dtc for inefficient cat.

[frankenfinger]

Recently replaced after cat o2 censors on 1996 gmc sierra 5.3 ltr now getting dtc for catalist inefficiency bank 2. nothing wrong with cat. any ideas as im begining to guess and that just sucks. also recently installed magnaflow muffler. could it be a poss vac leak? i have been looking for leaks but nothing major found yet.any input from someone whos already been thru this will help.

[txab]

How do you know your cat is working as it should?

[frankenfinger]

im test. this would reveal if the cat was actually allowing unburned gasses to pass. at least thats what i think

[Duelin]

im test. this would reveal if the cat was actually allowing unburned gasses to pass. at least thats what i think

I assume by im test you are referring to I/M Monitor Readiness. And it says Catalyst Complete. If that is what you are referring to that is not a test of the cat. It is just telling you the system is ready to check the cat.

 

If that is not what you are referring to then just disregard.

[frankenfinger]

i was refering to state emissions test the one ness to renew tags. so any ideas now. i cleared all dtc and it only took about 20min of driving till the same code came back. is it poss i need to change the o2 sensors before cat?

[txab]

Well the ECM compares the information between the 2 sensors

[frankenfinger]

I understand that. my ? is why am i getting the code? poss the cat is bad I guess... could it have somthing to do with the muffler i just installed?