes back along with the P0141 code. Please help!!! Thank You

 

Assuming fuse is good too?

 

I suspect a clogged catalytic converter.
How many miles on the car?
Is converter original?

 

Yes I checked the fuse that is good, I was suspecting a clogged cat too, it has 115000miles not sure if its an original cat but i assume it is. Would a clogged cat cause those systems? Also i pruchased the monte at 92,000 from a kid who said it sat for a couple months I have fixed a bunch a stuff on this car. The pipe had hole in it and i noticed the resonator was missing and it was just a straight pipe in place so i had the stock resonator put back on.

 

These symptons were present before i put on a new resonator and new upstream and downstream sensors. The check engine light is still on and it still shifts wierd sometimes but im pretty sure its not the transmission.

 

If the cat has a u-bend in it where the #2 O2 sensor is, it's probably original. Hard to get OEM replacements except from the dealer. Yes, it will cause these symptoms. Does the car have a California emission system or no. Should be a sticker on the top, driver side of the radiator. if there's no sticker saying so, then it's not CA.

 

Yes the converter does have a u bend where the 02 sensor is and its a new york car.

 

Uhgg!

NY may have the same emission requirements as CA and the cat is double the price due to higher platinum content. If found that out the hard way and there's only a few to choose from, I think Magnaflow is the only one legal to ship to CA or NY.

 

Just want to clarify. The cat is just a hunch. In reality, you should get a p0420 code (catalyst inefficient) for a clogged cat. I would start by checking the integrity of the #2 O2 sensor wiring harness and connector.

Here's how: