P0420 code?

[Go4broke]

OK I have my ses light come on and it reads P0420 in bank 1. So I replaced the bank 1 O2 senser(drive side header)but after a few hundred miles my SES light came on again same code same bank. why does just one bank get set off and not the other 2? should just buy 1 O2 sim for that bank or do I have to buy all 3? you guys that have had this code come up what bank did your code show up on?

[Bird_Of_Prey]

I'm currently getting the same code... I'm not sure where from yet. Do you have an exhaust manifold leak? I'm really starting to lean toward having a bad cat.

[RamAir95TA]

Check and make sure the oxygen sensor wiring isn't burning on your headers. The sensor can be good, but if the wiring is cooked, you'll throw that code.

[Takumi Fujiwara]

Another thing that is related to burning is just heat itself- heating up a wire makes it MUCH MUCH more resistant, and the idea of the wires is usually just a resistance based response, it would make sense that u heated it up and threw a code. so check for burning or see if u can cover up the wires and sensro

[Go4broke]

I checked the new O2 senser today the wire is fine and I made sure that the senser way on there tight.how do you check for manifold leaks? I drove 565 miles on the new senser before it cam back on.

[Ttop34]

Hey, I get that code, probably because of my lack of a cat though. You might try either an o2 sim or just putting a inline resistor in one of the signal lines of the o2 sensor. With no cat and a 1k-Ohm 1/4 watt resistor I would get a low voltage or no activity code. With a 100-Ohm resistor I get the 420 code. Next I'm trying a Linear-Taper Potentiometer where I can adjust the resistance from 5K to 0-Ohm, haven't messed with it yet though.

[navigatorbob]

I got that code on my 4.3L pickup about six months ago. I replaced the 02 sensor with no luck. After chasing down the problem with a multimeter, it turned out to be the EGR valve.

[hawgs]

ive got that code as well... i got it after i put my catco on about 1000 miles ago. i replaced the O2 sensor with a brand new one at the time, so i know thats not bad. i have an O2 sim i need to put in, and in theory that should work...

did you recently put your catco in? its probably the O2 after the cat that is causing that code, even though it says bank one.

[ March 31, 2003: Message edited by: hawgs ]</p>

[Go4broke]

I had my cat in for a few months and had my headers on for about 2 before the light came on.