got the codes

**rajiv1998** · 01-16-2008, 10:47 AM

Hey guys, a while back i made a thread about my SES light comming on. Well today i called a friend to come over and we decided to check out what was wrong. We did the diagnostic test and 2 codes came up. P0430 "Catalyst efficiany below threshold bacnk 2." Now I know for a fact that the cat is fine becasue i had it checked out and every1 said it wasnt bad. I also replaced my 02 sensors about 2 months back, so i know for a fact its not that. I just dont know wut the fuck it is, and its driving me nuts to see that dam SES light on. The next code was P0300 "Random missfire." I dont know what this is either. Its seems to be running on all 8 cylinders and i double checked my plugs, wires and coilpacks. Everything is on nice and tight. From what i hear i am comming to the conclusion there MIGHT be an aftermarket cam in the car? Its choppy during startup and has a little bit of a rough idle, however this can be from the missfire. Any1 have any suggestions? The car runs strong with no hesitation when u step on the gass, and all the guages and fluids are fine, oil has been changed every 3k miles with moble 1, so im kinda lost.

**2001NBMZ28** · 01-16-2008, 11:00 AM

Visit gearchatter.com and look up the code descriptions/diagnostics for your year if you haven't done so already. P0430 is almost always the cat if the rear 02 and wiring is fine. You could also swap the rear 02's from bank to bank, clear all codes, and see if it throws P0420 for the drivers side.

**Y2KPewterSS** · 01-16-2008, 02:06 PM

Just because you bought an 02 sensor two months ago, doesn't mean it hasn't already taken a shit on you. I would not be surprised if your 02 is bad, especially if you bought a Bosch replacement 02.

**0rion** · 01-16-2008, 02:15 PM

switching it is the easiest way to tell if the sensor is bad, if the code follows it then that's your culprit but I would question why it's bad after only 2 months. Also, how do you check a cat out? Who told you it was fine? My money is on a bad cat.

**Marc 85Z28** · 01-17-2008, 11:50 AM

Originally Posted by rajiv1998

Now I know for a fact that the cat is fine becasue i had it checked out and every1 said it wasnt bad.

Who is "everyone" and how did they verify that the cat wasn't bad? It is very possible for a catalytic converter to fail due to inefficiency and not affect engine performance at all. A catalyst inefficiency code is caused from a failed converter 99.9% of the time. A failed rear O2 will NOT cause a catalyst DTC regardless of what anyone tells you. The P0300 DTC could be LOTS of things. Could even be your catalytic converter... What plugs do you have in the car?

**rajiv1998** · 01-21-2008, 05:51 AM

Well now the car is misfiring. It will jerk and shake when u try and get it moving from a dead stop. It will hesitate for a second the run fine. It runs great under WOT and doesnt do anything above 3k. I dont know wtf is wrong and im pulling my hair out trying to find out. Those are the only 2 codes that show up. The missfire thing is driving me crazy becasue the car just jerks and shakes. I checked my plugs and wires and they seem to be fine so idk wut it is. Any1 have any advice?? And the plugs i have are NGK TR555-IX with the MSD 8.5 super conductor race wires.