Hi folks, I own a first generation prius that's been showing the P0420 code for quite awhile. I've been dealing with it, but it predictably failed inspection last month and now I have to get it fixed before the end of this month. A toyota dealership in Queens gave me an estimate of $1400 including parts and labor, but I'm hoping to do it for less than that. Does anyone know any shops near Brooklyn (even in NJ is fine) that have experience with Priuses and are willing to work with you. Ideally I'd like to try to replace my cc with one like these that claim to work in a first generation Prius. I've read some of the past threads about the P0420 code and know it could be the oxygen sensor, but I'm not handy enough to determine that myself, so I'd like to find a place that is honest and can check that out or alternately install a generic cc. There's a thousand shops I can take it to, but honestly I don't know one from another, so any help or guidance you can offer is very much appreciated.
The Gen 1 prius has an insanely stupid plate in the exhaust that is controlled by a vacuum diaphragm. This obviously gets rusted shut from salt and rust and heat. And then your car won't run. You could have a legit catalytic problem or O2 problem or likely the HCAC valve is stuck. Oxygen sensor general info | PriusChat I recommend you go to any auto parts place and borrow the OBD-II sensor and go to View Data and view the live data for the O2V11 and O2V12 the upstream should cycle between 0.1V and 0.9V. If it does not the wire is bad or the O2 sensor is bad. The downstream O2V12 should read under 0.5V when cold and 0.6 or 0.7 after the ICE runs for a few minutes. Make sure you put on the A/C and are in P with engine running for the OBD-II tests. You should be able to have a mechanic get under the car and work the valve plate in the exhaust, but they will need pictures as this is the only exhaust valve thing I know of and no one has ever seen it. The only "fix" aside from high temp grease on this valve is an entire new exhaust for well over $1500.
Good Prius friend, Hobbit, turned me on to this group. These folks have been pretty good about pointing to folks they've trained: Auto Careers Development Center - Hybrid and Electric Vehicle Repair Training You might give them a call and/or send an e-mail explaining what you are after. Bob Wilson
I still maintain that the HCAC failure mode is the bypass and protects the catalytic converter. If you have downstream reading problems it is either bad O2 sensor or you were running rich for a long time and damaged cat. I doubt anyone with a Gen 1 needs a new exhaust because of that stupid HCAC bypass for start up conditions. Check the downstream O2 reading. Then decide, and also I am willing to bet the better solution is to drop the exhaust and remove the spring on the HCAC valve and leave it in normal-every-other-car-on-the-road-including-Gen 2-mode. The reason you are getting a code is that most of the exhaust isn't going through the catalytic converter because age and road salt likely has frozen up a moving piece some insane japanese engineer kludged in there for US emissions.
Thanks for the responses, that's the first I've read about the valve plate possibly causing the problem. So if I'm understanding right it's possible to disable the valve, leaving it in the open position and then the code will disappear? For what it's worth, I have had problems with the car stalling out, or taking multiple attempts to start. Not very recently, but since the warning light ! has come on. That made me think there's a good chance I have an actual problem and not just a faulty O2 sensor. Good to have some new things to consider and bwilson I think I'll contact that group to see if they have any recommendations.
You could have a plugged cat or maybe a bad O2 downstream, or maybe the ICE is running rich from MAF, etc. and hence the stalling etc. Any auto parts store you can borrow the OBD-II and read the "View Data" and see the STFT LTFT, O2, MAF, CTS, etc. So go check the fuel trim it should be under 12% hopefully long term is 0%. Check the O2V12 and make sure after the car warms up it starts at like under 0.5V and when it is warm it goes above 0.6V. It helps to turn on the A/C or other ways to keep the ICE running. Also, is your oil level above top line, and pull off the airbox and look down in there with the key out and twist the throttle plate and see if it looks ok or is sticky.
