P0430 Highlander V6 (Oxygen Sensor)

[MaximaGuy]

Finally got the P0430 on Highlander (not surprised after 182K miles) and most probably its the O2s.
Baffled they lasted this long - but time to replace them.
I have a V6 and it is CA speced and unsure how many sensors are there on these vehicles.
Any ideas which ones to replace first to address this code and brands to buy them would also help (leaning towards getting it from dealership/NGKs).

 

[goodtimes]

The code doesn't mean it has to be the sensor is bad. Vacuum leaks after the MAF sensor wreak havoc on the signals and the sensors can appear faulty when they are not. On an 02 Camry I discovered both boots going to the throttle body and MAF sensor box had cracks on the bottoms of them. This allows air in after the MAF and codes for sensors are thrown. New boots and everything was perfect again. Sensors were fine, originals. Get the spec on the sensor and check them with a meter as a last resort. A code does not mean to automatically replace the item throwing the code.

 

[Trav]

I doubt its the O2, more likely the cat on a Toyota. A P0430 is the same as a P0420 just the other bank.

 

[MaximaGuy]

Originally Posted By: Trav
I doubt its the O2, more likely the cat on a Toyota.


Pre-cats and cats, they are designed for the life of the car. They cannot go they are dumb components.
The ones that go out are the sensors and off course vacuum leaks (which I shall go and check right now).

 

[Charlie2015]

Originally Posted By: Trav
I doubt its the O2, more likely the cat on a Toyota. A P0430 is the same as a P0420 just the other bank.


This is great advice - exactly what I would have suggested.

 

[clinebarger]

Originally Posted By: MaximaGuy
Originally Posted By: Trav
I doubt its the O2, more likely the cat on a Toyota.


Pre-cats and cats, they are designed for the life of the car. They cannot go they are dumb components.
The ones that go out are the sensors and off course vacuum leaks (which I shall go and check right now).


How did you come to this conclusion? You really don't believe a Catalytic Converter can degrade & lose it's efficiency??
P0420/P0430 codes by themselves usually mean you have a catalyst below the efficiency threshold.

Trav has been diagnosing vehicles for a LONG time.....No reason to dismiss his advice!!

 

[bullwinkle]

Originally Posted By: MaximaGuy
Originally Posted By: Trav
I doubt its the O2, more likely the cat on a Toyota.


Pre-cats and cats, they are designed for the life of the car. They cannot go they are dumb components.
The ones that go out are the sensors and off course vacuum leaks (which I shall go and check right now).
Obviously never had a Nissan Altima (or any other modern vehicle)-cats go bad all the time!

 

[14Accent]

Toyota's are much smarter than that...

It won't set a P0430 code for a failing O2, 99% of the time. It will set:

O2 heater circuit codes
O2 stuck rich/lean codes
O2 insufficient switching codes

Any cat efficiency code almost guarantees that the oxygen sensors ARE working. So, as long as your fuel trims are in spec (to rule out vacuum leaks and injector issues), it's almost guaranteed to be the cat.

 

[slacktide_bitog]

P0430 is a catalytic converter code, not an oxygen sensor.

However, you should replace all the o2 sensors when replacing the cat.

 

[MaximaGuy]

Ok. Would cleaning the upstream cats with seafoam removing an O2 sensor and spraying into the honeycomb cat.
Soak it overnight and then fire it up.

 

[14Accent]

You can't really "clean" cats. They work based on an inherent chemical reaction to exhaust gases. Once the reactant inside the cat is compromised, nothing will bring it back.

One and done.

If you're trying to skirt emissions testing, just install a spark plug non-fouler under the affected bank's downstream oxygen sensor and drive long enough to clear the monitors. Most stations will pass you with that method, however illegal. Y

 

[Wolf359]

Originally Posted By: MaximaGuy
Originally Posted By: Trav
I doubt its the O2, more likely the cat on a Toyota.


Pre-cats and cats, they are designed for the life of the car. They cannot go they are dumb components.
The ones that go out are the sensors and off course vacuum leaks (which I shall go and check right now).


Not to pile on, but yeah, cats go bad all the time. Usually either vacuum leaks or mixtures that are off can fry them. If everything is working normally, they should last the life of the car. But some don't. As others said, mostly like the cats are fried, but you might get lucky and find an exhaust leak. Normally if you're just replacing O2 sensors, you replace the upstream ones first. It's the downstream one that's telling you the cat is bad. Normally they don't really wear out because if the cats are working, it's pretty clean and simple back there. The upstream ones are the ones doing all the work most of the time as they're the ones switching back and forth all the time. When the rears match the front, that means the cats aren't doing anything. I think it's juts unlikely that the downstream O2 is bad. Usually when O2 sensors go bad, they get lazy and don't switch as quickly, not likely to go from a simple steady state to switching the same as the upstream one. You should get a code scanner and read the live values of the upstream and downstream sensors.

 

[mehullica]

You need a bank 2 cat. The one by the radiator.

 

[Trav]

Originally Posted By: slacktide_bitog
P0430 is a catalytic converter code, not an oxygen sensor.

However, you should replace all the o2 sensors when replacing the cat.


^ +1!

Toyota run tight cat efficiency perimeters, it doesn't take a large reduction to trip a P0420/430. For a vacuum leak on bank 2 I would expect a P0174, this can be quickly identified by checking the fuel trims, high + numbers indicate the ECM is adding fuel due to a reported lean mixture.

This year Toyota IIRC uses A/F monitors up front (AKA wide band O2) these are much more accurate than non wide bands and can monitor at WOT unlike the narrow band Lambda. The rears are standard monitors (narrow band O2).
An exhaust leak post front O2/AF monitor can cause some pretty weird or inaccurate codes and should be check for and repaired if detected before continuing further diagnosis.

The cats ceramic matrix is wash coated with precious metals that deplete over time to some degree and exacerbated by high misfire counts and rich mixtures (usually ignored CEL) or totally destroyed very quickly by constant misfires (flashing CEL).
OE cats have the most wash coat but if using aftermarket cats intended for use in CA/NY have more than 48 state versions hence they last longer before throwing the dreaded P0420/430 and carry a better efficiency warranty.
There is no effective way to clean a cat, the wash coat catalyst cannot be renewed from a bottle.

 

[Vikas]

My memory is failing but I recall I had heated argument with Trav (may be?) when *I* was the one claiming that catalytic convertor code in 99% means degraded catalytic converter and NEVER bad O2 sensor. Or may be it was somebody else but equally extremely well-respected BTOGr.

Back to the topic; google "O2 sensor extender" and get this monkey off your back.

AND yes, don't put cheap aftermarket converter. The code *WILL* be back before the next year. Guaranteed!

You need Mode $6 data to ascertain health of the converter. If it is just on the borderline, chemical solution might get to shut it up for short duration. That data will immediately tell you if the other converter is on the way out or not. Also if you do replace the converter and the light does go out, the data will tell you if the tests results are great( new OEM) or on the borderline (cheap aftermarket). Finding the decoder ring for the Mode $6 data for your make/model might be challenge though.

Trav,

Do fancy scanner decode the Mode $6 test results?

 

[Wolf359]

Originally Posted By: Vikas
My memory is failing but I recall I had heated argument with Trav (may be?) when *I* was the one claiming that catalytic convertor code in 99% means degraded catalytic converter and NEVER bad O2 sensor. Or may be it was somebody else but equally extremely well-respected BTOGr.

Back to the topic; google "O2 sensor extender" and get this monkey off your back.

AND yes, don't put cheap aftermarket converter. The code *WILL* be back before the next year. Guaranteed!

You need Mode $6 data to ascertain health of the converter. If it is just on the borderline, chemical solution might get to shut it up for short duration. That data will immediately tell you if the other converter is on the way out or not. Also if you do replace the converter and the light does go out, the data will tell you if the tests results are great( new OEM) or on the borderline (cheap aftermarket). Finding the decoder ring for the Mode $6 data for your make/model might be challenge though.

Trav,

Do fancy scanner decode the Mode $6 test results?


Well looks like Rockauto just sells the non CA ones and those are in the $200-250 range. They come with a 25k mileage warranty and a 5 year/50k structural warranty. So it'd probably last at least a couple of years. In theory, by the time it goes bad again, it should be time to get rid of the car.

 

[Vikas]

$250 vs $2.50 but it is your call!

 

[The Critic]

As the others have mentioned, you need a new catalytic converter. The sensors are almost never the cause of P0420/P0430 faults on Toyota's.

Lucky for you, the OE cat's are quite reasonable in cost.

 

[slacktide_bitog]

Rockauto has Pacesetter manifold converters for your Highlander for about $150 each. The rear cat from Walker is also around the same price as well.

Pair them with Denso or NGK/NTK oxygen sensors