zajacjoe

O2 Sensors
I have received a P0430 Bank 2 Catalyst Below Efficiency.

I've used the DashCommand app on my phone and a bluetooth OBDII tool to record the voltages on the O2 sensors before and after the cat on both sides of the exhaust.

In the plot it looks like the Bank2 Sensor 2 (downstream) sensor is faulty due to 0 volts output at times.

Should I replace it or is something else going on?

Thanks!

VVTiBob

zajacjoe

No the car was just started when I ran the test. I'll repeat with it warmed up.

I don't believe there are any leaks.

Thanks...

Also I'm reading that the downstream O2 sensors are a real pain since the connector requires dismantling of the console.
Is that the case for the downstream passenger O2 sensor?

See this thread.

https://www.clublexus.com/forums/sc4...placement.html

Harold57

Can't you just splice the new one in instead of following it all the way back to inside of the console?

VVTiBob

zajacjoe

Here are the Bosch O2 Sensors. 15733 is the universal upstream, 15740 is the universal downstream

DundukovEM

It's not the O2 sensor.
As you can see on the graph - it's working fine.
It's your catalytic converters died. No efficiency.

Bgw70

DshngDaryl

You can try to replace your sensor, but most likely it is the cat and you will have to replace it. It's not that bad though. You can buy them on ebay for about $120.

I think that, because there is a different code for a bad O2 sensor and I have swapped plenty of rear o2 sensors, hoping that would solve the problem. It always came back to the cat. (I have done it 3 times)

I have a direct fit, bolt in aftermarket cat I bought, but didn't use (it turns out it was a gasket leak)

If you PM me, I will give you the details

DundukovEM

Don't have me wrong, but cat from eBay for $120 will last only year or two.
Just enough to pass the emission. That's what they made for and it's very cheap inside.
You know how expensive those rare earth metals what used in the catalytic process.
The OEM cat 18450-50350 cost ~ $1000 / each !!!

We have 3 cat conv: two on the sides of the engine block, and one down bellow pipe.
You'll never need to replace one down bellow (No. 3). Only on the engine block (No.1 and 2)

zajacjoe

Here is a set of plots for both cats done while hot. I'm getting a code on the passenger side but the drivers side does not look much better.

So looks like I need to replace both converters?

DundukovEM

Believe me, the driver side cat will throw the code right after you fix the passenger one

DshngDaryl

I know. Pretty amazing. And you need two of them. And what happens if you spend all that money only to find it you don't need them because it was the o2 sensor?

DundukovEM

Well, purely for calming the soul, start the process from replacing both O2 sensors Bank 2. Just to not feel sorry about cat price.
And then you will be 100% sure that you need them

FlopTop04

I had the same issue six years ago. It was a P0420 Bank 1 Catalyst Below Efficiency. The mileage was 94,000 miles. Tried both o2 sensors first but it was the catalytic converter. As mentioned, buy a decent quality converter. Mine was almost $400 but it is still going strong 31,000 miles and 6 years later. I only replaced the one that was bad and left the passenger side alone. BTW, Lexus recommends you replace the rear converter if either of the front ones goes bad. Think the quote I got from Lexus was right around $4,000 for the driver front and center converters, including labor and small parts ( gaskets and nuts ).