Don~
Yep. Right on the money. 100K is the expected lifespan of the heated air-fuel/oxygen sensor.
It's a fairly straightforward remove/replace IF you don't have a heavily rusted exhaust manifold and the unit isn't seized in place. It is the front, driver's side sensor throwing the code. If you can change out spark plugs, you can do this and save yourself some $$$. The major portion of this bill at the dealer is labor. I've removed and reinstalled all four of mine just to inspect and get a good application of anti-seize on them.
Note that when one side goes, the other side is probably not far behind.
I strongly suggest you replace both banks while you're already under there. Why pay shipping twice? My $0.02.
For your 2001 Tundra V8 SR5 4X4:
Here is the sensor you need:
Denso, #234-4169.
RockAuto.com has em for about $60. Both sides take the same one. (first pic, below) Resist the impulse to try a cheaper aftermarket or other brand part here. This is an ECU-related component, and you'll have problems, guaranteed. I'd also steer clear of the "universal" models that require you to resplice the wiring into the old connector. Just to save a few $$$? On a component that should last another 100,000 miles?
You will also need a specialty socket like this:
Sparkplugs.com It has a cutout to allow you to work around the attached wires. Your local auto parts supply should have one in stock. There are a couple different styles. I've seen them at Harbor Freight for about $5 as well.
(fourth pic below)
The upstream sensors are located under the rearward end of the exhaust manifold, just forward of the exhaust pipe flange. For best access, lay with your head facing towards the front and reach back and over the front crossmember. I have a 2" lift and I don't even need to jack up the truck to do this. You can remove the skidplate to facilitate the procedure, although it isn't necessary.
(see the fifth pic below for a view of this sensor)
Give the base of the sensor a good soaking of PB Blaster, WD-40 or some other penetrating lube and let it sit overnight. As you are working at the exhaust manifold, I suggest you do the R/R on a COLD engine. It is also to make sure that the manifold is not in an expanded state from heat. Chilton suggests that if the sensor is hard to remove, you
might want to start and run the engine for a minute or so, shut it off, and try it again. Be careful! The sensor, manifold, and exhaust will all be HOT! Be
especially careful of the intake tube end of the sensor... the inside gets heated to
1500F!!
Then, the steps to remove and replace are:
1. Unplug the wire harness connector.
(It is gray, and will be up about 7" or so from the sensor. You might need to insert a small screwdriver to move the little retaining tab so it will slide out. Take your time here. It can be a little finicky. This part took me longer than the actual sensor to remove!)
2. Get the sensor socket on it and remove.
(This can be the trickiest part. A seized sensor is NO fun. Use the PB Blaster liberally. Unscrew the sensor, and if you get serious resistance, hit it with the lube, and then screw it back in. Do this a few times; it should work its way out. If it doesn't, I'd suggest letting the dealer or a trusted local shop do the work. Some people feel comfortable putting a breaker bar on it to get it loose, but it is my opinion that you don't want to be at home with stripped out manifold threads. If this happens, I'd bite the bullet and pick up some JBA headers and call it a day.
3. Apply anti-seize compound
(available at your local auto and marine supply stores, see pic below) to the threads of the new sensor. There are only about 3 or 4 threads on these units, so make sure to keep any compound away from the sensor's input ports.
4. Carefully start threading the unit in by hand. Take your time. They're in a position that is hard to see.
(Just like spark plugs, you do NOT want to cross thread these!)
5. Apply the sensor socket carefully to the sensor.
(Make sure you do NOT get the wires bound up!)
6. Torque to specs.
(14 ft/lbs. This isn't much. You can probably get 14 ft/lbs with one or two fingers on a standard ratchet.)
7. Reconnect the wire harness connector(s).
8. To clear the code (if any), either get a OBDII-compliant code reader or disconnect the
negative terminal on the battery for an hour or so to drain all residual system/ECU memory, reconnect, and drive. The code should be gone.
Done.
Do not skip the step of using the anti-seize. Sometimes you will get a package with your sensor unit. Sometimes not. A tube is only about $6.
Note that if you can get these done by yourself, when the time comes to do the same to the downstream (Bank 2) ones, they are WAY easier. They are a little more expensive; they run about $90 each. You don't need the O2 socket, but the TSM suggests you replace the metallic gasket and mounting nuts.
(second pic below, location view on the last pic below)
Also note that on some model years of 4WD Tundras, it appears that there are different specifications for the rear sensors than with the 2WD models, even from side to side. Crosscheck carefully to assure the right sensor for your truck.
* * * WARNING FOR CA EMISSION VEHICLES * * *
There is a specific downstream (Bank 2) sensor used on CA-only, V8 automatic transmission Gen-1 Tundras. It runs anywhere from $200-$225 at Rockauto.com. It
must be used on CA emission vehicles to work properly with the ECU/cat configuration. If you use the standard unit, it will throw a CEL code. As always, check with your dealer service writer or parts rep to verify the correct part for your model year application. (Just because your truck is IN California, doesn't make it a CA emission vehicle. It had to have been originally sold by a CA Toyota dealer.)
Let us know how it went for you.
* * * Note: If you're at 100K, maybe the dealer was recommending that you do the timing belt replacement (recommended by TSM at 90K). You don't want this to get too far past the due date; you're on borrowed time! The Tundra 4.7L is an 'interference' design, and when these go on our trucks it is BAD news...