P0420 and P0430 codes (1 Viewer)

[drewdub]

Greetings, I have a 2005 GX470 with 105k. I bought it about a year ago, since then done brakes, timing belt, water pump, replaced all fluids. I have a few things left to tackle (driveline clunk, leaking axle boot, driver's door lock actuator).. but I want to address CEL/VSC, etc lights.

I bought a OBD II Bluetooth scanner and it is pulling P0420 and P0430 codes. I am curious what is the best course of action, I don't have to worry about actual emissions (no testing in Michigan), I just want the codes gone. Based on what I am seeing it appears the best order of operations is: 1) look for leaks in exhaust; 2) replace O2 sensor(s)?; 3) I have seen the o2 sensor bypass or whatever that sells for $150 and seems to fix this issue on Toyotas?

What would anyone here recommend? I want it fixed but I don't want to throw money down the drain.

Thanks a lot

 

[mercedeezel]

welcome, some folks have had luck by simply replacing the gas cap. however, i'm not sure if their codes were what you're scanner is reading. I'd try that 1st. For me, it was the bypass kit that worked.

 

[drewdub]

The gas cap has been replaced, and I think that is a separate EVAP related code. These codes pertain to "catalyst system efficiency below threshold"

If I go the bypass route - should I replace the O2 sensors first?

 

[blakewhisenant]

You might look at the air injection pumps too. I dont have an 05... but I am pretty sure those can toss a code the is emissions related. If not that its the Cats.

 

[BlackCat]

The gas cap has been replaced, and I think that is a separate EVAP related code. These codes pertain to "catalyst system efficiency below threshold"

If I go the bypass route - should I replace the O2 sensors first?

Lol, ya. A gas cap isn't going to fix those codes.

 

[GXO]

O2 sensors for sure. Error should tell you which to do. Bank 1 is passenger side. Sensor 1 is pre-cat. Bank 2 is DS. Sensor 2 is post-cat.

 

[taco47001]

Replace all 4 O2 sensors and then drive the vehicle. Once you replace all four the ECU must recognize a certain sequence of vehicle operation for it to determine a pass or failure of the emissions system. I'm not exactly sure what the sequence is but a casual drive at varying speeds of 35-50mph for a continuous 15-20 mins should do the trick.

The codes are simply a result of a difference in the readings between the pre-cat sensor and post-cat sensor. O2 sensors don't last forever and recommended replacement interval by most industry standards is around 60k miles. At 105k they are probably due and ultimately what's causing the codes.

 

[BlackCat]

Replace all 4 O2 sensors and then drive the vehicle. Once you replace all four the ECU must recognize a certain sequence of vehicle operation for it to determine a pass or failure of the emissions system. I'm not exactly sure what the sequence is but a casual drive at varying speeds of 35-50mph for a continuous 15-20 mins should do the trick.

The codes are simply a result of a difference in the readings between the pre-cat sensor and post-cat sensor. O2 sensors don't last forever and recommended replacement interval by most industry standards is around 60k miles. At 105k they are probably due and ultimately what's causing the codes.

I've worked in the "industry" for almost 15 years and never worked for a manufacturer who called 02 sensors or air fuel sensors maintenance items. My GX has its original 02's with 150k and my Infiniti has its originals with 210k.

 

[GXO]

Replace on failure. That is why they have a specific code. Either way, swap em out!!

 

[taco47001]

I've worked in the "industry" for almost 15 years and never worked for a manufacturer who called 02 sensors or air fuel sensors maintenance items. My GX has its original 02's with 150k and my Infiniti has its originals with 210k.

I'm not saying they should be maintenanced like greasing U-joints, or re-packing wheel bearings every 30k, I was simply offering that while they do normally last quite a long time.....they are an item that can require more attention than "change it when it breaks". Do you only clean your MAF when your truck throws a code? I'm not trying to say change the O2 sensors every 60k but when one faults...IMO, it's usually better to just replace all at once. Admittedly I am no ASE certified mechanic and maybe I'm dead wrong...I'm ok with that. I've had the same codes thrown in my Tacoma, my LX470 and my wife's GX I just bought. Changed all 4 O2 sensors at the same time....and oila', no more code and life is peachy.

 

[BlackCat]

I'm not saying they should be maintenanced like greasing U-joints, or re-packing wheel bearings every 30k, I was simply offering that while they do normally last quite a long time.....they are an item that can require more attention than "change it when it breaks". Do you only clean your MAF when your truck throws a code? I'm not trying to say change the O2 sensors every 60k but when one faults...IMO, it's usually better to just replace all at once. Admittedly I am no ASE certified mechanic and maybe I'm dead wrong...I'm ok with that. I've had the same codes thrown in my Tacoma, my LX470 and my wife's GX I just bought. Changed all 4 O2 sensors at the same time....and oila', no more code and life is peachy.

I've never cleaned a MAF sensor on any car I've owned either. The logic about replacing all of them when you get a code for one doesn't make sense to me either. Do you replace all 4 tires if you get a nail in only one? Do you replace all the glass in the truck if you crack the windshield?

 

[GXO]

I would (and have) replaced both pre-cat O2 sensors and do tend to replace them in pairs as they ones pre get a lot more abuse.

Other than that...they aren't that hard to replace with the right tool, which I bought, so it is not something I stress over

 

[sledge916]

I had this code as well, nothing I did got rid of the code except replacing the cats, and I replaced everything under the sun first, once I replaced the cats the light stays off for good. I used Lexus parts.

Seth

 

[GXO]

My cats/manifold are up for next year...along with the starter, water pump, timing belt, and some gaskets and such. Fun fun!

 

[drewdub]

I would (and have) replaced both pre-cat O2 sensors and do tend to replace them in pairs as they ones pre get a lot more abuse.

Other than that...they aren't that hard to replace with the right tool, which I bought, so it is not something I stress over

And what is the right tool?

 

[GXO]

Sears.com in the right size.

 

[Bull Moose 100]

Denso Highly Recommends that you replace both downstream or both upstream at the same time. Failure to replace them in pairs can cause an imbalance in the engine fuel management system resulting in poor fuel economy and possibly damage to the catalytic converters.

 

[GXO]

Denso Highly Recommends that you replace both downstream or both upstream at the same time. Failure to replace them in pairs can cause an imbalance in the engine fuel management system resulting in poor fuel economy and possibly damage to the catalytic converters.

Yep! I replaced all 4 at once last week and I am already seeing a serious improvement. I disconnected the battery while I swapped them to force an ECU remap with the new sensors (30 min or so with terminals pulled will do it).

 

[intoodeep1113]

Yep! I replaced all 4 at once last week and I am already seeing a serious improvement. I disconnected the battery while I swapped them to force an ECU remap with the new sensors (30 min or so with terminals pulled will do it).

What sort of serious improvement are you seeing?

 

[GXO]

What sort of serious improvement are you seeing?

I'm still on the fill from Friday. It takes me a while to burn this much gas (54 gal). Right now I am at 140 miles or so and the main tank is full and the aux just drained a bit into it. So I am just getting into the burn phase. Aux tank life is weird.