DarkRider

I have a 97 Z and the SES light has been on for a while
It is throwing code 0420 Catalyst System Efficiency Below Threshold (Bank 1)

Could that be the O2's, if so can they be cleaned or do I have to get new ones
Also Bank1, what does this mean

Also I have to buy a new battery today, what is the best kind to get that has a reasonable price tag

thanks Josh

lillbush5555

well you CANT clean 02's I tried you will need to replace them. as far as 97 thats OBDII (duh) as far as bank 1 (someone correct me if I am wrong) But I believe that is drivers side but it doesnt really matter because you cant just replace 1 02. you will need to replace 2 at a time 1 on each side I know it suxs but you HAVE to do it that way.

Now battery I went to autozone and got the mid grade for $50 and some odd dollars and it has like either a 2 or 3 year warrenty had it for 2.5 years and NO problems. cheap and good. I hope this helps you out

Matt

DarkRider

I can't remeber but does OBD II have an O2 before and after each of the cats, totalling four O2's in all

lillbush5555

yes...2 on the headers (well near) and 2 after the cats. as far as that code I dont know you need to determine if it is before or after the cat. it sounds like it MIGHT be after but I am not 100% sure if it is then you will need 2 square type plug 02's if not they are a rectangle.

Matt

DarkRider

Thanks for your help Matt

Injuneer

The low cat efficiency code is generated by the PCM based on the signal coming from the AFTER-cat sensor on the drivers side (Bank 1). Could be a faulty cat, could be a faulty sensor, could be bad wiring. Switch the two after-cat sensors side-to-side. If the problem follows the sensor to Bank 2 (passenger side) its a faulty sensor. If the problem stay on the drivers side, its a faulty cat or a wiring problem.

DarkRider

thanks, I will do that before I try anything, are the O2's hard to bust loose, my car has 115K mi.
Josh

DarkRider

I reversed the O2's and cleaned them up and no SES light so far and it is not pulling a code. I appreciate all the help.
thanks, Josh

DarkRider

The SES light came on again today and it is throwing the same code 0420 Bank 1. It could still possibly be the 02 sensor before the cat right? Shoud I try to reverse those? With 115K mi it could as well be the cat?
To test the wires for the 02, just use an ohm meter, can anyone tell me what it shoud read?

thanks alot

fastbird96

The P0420 code is AFTER-cat sensor, not before. Since you've already switched sensors and it didn't help, then either your cat is clogged or there is a problem in the wiring.

BirchMan98z

had the same code on my 95 when my cat went bad, I lost probably 3/4 of the power, replaced the cat and the 02 sensors and everything was back to normal.