P0420 and P0430 - 2006 LC

[OEMGUY0720]

Thanks Jerry. I already contacted the seller, no way I would cut and extend the wires of the O2 sensor for this, it doesn’t feel right, I’m returning this cat.

 

[2001LC]

You made a good decisions sending back.

This one on a VVT, I was told came out of NY.
Not sure but I think this is same one Fits 06-07 Lexus LX470 Land Cruiser D/S or P/S Front Main Catalytic Converter | eBay

 

[OEMGUY0720]

Yes thanks Paul @2001LC it really doesn’t look right and for the $$ and I still have to purchase parts and modify wires, I’ll pass I’m good. This is what I’ve seen that will work, everything bolt on including O2 sensor plug hole: DEC Catalytic Converter Fits: 2006 2007 Lexus LX470 4.7L V8 GAS DOHC | eBay

 

[landshark9]

My story goes a bit like this:
2007 LC 95,000 Miles, always highest octane available. CEL light/s came on and continue to do so within 10-15miles of reset.
P0104 MAF Confirmed
P0430 CAT Bank 2 Pending
P0420 CAT Bank 1 Confirmed

I have:
-Cleaned MAF
-Replaced MAF (oem)
-Replaced both rear 02 sensors (oem)
-Run CataClean
-Replaced Air Filter (oem)

Lights continue to come on...I've read all 17 pages of this thread. Any thoughts of where to look next? Vacuum leak? Other thoughts?

Appreciate it!

 

[2001LC]

This thread covers a lot! I don't recall if it covers two areas.
1) Fuel delivery. We've seen bad fuel, clogged fuel filter and faulty fuel pumps cause issues.
2) A.I. system issues. This is one I'm now looking at. I suspect, a failure of A.I pump filter and or impeller. This can blow debris into CATs.

Have you any other symptoms, issues or pending or stored codes or codes in the in last ~20K miles cleared?

 

[danimal24]

Make sure you check for exhaust leaks as well. That can trigger P0430/0420....

I am struggling with the same two codes. I will post my investigation results later for comment. Good thread on this issue!!

 

[danimal24]

In the spirit of making this a great thread and to get some help; here is where I am at on my P0420 / P0430 woes....

2003 Land Cruiser - Modestly modified (Bumpers, armor, lifted, 34" tires, well-maintained, up to date on services, etc.) Current mileage = 228k

Historically review:

Jan 2017 (199k miles): P0420 / P0430 came on and the following steps were taken

• Searched all over IH8MUD
• replaced all vacuum hoses under the hood (except charcoal related...driver's side rubber in engine compartment hasn't been touched)
• Replaced PVC valve
• cleaned MAF / Throttle body
• replaced fuel filter
• Note: pre-cat O2 sensors were replaced at 152k (pro-active)
• Replaced main muffler at 197k and noticed small leaks (exhaust condensation dripping at pipe flanges) - so replaced exhaust donuts...still slight leaks...

After all of this....still P0420 / P0430....

• replaced Post-cat O2 sensors...codes went away!!!!

Recently: P0420 / 0430 came back at ~ 225k miles

• Note that TB, coolant, H2O pump, heater Ts, spark plugs, etc all done at 217k miles
• Replaced intermediate exhaust cross pipe (from bank 1 to main muffler) and re-sealed all post cat exhaust flanges...(the only way to get them to seal and not leak water was by using exhaust sealer...)
• replaced pre-cat O2 sensors with denso...(code came right back). Old sensors were red in color...see picture at end. Is this normal or contaminated with red toyota coolant!?!?!? I can't find any good visual standards on the interwebs
• replaced valve cover gasket (leaking oil at gasket) and checked valve clearance (within spec)
• replaced fuel cap (needed a new on anyway
• Engine does not burn oil or coolant (coolant is topped off in radiator and expansion tank is always close to full at cold...)

After all of this still P0420 / P0430

Used Torque pro and tracked Pre and Post cat voltages (see pics below)...at idle post cat voltage is low (indicates lean / extra oxygen in stream). Torque pro also says "Rich to lean sensor threshold voltage Not Ok" for TID $01 CID$01 and TID $01 CID: $02...been trying to understand what that all means. This could mean intake leaks and/or exhaust leaks. Also need to check fuel trims to see if it matches.. (I think they should indicate Lean???)

Next steps:

1) Smoke test to check for intake / exhaust leaks. Is there an easier test to confirm / deny leaks?

2) Check fuel trims

Pics

Pre-cat O2 Sensor:

O2 Voltages at idle after load (top left is bank 1 Sensor 1, bottom left is bank 1 sensor 2, etc)

O2 Voltages at 2k RPMs (top left is bank 1 Sensor 1, bottom left is bank 1 sensor 2, etc)

O2 Voltages at idle before 2k RPM test (top left is bank 1 Sensor 1, bottom left is bank 1 sensor 2, etc)

O2 Voltages after load_coasting (top left is bank 1 Sensor 1, bottom left is bank 1 sensor 2, etc)

 

[danimal24]

Rich to lean sensor threshold error

 

[Julian Stead]

At Idle it is showing incomplete combustion, as in not enough fuel..Too much oxygen..

you’re better off looking at fuel trims and taking note the affect raising the RPM has.

 

[danimal24]

@

At Idle it is showing incomplete combustion, as in not enough fuel..Too much oxygen..

you’re better off looking at fuel trims and taking note the affect raising the RPM has.

thanks Julian Stead...that was the other thought I had last night...might be time for a fuel injector refurb??? truck runs perfect otherwise and always holds nicely at 190 deg. F

 

[danimal24]

so....I checked fuel trims...Long term and short term was hovering close to 0%...Bank 1 was slightly negative and Bank 2 was slightly high. Artificial vacuum leak and the fuel trims responded correctly (increased due to lean mixture)...i did not attempt a rich condition...would have had to grab the propane tank.. Also took infared temps pre-cat and post-cat. they were the same around 400 deg. F...I thought there should have been a slight increase...no temperature drop.

Any thoughts why my post-cat sensor is reading low voltage leading me to believe I have a lean condition? The fuel trims don't support this...

so below are some screen shots from Torque Output on o2 sensors and fuel trims. Left side is bank 1; right side is bank 2. From top to bottom is pre-cat O2 sensor, post-cat O2 sensor, Long Term fuel trims, and Short term fuel trims.

Readings at 2k RPMS

Reading at idle

Readings with artificial Vacuum leak

 

[danimal24]

Hey guys...so I did a ghetto smoke test on exhaust and intake (gatorade bottle, with black & mild, and compressed air) and got zero leaks...

so still stuck. I am contemplating just replacing the downstream sensors (again) or removing and cleaning injectors (professionally) and replacing all intake gaskets...

As a reminder; it doesn't look like i am loosing coolant, truck runs at 190 degs F, all maintenance is up to date (filters, plugs, TB, etc.). Still not clear why my downstream shows lean (low voltage).

My pre-cat sensors were "redish" when i replaced them...but not loosing coolant (thought it was contaimenated by toyo red coolant).

 

[danimal24]

Quick update for me.

I noticed that I had some condensation leaking between the exhaust flanges (post Cat connections)....where the donut is supposed to seal between the flanges.

So when i replaced the donuts during a muffle replacement; the flanges would pretty much bottom out against each other...so i guess the donuts did not fully compress.

I tried a new set of donuts. (aftermarket Bosal brand). Same issue...leaking water at start up.

So, i thought of buying OEM...but instead stacked two donuts and glued together with high temp exhaust sealant (copper based).

Installed them; ran it to temperature, and re-torqued.

I can say now that I am getting good post cat voltage readings and no faults in the vehicle test (rich to lean sensor threshold)...I still have a P0420 (but no more P0430); but waiting for it to clear up on own without clearing the Engine Light...

So; I will report back...doubling up the exhaust flange donuts made a better seal and have "fixed" the issue...I think!!!

 

[danimal24]

So the CEL cleared on it's own...I call it a success...

For me; the exhaust flange donuts were not properly sealing allowing air into the system and tricking the post cat sensors that the cats were not working.

If you see water dripping from a connection at cold start up; you have a leak. Fix it with new exhaust flange donuts...you might need to double them up. I have not characterized Toyota brand donuts...they might be thicker than aftermarket brands.

Cheers and good luck all with P0420 / P0430 codes...if your engine is in top shape and preventive maintenance has been done; it is not your cats...learn how to read your O2 sensors / fuel trims and don't give up!

 

[landshark9]

@danimal24 Still P0420/P0430 free?

 

[BullElk]

I am getting the same codes on and off in my ‘06. LX. I can hear a very slight exhaust leak that I need to get repaired. Perhaps that will cure my codes. I’ll see.

 

[danimal24]

@danimal24 Still P0420/P0430 free?

Landshark9....well....it came back, but noticed I have a leak where the two pipes merge before the muffler....I need to have it welded ...haven't had time to do that. Will report back when done!

Also fighting a driveline vibration at 70mphs! Always fun!

 

[2001LC]

I am getting the same codes on and off in my ‘06. LX. I can hear a very slight exhaust leak that I need to get repaired. Perhaps that will cure my codes. I’ll see.

Location of exhaust leak, is key, and can cause issue for sure. This is if exhaust leak before or near A/F ( forward on sensor VVT) or O2 sensors. A downstream of sensors leak, is not likely causing issue. Seem you could remove muffler, and not have this issue. Can't say I've tried this. But I have seen many muffler with large holes., never set off a DTC

 

[2001LC]

Landshark9....well....it came back, but noticed I have a leak where the two pipes merge before the muffler....I need to have it welded ...haven't had time to do that. Will report back when done!

Also fighting a driveline vibration at 70mphs! Always fun!

Close to O2, so worth a try.
BTW: I've seen, but never tried, a tape to repair exhaust pipe and muffler leaks.

 

[landshark9]

Borrowed a TechStream but way beyond my abilities, foreign language to me...Does anything jump right out? Still have a persistent PO420. All four sensors, new.