So lately my Lexus GS300 was throwing the P0420 code and seldom the P0430 code a long with it. It would have a lag in acceleration like if i was waiting for a turbo to spool up. I checked as best as I could for exhaust leaks and such but nothing seemed to be leaking. I though it was the sensors that needed replacing but the CEL would be intermittent. So at my last oil change I decided to check for intake leaks which I did not come up with anything but a massively dirty air filter that I changed out immediately as well as took the whole airbox and cleaned that as well. While I was in there I remembered reading about the possibility that the MAF sensor could be dirty so I cleaned it with the Cleaner spray everyone uses. Put everything back together and bam no codes for the first tank of gas and smooth power. Now I get the P0171 Code thrown.

My question is: What is could be causing this?

I was thinking about replacing the bank 1 sensor 1 O2 sensor. According to http://www.obd-codes.com/p0171

 

I searched the 2GS forum for "P0171" and came up with 58 threads that discuss it. Below are a few but if you search for "P0171" you will find a lot more information on it.

P0171 finally fixed?!?!

P0171 - Lexus dealer unable to diagnose

Low idle on my 2001 gs300

 

Thanks Debonair, I did search and read prior to posting the question. I thought that in my case it was slightly odd to go from one code to another. But rereading the "P0171 finally fixed?!?!" thread made me look a bit harder for cracks in the hoses. Turns out there was a crack just out of sight. Its the PCV hose on the passenger side(?).
Using this photo as a reference it was the blue circle: https://www.clublexus.com/forums/gs-...-question.html

Which correct me if I am wrong is the "Breather Hose"?

http://www.ebay.com/itm/W0133-1739073-OES-Genuine-Breather-Hose-/231559516846?hash=item35ea05d2ae&vxp=mtr
http://www.partsgeek.com/gbproducts/...rZEaAuPZ8P8HAQ

Now a follow up question: Is there an after market option for this hose or a cheaper option than the links I have found? Could I just get a vacuum hose? I don't really have a caliper to get the inner and outer diameter sizes for the hose.

 

did you check lexus of south Atlanta or ebay for an OEM replacement?

 

Glad to hear you found it. Any hose will work as long as it fits without leaking. You can take the broken hose to an autoparts store and match it up to their bulk hose. Buy the right size in the length you need and you are back in business. Since the universal hose is not rigid and molded to a specific shape make sure it does not contact any moving parts under the hood. I also recommend you pass on the colorful fast-&-furious style silicone hoses too.