P0420 and P0430 - 2006 LC

[looking4lc]

The color of your old sensor looks contaminated, what color coolant are you using as it looks green, or have you been using a fuel additive. Sensors normally fail and stick at a voltage around 0.450v so I would look a little deeper into it.

Thanks Julian
Coolant Toyota red, and yes i used fuel additive few times

well this is driving me crazy, i am trying to use obdII scan tool to get the reading and see where the problem is. Lots of people saying if you replace the Front sensors, engine light will be gone however mine shows up every 300-400 Miles so, even if i replaced both fron sensor, i wont be able to see if that solved the problem till after awhile.Now i see the code in OBDII as "Pending" P0430 Blah

 

[Chance]

apparently front Sensors called " Air Fuel Ration" Sensor and not O2 Sensor. went today to replace the front and i bought the wrong items. Sucks

Denso part # 234-9051 for lx 07

and i got 234-4260 , does anyone know what this is for? i know they are O2 sensors but are they for the one in the back?

if i can use them in the future i dont need to return them since i live overseas.

Thanks

Damn! I have 4 "O2 sensors" sitting ready for me to put in tomorrow, supposedly 2 Upstream and 2 downstream. They have the same part number but when I pull them out of the box the plug-in looks different on the upstream versus the downstream, but none are like the air fuel sensor you posted. I guess I'll replace the downstream ones and pull one of the upstream ones to see if it looks like the one you pulled or like the ones I bought. I have an 07 LX

 

[looking4lc]

Damn! I have 4 "O2 sensors" sitting ready for me to put in tomorrow, supposedly 2 Upstream and 2 downstream. They have the same part number but when I pull them out of the box the plug-in looks different on the upstream versus the downstream, but none are like the air fuel sensor you posted. I guess I'll replace the downstream ones and pull one of the upstream ones to see if it looks like the one you pulled or like the ones I bought. I have an 07 LX

whats the part number you got?
i was wondering if the 234-4262 can be used with lx 07

 

[Chance]

All 4 of my O2 sensors say 234-4260, but the upstreams are different from the downstreams not to mention the upstreams were more expensive. I bought all 4 from partsgeek

 

[Chance]

I found this on another thread regarding part numbers Oxygen Sensor (O2) Part Numbers and Replacement

 

[Chance]

I found this on another thread regarding part numbers Oxygen Sensor (O2) Part Numbers and Replacement

 

[looking4lc]

I found this on another thread regarding part numbers Oxygen Sensor (O2) Part Numbers and Replacement

i found lots of thread talking about this issue and most of them got it solved by cleaning/replacing the air filter or changing the pcv valve. i checked my air filter and it was dirty, today i will try to replace the pcv valve.

 

[Chance]

I replaced my air filter, I guess next will be the pcv valve then. I'm changing the air fuel sensor tomorrow.

 

[looking4lc]

I replaced my air filter, I guess next will be the pcv valve then. I'm changing the air fuel sensor tomorrow.

when does the check engine light come back after you reset it?
are you changing both Air fuel sensors or just bank 2 ?

 

[Chance]

It comes back on after the first drive that I took. About 7 miles(I'm on cal this weekend and had to drive to the hospital). I changed out the downstream O2 sensors today and pulled the drivers side upstream(air fuel) and saw the same type of sensor that you did. I reinstalled it and I'm going to get the right part Monday morning. The passengers side(bank 2) of im correct, upstream sensor was a little tricker to get to and I had to spray some pb blaster on it. I'm going to replace it Monday as well. Now my LX is throwing the p0420 and p0430 as well as P2197 and P0174. So dang aggravating. Hopefully changing the upstreams out will clear up the issue.

 

[looking4lc]

It comes back on after the first drive that I took. About 7 miles(I'm on cal this weekend and had to drive to the hospital). I changed out the downstream O2 sensors today and pulled the drivers side upstream(air fuel) and saw the same type of sensor that you did. I reinstalled it and I'm going to get the right part Monday morning. The passengers side(bank 2) of im correct, upstream sensor was a little tricker to get to and I had to spray some pb blaster on it. I'm going to replace it Monday as well. Now my LX is throwing the p0420 and p0430 as well as P2197 and P0174. So dang aggravating. Hopefully changing the upstreams out will clear up the issue.

can you point out which one the downstream and which is the upstream?
which sensors did you replace with the one you currently have? (234-4260)

Thanks

 

[Chance]

can you point out which one the downstream and which is the upstream?
which sensors did you replace with the one you currently have? (234-4260)

Thanks

So, I replaced the 2 downstream o2 sensors, which is the part number you referenced and today I picked up the upstream O2 sensors and replaced them. I cleared the codes and went driving. The passenger side upstream looked a little fouled(I'll post a picture of both upstreams), so I thought I had fixed it. Well, after driving for about 20 min the check engine light came on as well as the vsc lights. I checked what codes and it was still p0420 and P0430. I guess after your suggestion, I'll move on to the pcv valve. Not sure what to do if that doesn't work. I guess a cat bypass since I'm in a non emission state.

 

[Chance]

First pic is the upstream o2 sensors with the one with the carbon build up being the passenger side. Then the next two pics are the part numbers for the downstream and upstream o2 sensors.

 

[Julian Stead]

The P0174 code does make sense with the issues your having, this means that there is to much oxygen going to the upstream oxy sensor, The P0420 means there is to much oxygen hitting the downstream sensor. Both point to the engine running lean or a exhaust leak, the sensors involved in the fuel strategy are TPS, Coolant temp, upstream oxy sensor, and air flow meter. What mechanically could affect this is a vacuum leak, misfire(for whatever reason), fuel pressure(maybe fuel filter), compression, valve timing, throttle body and exhaust leak. Additional things that could affect this are Air pump or EGR if fitted.

Ps. Air filter also.

 

[Chance]

The P0174 code does make sense with the issues your having, this means that there is to much oxygen going to the upstream oxy sensor, The P0420 means there is to much oxygen hitting the downstream sensor. Both point to the engine running lean or a exhaust leak, the sensors involved in the fuel strategy are TPS, Coolant temp, upstream oxy sensor, and air flow meter. What mechanically could affect this is a vacuum leak, misfire(for whatever reason), fuel pressure(maybe fuel filter), compression, valve timing, throttle body and exhaust leak. Additional things that could affect this are Air pump or EGR if fitted.

Ps. Air filter also.

Thank you for the advice and knowledge. I'm a 1/2 mechanic working my way up. Here are all the things I've done:

1.checked to make sure thermostat is working. Engine coolant is measuring between 190-193 once up to temp, so it seems to be working

2. Changed air filter

3. Cleaned MAF

4. Changed down stream O2 sensors, that's when I started getting the other funky codes along with P0430 and P0420.

5. Changed the upstream O2 sensors. Now back to just P0430 and P0420

6. No ticking as described by LC100
In a previous post for air leak.

7. The dealer I bought the LX from had purchased the AIP bypass kit, so I installed that also.

I'm going to read up on TPS you mentioned. Showing my ignorance, I don't know what that is, I'm assuming something with the throttle. The vehicle seems to be running fine, idles fine. I'm also going to read up on the mechanical things you mentioned and how to evaluate/address those issues. I really appreciate the advice and I am following what y'all say. Thanks in advance for anymore information/help.

 

[Chance]

I'd sure like all the old OEM parts, I could stock my shop.

@Julian Stead, they seem set on throwing parts at the issue, regardless of anyone's suggestions.

I'm not just throwing parts at it. I'm trying to work thru it. I should have posted earlier and told you thank you for your suggestions. I checked most/all of the things you suggested that I knew what/how to evaluate. The things with the VVTI I need to look into, but I was hoping it was something "easier" as those things seem out of my scope of knowledge. I need to look into them though. I posted a reply to Julian and you can see everything I have done up to this point. Any suggestions will be appreciated and believe me I'm heeding yalls advice and following it. As a side note, if you would like my old O2 sensors, I can mail them to ya

 

[looking4lc]

i had p0430 only and it seems the issue was solved with cleaning the air filter.
Bought pcv and will be replacing it tonight. I hope it will solve my little low idle.

 

[KYLandy]

subbed for outcome.

Got the same codes right now but I think the problem is the E85 gas I put in. See this thread for details of my stupidity.

 

[Colorado80]

Update:

1. Ordered the correct oxygen sensors (ordered wrong ones last time)
2. Configuring techstream to read live data
3. Ordered new PCV
4. Thermostat on order with new gasket (OEM)

Will keep everyone posted as to the outcome of this. Also, the air filter is brand new so now breathing issues there.

 

[Colorado80]

Update:
Replaced all 4 of the sensors and still have codes being set.

As far as the comment earlier for just throwing parts at it, that's not really the case as the Toyota dealer diagnosed the problem as the catalytic converter. After they were replaced, the lights were still on. Given the incompetence of the dealer I think I should just take it on myself.

Next up on the list:
1. PCV
2. Thermostat

After that . . . no clue.