96 1.3 LSi with a P0420 Code

Hello, I have a 96 Geo Metro 1.3 LSi 2 dr with an auto trans. I purchased it a while back for my teen son. I knew it had a cracked exhaust manifold when I bought it. The thing is that when I bought it I drove it for a while with the cracked exhaust manifold. I never got a check engine light. Now, after replacing the manifold with a new one, I am getting a very persistent check engine light with a P0420 code. I know the code is for catalyst inefficiency bank 1. I am wondering if anyone with a similar car has had this code and what you did to fix it. I am leaning toward a new cat but I wanted others opinions first. Thanks in advance for any info you can provide.

While not the same engine, my '96 1.0 3-cyl had/has a P0420 code being thrown. The PO high-centered it in a snow-bank and wrecked the exhaust system. He did replace the exhaust from the CAT back before he sold it to me (not the CAT though).

I was getting the P0420 about every dozen or so times I drove the car, which I would clear with my OBD-II code reader. The only time it appeared to be resolved (for several months) was after I replaced the spark plugs. Then it came back.

I suspect a small exhaust leak before the last (2nd) Oxygen sensor in the system or that the 2nd sensor is bad.

There are a few things to consider here, before replacing the CAT:

http://www.obd-codes.com/trouble_codes/generic/p0420-catalyst-efficiency-below-threshold-bank-1.php

-Mike

Hello, I fixed it with the help of Mike Van, so I thought I would put this one to bed. I replaced the cat with a Catco 4096 direct fit replacement Catalytic Converter and a universal replacement rear O2 sensor. The cat came from exhaustwarehouse.com for $112, and the O2 sensor came from oxygensensor.com for $50. The check engine light did not come back on, and it passed emissions in Washington State. I replaced the spark plugs, timing belt, tensoiner and the water pump at the same time. I'm convinced the cat or the O2 was bad. I don't know which one was the culprit and I don't care. I saved enough money by buying online and doing the work myself to make replacing both items worthwhile. I thought I would let you all know how I fixed this in case someone else with the same car runs into the same problem. Good luck.