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**ssiebor14** · 10-27-2013

P0420 catalyst efficiency bank 1. What doesthis mean. Plus abs light came on out of no where there is a loud humming whenever I get up to 50 mph and whenever I brake there sounds like there's rubbing noises or like is rubbing the bumper but it's not. Help?

**Scottydoggs** · 10-27-2013

http://www.obd-codes.com/p0420 could be a bad cat, or o2 sensor. hows the car running? is it gut less or feel down on power?

the abs light is a bad hub, same for the hum sound. jack each wheel one by one up lugs tight, then push and then pull the top of the tire, if it moves you found your bad hub.

**ssiebor14** · 10-27-2013

I've dine the hub. None are bad. And it feels down on power I gutted the cat already so it might need the 02

**02NavyBlue** · 10-27-2013

Does the humming sound like this? Our impala makes this noise at any speed, changes pitch as the speed increases. I'm thinking wheel bearing, I'll check soon. It may take a while before the bearing wears out and gets some play.
http://www.youtube.com/watch?v=OZSfx0817Uo

**Scottydoggs** · 10-27-2013

what year and model car you have? the gutted cat could be the cause.

**ssiebor14** · 10-27-2013

The code threw before I gutted it and the hum sounds like a roar only at 50 to 60 then stops. But I have 98 gtp sc

**Scottydoggs** · 10-27-2013

the roar could also be a bad tire. try rotating the fronts to the back, maybe you can hear it move.

and the code, now you have no cat, so unless you get the rear o2 sensor tuned out, your gonna have that code forever, or put a cat back on.

**ssiebor14** · 10-28-2013

I'll just get the emulator for 45 on zzp. But I rotated the tires still coming from the frint

**ssiebor14** · 10-28-2013

I'll just get the emulator for 45 on zzp. But I rotated the tires still coming from the frint

**ssiebor14** · 10-28-2013

Also the wheels and the hub are fine.

**Scottydoggs** · 10-28-2013

take the plugs off all the hubs, clean and grease them, while your there, check the wires to each hub for damage.

if you cant find anything still get it scanned, your at the end of the free checks. the speed sensor can and do go bad in a good hub. most of the time the hub being bad throws the abs sensor off and trips the light.

**primem** · 10-28-2013

for the p0420...a cheap fix that may work is to install a spark plug anti-fowler in the 02 bung and then re-install the rear 02. it will shield the rear 02 from the exhaust stream enough to keep the front and rear cross counts from setting the dtc.

Best fix is new cats. if you go that way don't buy cheap cats. The basement line cats have low cerium content (the oxygen storing element in the cats) which will set the p0420 right from new.