po420 code

**matt89** · 06-26-2007, 07:15 PM

will driving the car with this code on 4 1 week hurt anything? (cat low efficiency) Is there a code for a plugged cat? A cat that still flows but doesn't clean is okay, but a plugged one is a no no for limping along until gm gets the new one.

**Wesman** · 06-26-2007, 07:35 PM

The fact that the catalytic efficiency is "below threshhold" won't hurt the car or your engine at all. Its merely bad for emissions.

However, if the cat is plugged up, then that is definitely bad for your engine. There is no code for that, the O2 sensors merely detect whether the cat is cleaning the exhaust properly, not whether it is flowing well.

If you feel any decrease in power, the cats are probably getting plugged up. Good time to install some LT headers

**79Firebird_99TA** · 06-27-2007, 05:59 AM

Originally Posted by matt89

will driving the car with this code on 4 1 week hurt anything? (cat low efficiency) Is there a code for a plugged cat? A cat that still flows but doesn't clean is okay, but a plugged one is a no no for limping along until gm gets the new one.

Been there - done that.....with a `01 Maxima. You need a catalytic converter. You have an o2 sensor upstream and downstream to that CC. The downstream o2 is measures the efficiency of the CC.

**SeVeReDiStOrTiOn** · 07-19-2007, 04:14 PM

The light is annoying but the car will be ok...the cats will probably have to be replaced to pass emissions though. I had a p0420 and just tuned the code out...still passed hippie cali emissions.

Did you ever get that letter from GM? They extended the cat warranty to 100k if I remember right...

**79Firebird_99TA** · 07-29-2007, 05:09 PM

Originally Posted by SeVeReDiStOrTiOn

Did you ever get that letter from GM? They extended the cat warranty to 100k if I remember right...

No....I never did. The girl that had the car divorced me....LOL.
Now it's her problem.

**rel3rd** · 07-29-2007, 06:55 PM

Originally Posted by SeVeReDiStOrTiOn

The light is annoying but the car will be ok...the cats will probably have to be replaced to pass emissions though. I had a p0420 and just tuned the code out...still passed hippie cali emissions.

Did you ever get that letter from GM? They extended the cat warranty to 100k if I remember right...

FWIW,
My letter from GM says 130,000 miles...

**SeVeReDiStOrTiOn** · 07-30-2007, 07:22 AM

Originally Posted by rel3rd

FWIW,
My letter from GM says 130,000 miles...

Sweeeeet...even better

**7901 ws6** · 07-30-2007, 09:42 AM

Its a CAT. I had that code when My car was at 25K, the Repair under Warranty was replace the CAT.

**madmatt** · 07-30-2007, 03:23 PM

Yep, dealership replaced mine under warranty.

**ws6drew** · 07-31-2007, 11:10 AM

I've got the same error code and the same letter from GM (also meaning I sill have the Service Engine Soon light on). When they replace the cat's will I need to replace the sensors too? If so, how difficult is it to do that? Not a huge fan of giving the dealership a shitload of money for something I can do myself... just need a little guidance

**2001NBMZ28** · 07-31-2007, 11:29 AM

Know people who have had their cat replaced under the warranty - didn't have to spring for new sensors. 99% of the time P0420 or P0430 is the cat, and the sensor is doing what's it's supposed to - monitor the cat.