Debbey Mack

I need some help here. I have a 2001 Silverado 1500 4.8 and I have tried everything I can think of to get these codes cleared out they are the PO430 and PO430pd I have changed the plugs and the wired and reset everything and this all started after the gas pump needed was changed out. I am not the smartest girl but I do atleast know my way around the truck. but my daughter needs to be going back to school and I know this code does have an effect on gas efficency and every penny counts. I don't know exactly which O2 it could be to check or what so any help would be greatly appreciated. Frankly this is burning us girls out for the last week trying to figre it out. There is no shops where we live here either and the ones nearest just want a fortune to rework the whole exhaust and everything is what they say and I know enough to know that is BS.

kevinkpk

Have you replaced right hand side pre-cat O2 sensor?

MrMarty51

After doing a search I found this web site.Be sure You test the o2 sensors on both sides of the convertor,if either one of the sensors,upstream or down stream of the convertor is going bad then it will seem that the convertor is not functiong up to par.
Remember that any thing related to the emission system is usually under an extended warranty and if Your pickup is not expired on that program then the faulty components will be replaced free of charge.
if You can not get it into a warranty facility for one reason or another then I would thoroughly read through this webpage and perform all of the tests suggested,in order as listed.
A simple volt/ohmeter will be a great tool if Your scan tool can not show You the outputs of the o2 sensors.
I did read where the engine code described wo`nt cause any efficiency problems except for at startup when the engine is cold.
I hope this helps.
EXPLAINING TROUBLE CODES PO420 - PO421- PO430 - PO431

Debbey Mack

No, I hadn't replaced anything in the O2 sensors. I know that it has 4 and not sure where to start and which one to start at also. And while me and the girls were out heading to the store after I made that post it started to act up really bad and start chugging and sputtering and flashing the check engine light so I whip into AutoZone and have them read the codes and it says that it is alsoontop of PO430 and PO430 p/d it also throughs out PO308 and that it now is misfiring on number 8 or there is a leak in the vaccuum. I couldn't see or find anything. so I bought new plugs and wires to get at the task right away. My daughter has to go back to school on sunday and this is the only decent reliable vehicle that i trust for her to be in going so far away from home in.

Debbey Mack

Thanks and I will start in on this as like I said she has to start back to school late Saturday the latest I can push it is early Sunday morning since she has to drive to Kentucky in it. Will start in the morning and Thanks again.

MrMarty51

It definetely does sound to Me like it is an oxygen sensor,or,possibly a couple of them.
Do You have a book ??? I have a Haynes manual for several of My GM vehicles and they tell how to test the sensors with a volt meter set on the Milli Volt scale.
If You do`nt have a book,let us know and I will respond with the detailed information on how to go about testing them.
Each sensor will need to be tested starting with a cold engine{open loop mode} reading 0.1 to 0.2 volts and the engine warm{approximately two minutes} should be 0.1 to 0.9 volts,if the oxygen sensor fails to reach the "closed loop mode" or there is a very long time before it does then the sensor needs to be replaced.
I do`nt have a very new book so I ca`nt tell You the color of the wires You need to backprobe but the older ones were the black wire - and the purple or pink wire +.
Just be sure that if You are working in a garage You have plenty of ventilation.
Also if Yoiu have to remove any sensors they will usually unscrew if the pipes or manifolds are warmed up.
There is a special made socket for removing the sensors with a cuttout for the wires,the socket is six sided to aid in the prevention of rounding off the corners of the sensor{s}.

MDTAHOE

You need to replace the bank 2 (passenger side )catalytic converter. The code it catalyst efficiency below threshold bank 2. It is telling you that the converter is not cleaning the exhaust properly. They o2 sensor are what is seeing the problem not causing it. The code is set when upstream (before the cat) and downstream (after the cat) o2 sensors voltage match each other. PO420 (bank 1) and PO430 (bank 2) and bad cats 99% of the time. Until the cat starts to melt down, break apart or get restricted the code will have no effect on performance or fuel economy. Plugs, wires, filters etc... will NOT cause this code. Very very very (did I say very) rarely does a bad O2 cause this code. If the O2 was bad you usually would have a code for o2 high voltage bank 2 sensor 2 or a code for the heater circuit on either upstream or downstream o2. Do yourself a favor and stop wasting money on parts and put a new OEM cat on

Debbey Mack

so are you saying that it needs to have the cat replaced on the passenger side only or both or what? I replaced the plugs and wires today and it needed it there was misfiring on the backside of a plug and it still ran rough and I replaced a vaccum line and it threw a new code of po308 and cleared the codes again and once again back to Po308 pd

Debbey Mack

po308 pd

MrMarty51

My book says the code PO308 is nimber eight cylinder misfire.
Be sure that the plug wires are all in the right order and that the wires are all seated corectly on the plugs/distributor cap.
No,I`m not saying that the cat. convertor is bad and needs replacing,is what I am saying is that if an oxygen sensor is bad and reading out of parameters with the other sensor,that may be ahead or behind the convertor is bad,that it will probably send a code that the convertor is1nt doing its job when in all actuality it could possibly be a bad oxygen sensor.
If You have a book it will give detailed instructions for testing the o2 sensors and save You from buying four sensors,replacing them and then being rid of the code,or,if the convertor is in fact bad then along with spending about fourty five bucks apiece for o2 sensors You then will also be having to replace the convertor.
by testing the sensors first and possibly finding a bad o2 sensor it could rule out that the convertor is working proper and it is a bad sensor that would be kicking out the signal to set the code.
I have found a couple of times where a code was set and then discovering that a sensor plug wasnt properly seated and latched in place.
IF the emissions warrany has not run out the vehicle could be under warranty and the GM dealer would be fixing any o2 sensor and or the convertor if it is bad.
My 93 GMC pickup has 246,000 miles and the convertor is still working as it should,although,I have had to replace the o2 sensor once so the convertors them selves gives very little trouble considering how many vehicles are still running with them.