Bought a First Gen, Everything is perfect except

Oh, and advice:

You can do these sensors on your own. If you live in the rust belt, treat the sensors after driving and getting things hot, quench the sensor base with Kroil or PB or similar, day in and day out, a few times before starting.

Get an "O2 sensor wrench", which is an attachment for your ratchet/breaker bar, which is pivotal.

You may also need to buy a reamer/O2 bung thread cleaner.

You may need a gasket for each sensor, I'm not as familiar with the V6/4.0L VVTi engine.

If replacing the O2 sensors doesn't solve your issue, don't fret. The stealership is probably throwing everything and the kitchen sink at it: New manifold, new manifold studs, cats, O2 sensors, etc. Basically anything that could be wrong. But the fact you're saying it's running like shit, like it's in limp mode, tells me either (A) it's probably the upstream sensor on bank1 (b/c P0420 is bank 1) reporting fucked up values which could be causing misfires or (B) you may actually have a bad coil causing bullshit combustion, but I'd expect other symptoms and/or codes.

 

Shifty - holy hell thank you. This is amazing stuff and I truly appreciate it. I’m going to heed your advice and light as well replace all the sensors while I’m replacing one. I’ll also check for leaks / cracks / issues with the manifolds. Hopefully it’s just the sensors. I don’t know enough to know what I should do if it’s not, but I’ll certainly start there with the 400 option rather than thousands

 

thank you. I personally do not think it is running like shit, the dealer was saying it just is a little more bogged down than it should on the top end. It doesn’t have the most power, no. But I really just like to cruise in it and don’t need it to run a 1/4 mile. I appreciate the tips on DIY. That’s my plan. Just built a little shop, time to put it to use.

 

Good info Shifty! Always start with the cheap stuff first

 

As stated, grab the 3 knobs and pull them outward, there is a phillips head screw behind each of them.
Dont forget to push the AC vents upward, this uncovers 2 more phillips head screws for the radio bezel.

 

You would need to look at the tacoma to find that, they did produce the 05-06 tacoma 4wd with an RA60 6speed, weird i know. I think i have seen a Tundra 4wd 4.0 manual regular cab base model work truck once but the Tacoma was way more common to see a manual 4wd. (they were not very common)

 

:sigh
Stealerships....
That engine has 4 cats if i remember correct, one on the back of each manifold, and two in the downstream pipe before the muffler. Maybe one is a resonator but i vaguely remember it having 4 cats.
The stainless manifolds on the 4.0 1GR-FE are paper thin and you can literally hear the exhaust valves open and close if you listen in the fender well, or parked next to a wall with it running. The biggest thing is the 4.0 from 2005-2006 era is tuned for 100% gasoline, as there was nowhere with ethanol blend back then. Now that your vehicle has been running ethanol blended fuel for the last 15 years or so, the volume of ethanol blended fuel is totally different from what the ECU was tuned for using 100% fuel. Its quite possible the cats are stopped up with 200k+ miles. My Tundra has the 2UZ-Fe v8 engine and one of my cats stopped up and blew out the exhaust pipe, blew out a silver dollar sized hole in the exhaust pipe in front of the cat. I was riding down the highway pulling a trailer with the radio going and climbing a hill my interior cab noise went from moderate/normal to "BLAAAAHHHHHHHH" instantly like my muffler fell off. I stopped immediately and jumped under the truck because the noise was clearly coming from the passengers side right by the floorboard, so i hopped under it and sure enough a huge hole blew out in the exhaust pipe. The cat apparently got stopped up enough that it restricted air flow, and while i was towing the exhaust gas temps were so high it melted the pipe and the exhaust gas found a way out on its own.

You have a few ways to fix this
1) watch the videos online of people washing their cats out, hot water, pressure washers, ive seen people blow tons of black goop out of the cats, this is a cleaning process i guess in places that have strict emissions and tests
2) find a lower mileage wrecked truck and buy the exhaust manifolds off it and swap them around
3) buy some headers and get the O2 simulators that cut the check engine light off (i did this on my tacoma with the 4.0)

If the cat or cats are stopped up, the exhaust gas has to get out somewhere. Before mine blew a hole in the exhaust pipe, i noticed the tail pipe wasnt getting a ton of air, and i could hear an exhaust leak up on the manifold starting about a week or two earlier. I just stayed low in the RPM and low throttle and figured i would pull it apart soon. Since the cat stopped up, the exhaust gas cant get out the tail pipe so it creates a way to get out and you might be hearing an exhaust leak up on the manifold. Then again you might simply have an exhaust leak at the manifold and its allowing fresh air into the exhaust system, and the 02 sensor is picking up the extra air and thinks something is wrong (hence the CEL)

 

I’m going to be in the minority and say if your only code is P0420 you will be replacing your cats at some point soon. Certainly one should check other components.

I know on 01’s and 07’s you can change all kind of bulbs on the back of the instrument panel. They are not soldered in, especially the gear indicators.

 

That typically hasn't been the case with the 1st gens. Maybe a 2nd gen thing?

 

Just wanted you to know it was in fact the dimmer switch causing my dash lighting issues. Tried replacing bulbs first, then found a switch on eBay and that did the trick! Thank you!

 

Heck yeah man! Glad you got it fixed

 

The experts have already weighed in, but I'll second their advice. I went down this road with a 2004 4R throwing the same code (same 4.0L v6). I replaced the cats with aftermarket at $800 in parts only to find that the codes came back. I replaced all four 02 sensors and the MAF next using the Denso part numbers, procured through RockAuto. Here are the part numbers I used (possibly different for your truck, these are the 04 4R), it highlights the differences -- two upstream were identical, R/L downstream were different. They were not hard to swap at all (especially compared to doing the cats).
Denso 234-9047 for both upstream A/F sensors
Denso 234-4805 downstream right
Denso 234-4804 downstream left

$86 Denso 197-6030 Mass Air Flow Sensor

Denso 197-6030 MAF

 

Are those part numbers for your 2020, or his 2005? www.densoautoparts.com is showing totally different numbers when I plug in his truck details. Important we're giving OP valid info so he doesn't blow his $$ on parts that won't fit.

​

 

So changing the MAF is probably what I should do next I guess. I've done cats and all 4 Denso O2 sensors and still get p0420 and p0430 sometimes. I even got O2 spacers.

 

Sorry Shifty, those part numbers are for my 04 4R -- I was trying to highlight that the upstream and downstream are different, and right/left downstream were different (not four of the same thing). I found the same AFR you did, but came up with a different part for the 02. I chose a 2005 Toyota Tundra Base, 4.0L V6 on Denso's site. I get these part numbers on RockAuto as well looking up that vehicle.

Upstream AFR (both sides) is Denso 237-9026 (https://www.densoproducts.com/denso-234-9026-oe-identical-afr-sensor)
Downstream O2 (both sides) is Denso 234-4260 (https://www.densoproducts.com/denso-234-4260-oe-identical-oxygen-sensor)

Both parts are available for slightly less at RockAuto (I mention them because I've had good experiences there. I have never received counterfeit parts.)

 

Try cleaning it first...I've never actually seen a MAF fail, but I usually replace them around 200K anyway.

 

I already tried that. Trucks got 350k miles.
I don't see a Denso MAF on Rockauto for an 03 2uz though. I wonder what brand I should look for?

 

Denso's part lookup tool (screenshot above) disagrees with the numbers you pulled from RockAuto.

Are you sure you were looking up for the V6, and not the V8?

EDIT: Shit, you're right, I accidentally circled the universal, which OP should not use. I'll mark up that pic so I don't confuse anyone. Fuck!

 

Hitachi is OEM for the V8 / 2UZ-FE on MAF.

Denso appears to be OEM for MAF on the V6 that OP has in his truck.

 

Yup our OEM MAF sensors are Hitachi not Denso.

 

I had the same "tick" even after putting on headers and making sure there were no leaks. If you end up replacing the manifolds and still hear it, don't be concerned, our injectors make a ton of noise.

A new shaft seal will definitely quite the cab noise, though.

 

Got both P0420 and P0430 codes. Gonna try the downstream sensors first. Denso 234- 4260 x2. Wish me luck.