2004 Chrysler Pacifica check engine light came on. Ran codes. Replaced erg valve and oxygen sensor. Can't clear codes and nothing new comes up

Sounds like you need a new ERG valve and/or ERG sensor.
It supplys oxygen to balance the amount of the gasoline and oxygen your engine recieves if the balance is off it can make a car do what yours is doing
.If you can drive your car over to a auto parts store in your area and they should have a code reader to test your car for free.

If the light comes on at times there will be a code stored. Go get codes read before you spend money on other repairs. I dont know how the engine got gunked up with 50k miles on it and with todays cleaners in oils and fuels so im going to call BS on what the dealer told you. How does he know?, did he pull valve cover, intake,or use a scope to look into the engine?

It is hard to say exactly what to do with your problem because the information you posted is inaccurate and incomplete. There is no code "1059" for a 2004 Chrysler Sebring. The only code I could come up with that is even close is code P0159, which is a "slow response" code for a downstream oxygen sensor. If this is NOT the code you are reading, then you should re-post it with the correct code designation EXACTLY like the code reader gives it to you. It would be very helpful to mention also which engine your Sebring is equipped with.

If this IS the code you have, the sensor will most likely have to be replaced. It should be noted, however, that the system needs to be checked for contamination like silicone sealants being used on the exhaust flanges or burning antifreeze or engine oil. If there is a source of contamination and it does not get repaired, it will only cause a new sensor to also fail.

To answer your question about what it does:
The downstream O2 sensors monitor the post-catalyst oxygen in the exhaust system to allow the engine computer to determine if the catalytic converters are in good condition and working properly.

This may not be a solution, but I would contact Chrysler customer service/owner relations number in your manual, and explain that it has been an ongoing problem since .... and has never been cured and that you feel it should still be covered under warranty. They might even contact dealer and give them some advice where to look for problem, as well as continue warranty coverage for said problem, or refer you to another dealer.

you most likely have a p0404 dtc for egr valve if you go to autozone they will scan it for free if this is the case then replace the egr valve what happens is it sticks open causing an internal vacuum leak stalling out the engine.

HI, the PO420 is an oxygen sensor code.

that would be your HO2 sensor. It's located in the left hand exhaust manifold closer to the top of the engine. It usually takes a special socket to remove one. If you have any doubt, take it to a shop and have them replace it for you. This sensor effects fuel and driveability, don't go to long without fixing it as it may cause damage to your catalytic convertors.

2 possible problem come to mind:

• Bad ignition switch; faulty switch will occasionally make contact but not every time
• Bad starter; less likely but possible; a bad starter will function when it's cold but when it heats up, takes much more power to make it work

I hope this helps with your problem and wish you the best of luck. Take care!
Greg

If the light isn't flashing, it is safe to drive. If it is flashing, then catalytic converter damage can result. Have a parts store check the codes for you and come back and post the code.