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My 2006 is250 RWD has code P0420 that appears. I've checked for exhaust leaks and no exhaust leaks. My upstream air fuel ratio sensors have been changed about a year ago and now this error. My car has over 180k miles on it. There is no noticeable drop in performance or anything and I don't seem to have any signs of misfires etc.
i have access to techstream and wondering what kind of tests can be done to test if the cat is gone? Where exactly is the cat? Is it located under the vehicle and is removing it all done from under the car?
The other thing I could think of is could it be the O2 sensors after the cat? These are still the originals. Is there a voltage check I can do for that?
There are 4 cats in the system, 2 in the midpipes aren't monitored. The primary cats are integrated into the exhaust manifolds, with the efficiency O2 sensors responsible for your code just downstream of them in the midpipes. My troubleshooting would first focus on those two sensors (they're shrouded from the outside elements, I cut my shrouds off after breaking my O2 socket and just used a, IIRC, 7/8" open end), and you have to pull the carpet up near the inboard footwells to disconnect their harnesses. The plugs pull out through the tunnel. It's a pain. If those sensors are known good, then I would replace the cats...and since I was already going through all that trouble, I'd go with some aftermarket headers, sensor extenders, ect. but you're not me. The OEM manifolds with integrated cat can be had used for relatively decent (for a cat) prices, but I'd sell the car before I paid dealership pricing for anything, especially a catalytic converter..
There are several apps that allow you to monitor O2 data live. I am not sure if Techstream does or not. Likely does. If not buy an Elm OBDII Bluetooth or wifi adapter and download Torque Pro. Total cost $25 and you have tools to monitor engine health. The downstream sensors behave very different on and off the throttle so you'll need to do a little reading.
While waiting for OBD tool run a couple tanks of seafoam or techron fuel cleaner through it and open it up a bit on a long hill. This could clean the sensor and clear the error.
Does the error Catalyst System Efficiency Below Threshold Bank 1 have any effect on car other than throwing the error and emissions?
It definitely disables stability and traction control. Not certain, but maybe cruise control too. Of course if you live in a place that does emissions inspections, you won't pass.
As 2013FSport suggested, you can look at live data from the O2 sensors. The front sensor should swing between rich and lean as the ECU trims the fuel injection. The rear sensor should see very little of that activity once the catalytic converter gets hot enough to start working. Most frequent cause of P0420/P0430 on our cars is an exhaust leak that slows catalyst light-off until after the efficiency diagnostic runs, but you said you already checked that.
Most frequent cause of P0420/P0430 on our cars is an exhaust leak that slows catalyst light-off until after the efficiency diagnostic runs, but you said you already checked that.
I checked it as much as I could visually. Should I take it to an exhaust shop to properly check it? Is there a specific place to look and how can check for sure?
I checked it as much as I could visually. Should I take it to an exhaust shop to properly check it? Is there a specific place to look and how can check for sure?
Most common place for leak is at the Y-pipe, often under the heat shield. You may be able to hear it with the engine running. A good exhaust shop should have a machine that can check it by pressurizing with smoke.
Most common place for leak is at the Y-pipe, often under the heat shield. You may be able to hear it with the engine running. A good exhaust shop should have a machine that can check it by pressurizing with smoke.
Just found an illustration of the exhaust system online. Is the red highlighted area the main bank 1 and bank 2 cats? and the blue section being the mid section pipe? and the brown lines on the blue section being where the HO2 sensors go? I'm not to familiar with the exhaust system sorry Where exactly in the illustration is the Y section under the heat shield i should specifically be looking ?
Not the best picture. The pipes that join the rear two cats with the resonator have a Y-joint (visible). That Y-joint is covered by a heat shield (not visible). I've had the same thing as you since I got the car, waiting for a few parts to arrive (new exhaust gaskets, two subframe bushing stoppers that didn't arrive with the first shipment.. go figure) and then I'll be looking at this as well. I deff. have a leak in the exhaust somewhere, and that's the only place I haven't really checked
Also, p0420/0430 just light up the CEL, nothing else is affected. Keep a scanner with you and check periodically, the biggest danger is that you won't notice something else if it pops up.
The Y-pipe is basically the blue section in your diagram. This thread, where the poster paid $14 to do a cheap and sloppy repair, may be useful to see a typical place that the corrosion occurs: https://www.clublexus.com/forums/is-...cel-p0430.html
So I had the exhaust inspected at an exhaust shop. I mentioned to them that I get the cat efficiency below threshold error and it sometimes goes away by itself and stays off for weeks and then comes back. They couldn't find any exhaust leaks. They said only the heatshield around the cat is corroded and for age and mileage that's normal. They said the Lambda Sensors look new, these are the air fuel ratio sensors which I replaced not so long ago. The only sensor that's still old is the heated oxygen sensors post cat ones. They suggested that it could be the cats itself starting to break up inside and suggested replacing the cats. Considering the amount of work and cost involved is there any risk/danger in running with failed or failing cats? Could I put spacers on the post cat heated O2 sensors?
So I had the exhaust inspected at an exhaust shop. I mentioned to them that I get the cat efficiency below threshold error and it sometimes goes away by itself and stays off for weeks and then comes back. They couldn't find any exhaust leaks. They said only the heatshield around the cat is corroded and for age and mileage that's normal. They said the Lambda Sensors look new, these are the air fuel ratio sensors which I replaced not so long ago. The only sensor that's still old is the heated oxygen sensors post cat ones. They suggested that it could be the cats itself starting to break up inside and suggested replacing the cats. Considering the amount of work and cost involved is there any danger in running with failed or failing cats? Could I put spacers on the post cat heated O2 sensors?
I just changed both 02 rear sensors this past 4th of July. I kept getting the P0420 on bank 1. First it was intermittent then more consistently after resetting the code. I new it wasn't the cat convetter as the car still ran great prior to the P0420 being triggered. Swapped both rears, and no cel since then.
I just changed both 02 rear sensors this past 4th of July. I kept getting the P0420 on bank 1. First it was intermittent then more consistently after resetting the code. I new it wasn't the cat convetter as the car still ran great prior to the P0420 being triggered. Swapped both rears, and no cel since then.
Rear O2 sensors as in the ones after the cat with the wires going inside the cabin floor under the carpet? Which sensors did you replace it with? I was looking at denso universal fit one which require the connector from the old sensor to be cut out and crimped. Would it just be cheaper and easier to put spacers on the sensors?
Rear O2 sensors as in the ones after the cat with the wires going inside the cabin floor under the carpet? Which sensors did you replace it with? I was looking at denso universal fit one which require the connector from the old sensor to be cut out and crimped. Would it just be cheaper and easier to put spacers on the sensors?
Yes post cat "rear". I went with DENSO bought off rockauto.com. When searching they will say downstream.
06-07-19 | 06:18 PM
Testing catalytic converter
Where exactly in the illustration is the Y section under the heat shield i should specifically be looking ?
