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pO420 and pO137?

01GrandPrixTURBOGT

01GrandPrixTURBOGT

New member
My engine light came on a few days ago so i took it to get scanned and i had to DTC po420 and po137. At first my car ran fine then i lost a lot of low end. When i clear the codes it runs fine. Each time i clear them the time it takes for them to come on again shortens. Ive read a lot of different thing son how to fix but cant find a definite answer.Thanks for help.
 


do you have any mods on the car or is your screen name wishful thinking? cause if your car is mod'd then might want to start looking at the work done.
 
No mods I thought about turboing but decided to top swap soon. PO420 says catalyst efficiency below threshold bank1 po137 Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
 


I'm reading the rear sensor is low voltage aka lean or incorrect and the code for catalyst efficiency. I would check/replace that rear sensor if it's installed, clear codes and see if the cat eff comes back.

It doesn't seem like it's clogged does it? Around 3000rpm gets boggy?
 
I wouldnt say its boggy just lost power mostly low end under 3k. When i clear the code i can spin my tires but when the codes on for a few days it will hardly chirp around a corner. So i wouldnt think the cat is clogged.
 
I'm kinda having the same problem but no codes........boggy and gutless in low rpm's. The idle is lopey too.......almost a rhythmic up & down....kinda surging. As I mentioned before, I had a cracked check valve on the air injection and it apparently allowed enough exhaust to escape to make it run well enough......not great or normal. The key indicator that pointed me to the converter being plugged was that the check valve got so hot that it not only cracked the housing, it totally melted the vacuum chamber and the aluminum plug area, spitting molten aluminum all over the firewall. Once I found and fixed the check valve it now runs as you mentioned....much worse...boggy and no power........but no codes. That points me in the direction of a plugged converter.

I just bought a Magnaflow direct fit and I'll be putting it in this week when it arrives.
 


Sure will :D.......should be here no later than Friday the 6th.
The ZZ Performance one was nice also, but since ZZP used the Magnaflow converter anyway, and the pipe design was similar on both pipes (straight, no J bend), I just opted for the Magnaflow cause (in total) it was almost $100 cheaper......and it's all stainless
I ended up getting the whole thing off EBay for $164 shipped to my door so I can't complain........
 
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