I have an 07 250 with 72k miles and I am constantly getting P0430. I cleared the code twice to see if it was just a small issue like bad gas, but it just came back at 256 miles after driving for the third time. I've looked online to see what it could be and the issues range from a o2 sensor to an engine misfire, so I'm not sure how to diagnose this issue. I want to start first to see if it's a sensor, I'm not sure which sensor it would be. Also is there a way to tell by the readings like voltage on a scan tool to see if the sensor is bad?

 

A very common cause of this code on our cars is an exhaust leak, usually under the Y pipe heat shield. This is especially likely if your car came from a state that uses snow melting chemicals on their roads. It's the first thing that I'd check for a P0420 and/or P0430.

 

Alright. I just went to a muffler shop and they confirmed that it was the passenger side cat that went bad. But I was searching online and I found that theres a federal warranty for catalytic converters that is 8 years or 80,000 miles. Would I be covered under that warranty since I'm under 80,000 miles?

 

Only if you're under the 8 years, and by 8 years, it means the date the vehicle entered service.

For sure, no leak at the y-pipe and the cat is actually bad?

 

I would question the accuracy of their diagnosis, especially since a P0430 indicates a problem with the reading on bank 2, which is the driver side, not the passenger side.

 

I have been getting a p0420 for months now, and occasionally trigger a p0430. I have headers though, with a stock mid pipe. I have downstream O2 extensions, and on my OBDLink app it looks like both of my upstream and downstream sensors are working well. Does anyone know the voltage that the upstream and downstream sensors are supposed to fluctuate between?

 

@MDHLexus here you go

 

+1

I had it due to a leak. Rusty pipe

 

My mistake it was driver side which is bank 2. And I went to 3 different sources and they all confirmed it was driver side catalyst. Not under the federal warranty because my car is over 8 years old so I have pay out of pocket. Just seems unusual for a catalytic converter to go that early with 73k miles on it, let alone on a Lexus/Toyota. Honesty my ideal option would be to just delete the cats and use o2 simulators, but metro Atlanta counties are emission regulated counties so I can't do that.

 

So here is a graph of my A/F and HO2 sensors. The graph on the top is downstream, and the graph on bottom is upstream. I have a pending p0420 and p0430, and have been intermittently misfiring for quite awhile (which I thought was carbon build up. Anyone have any clue why my sensors are all over the place?


IMPORTANT: I have headers, and the downstream sensors are in O2 Sensor Extensions (90 degree)

 

Check engine light came on p0037 changed the sensor, everything was fine for 2 or 3 days then the engine light came back on p0430 the day after that my car wouldn't start. Took it to advanced to get the battery tested they said it just needed charged but was still good. They did a quick charge car started and ran fine the check engine light was even off. Now 5 days later it's being hesitant when starting it and the check engine light came back on, anybody have any ideas? Thank you

 

If it's being hesitant to start. I'm sure your battery is not good, or your alternator is not charging the battery.

 

P0240 code

This was the fault causing my IS to throw a P0240 this is the right exhaust pipe sitting in the drivers seat facing forward. this triggered the EML/CEL to come on and the VSC. Leakis under the heat shield and in close proximity to the downstream oxygen sensor which see's the exhaust have higher than normal oxygen content and assumes the catalyst is not working effectively P0240 below threshold etc, I sealed it with a exhaust sealer and put a temporary piece of metal over the split it has fixed my problem and the light has stayed out now for a couple of months since the temp repair.

It may not be your issue but it's worth looking the exhaust did not display any signs of leaking or excessive noise .

 

mvrod, you are correct that the exhaust leak caused your P0420 code, but your explanation regarding higher than normal oxygen content is wrong . The reason you get a P420 (or P0430) in the presence of a leak is that the loss of hot exhaust gasses delays the light-off of the catalyst. The OBD2 test for catalyst efficiency runs just as the engine hits operating temperature after a cold start, and with the exhaust leak the catalyst hasn't gotten hot enough to start working yet.

As for the more recent issue faced by Sbier, I agree with MikeFig82 that the no-start/hesitant-start problem sounds like a battery or alternator issue.

 

I am getting p0430 code on 06 is250, catalyst system efficiency below threshold (bank 2), however, I am not sure which side cat is clogged, do you know which side is bank 2 and if is towards the front or back?