P0420... Catalytic convertor...

[mvbighead]

Just got error P0420 on my 05 Equinox.

As I'm new to a lot of things in the garage, I've been doing some research to determine if it is, in fact, the cat. General googling suggests that it's possibly the O2 sensors, but most likely the cat (most suggested it was 99% likely it was the cat).

All that said, provided above is a graph of the 02 sensor readings. Based on what I've read, the rear O2 sensor should read flat. It seems that it is bouncing with the front O2 sensor (as the engine goes back and forth between rich and lean). Since it isn't flat, I am assuming the code suggesting it is the cat is correct, and that I should proceed with replacing it?

What say you guys?

For what it's worth, I called a muffler shop I'm familiar with, and he seemed to think it was possible it was an O2 sensor, and might not be necessary to replace a "$700" cat. That conflicts with what I've read. Also, I've found a bolt on cat on Amazon for $280, (http://www.amazon.com/Magnaflow-2399...1&s=automotive). I don't have any welding tools, so this may be my best option if I end up going this route.

Just looking for feedback, and any additional advice to consider before purchasing this. I've cleared the code for now and am awaiting the tests to re-complete to see if the error comes back. I loaned the vehicle briefly to someone who jokingly referred to driving it hard, and I am just wondering if some rough driving caused the code to trigger. But, if a new cat is what it needs, a new cat is what she'll get.

 

[satyajitmenon]

How many miles on the Equinox?

My truck has 168k miles and it just started throwing a similar error (known issue with high mileage Titans). Am in the process of swapping out the stock nonsense with LT headers and custom-fab mid pipes instead of the expensive OEM crap.

 

[LTC8K6]

Cats have a pretty long warranty. 8/80 I think.

 

[thedarkwolf]

Have you cleared the code to see if it comes back yet? I've had the code show up twice in 5k miles and 8 months on my 200k mile vibe. I just cleared the codes and ignored it. Till it is showing up consistently it isn't a big deal. You can also just buy a generic universal cat and have a shop weld it in which won't cost much.

If you believe some dude on youtube you can also take your old cat off and soak it in bucket of water with laundry detergent in it and clean it out well enough to get rid of the code for awhile lol.

 

[phucheneh]

If you need to pass an OBD2 emissions test: The code is based upon the catalyst monitor running and failing. So complete all the monitors that you can while keeping the speed down, then get the car as hot as possible and haul ass down the interstate. If it passes, drive (slowly) to the emissions place....and plan on buying a new cat by next year.

 

[Black2na]

only way i would think if it was an o2 sensor if its also throwing an o2 code with the cat inefficiency code. had a similar issue with my 03 silverado when i had it after 4 o2 sensors being replaced i still had the cat codes. newer OBDII sysems are pretty on the ball. not to mention general interwebs census points at the CAT and try an stay away from crap aftermarket cats they tend to not work out so hot. seen alot of CEL problems from aftermarket cats. some cars just require OEM replacement.

 

[thedarkwolf]

You can always do the spark plug defouler trick to get the aftermarket cat to pass if it trips the light. If you have emissions checking and they look too closely they may not be too happy though.

That will also work now if the light keeps coming on if it just isn't as efficient as it should be anymore. If the cat is plugged though you wouldn't want to do that.

 

[SearchMaster]

I have had that on my last two (high mileage) cars (00 Maxima and 98 Accord) - replacing the upstream O2 sensor resolved it both times. Minimal cost and effort.

 

[mvbighead]

Equinox is at 118k. It did register as a bank 1 issue, I forgot to add that bit.

As for emissions tests, I don't have that problem. I just have the code. The only other thing I've noticed is that my last fill up was at 19mpg, and prior ones have been about 22. I do a lot of highway driving, so I generally stick towards the upper end of the range. Just not sure if the person I loaned it to (my dad) actually did run it rough and somehow cause this to pop up.

As for the part I linked, some are suggested that aftermarket cats can cause problems... I was under the impression that Magnaflow was a good aftermarket part. Is it not?

 

[mvbighead]

Oh, and I did clear the code. I am still awaiting the cat test to finish.