My 2009 Tacoma has 48000 miles and runs great, but recently the check engine light came on. The dealer says it is a P0333 code which is a knock sensor, and apparently refers to the electrical resistance values. They looked and said it is either critters chewing on the wiring, or the sensor itself is bad. It is so buried in the engine that it is impossible to see, or so they say. It costs $2,000 to fix if it’s the wiring, or $4,000 if the sensor since they have to take the head off the engine. As I said it runs great, no knocking. My only solution is to ignore the light and buy a code reader because otherwise if something else goes wrong I would never know. Any better ideas out there?
Other than looking in all the nooks and crannies under the hood for a mouse nest…sounds like a plan…
;-]
A more practical solution would be to go to a well-reputed independent mechanic.
For a competent mechanic, this isn’t “rocket science”, and a solution would surely cost FAR less at an indy shop, as compared to a dealership.
If you Google " How do I replace a 2009 Toyota Tacoma knock sensor?" you will wind up at a Tacoma forum where they discuss using a mid 80s Chevy truck knock sensor which only costs $50 and works better.
I am not suggesting you do this yourself but seek out an independent mechanic or a local Tacoma enthusiast to do it for you.
Remove the head to service the knock sensor? That seems unlikely. I think they mean they have to remove the intake manifold and throttle body. It’s probably a big job to get at it, but not nearly as time consuming as removing the head.would be
For the 2tr-fe engine (2.7 L) on the 2wd version of the Tacoma, I’m seeing a little under $250 for the oem part, and about 2 hours labor to replace it. If you had the sensor on the bench it would be easy to test the resistance to see if it is the sensor itself that is bad (spec’d at 120 to 280 k-ohm , room temp) . But that might not be so easy to resistance test the sensor when it is already installed.
One note, if your truck is configured as above, the prices you are being quoted seem a little on the high side. How did you come across this shop? Does it have good recommendations from one of your friends, co-workers, fellow church goers, etc? If not, suggest finding an inde shop that way, and getting another quote on this job, or two. You don’t need a dealership for this job, an inde shop, one preferably that specializes in Asian cars, would be a better and more cost effective choice in most cases for a 2009.
The problem with ignoring it, is first, the engine may indeed be knocking a little, but you don’t hear it. That could shorten the lifespan of the engine significantly. Second, the computer might reduce the available engine performance if it thinks the knock sensor is bad, so you’ll lose some acceleration you used to have. And third, like you say, you won’t be able to tell if something else goes wrong that needs immediate att’n, b/c the CEL is on all the time. If you live in an emissions testing date, that may be a problem too. Suggest to get a few more quotes before adopting the wait and see approach. The wait and see method may be what you end up doing, and might well work for you, but it carries some risk and inconvenience, so that isn’t what I’d do myself if I had this problem.
P0333, Knock sensor #2 circuit high. This only applies to the V-6 engine, the four cylinder doesn’t have a bank 2 sensor.
The Toyota instructions state to remove the engine from the vehicle, then to remove the cylinder heads to replace the knock sensors. If GM knock sensors can be installed without removing the cylinder heads that would save a lot of time.
The labor to replace the knock sensors is 18.7 hours. I think the first step should be to remove the intake plenum and manifold to inspect the wiring for damage. Damaged wiring can be repaired, unless the damage is excessive there should be no reason to replace the engine harness.
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Wow, that is absolutely terrible sensor placement. Engine removal and 18.7 hours labor! 
Much like a Dentist filling a cavity from your hind end!
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For the 1gr-fe 4L engine, Nevada’s comment is spot on, the entire engine ass’y must be removed to replace the knock sensor. More bizarre than even having to remove the engine for a sensor replacement, the cylinder head must also
be removed.
I’m seeing 15-23 hours labor for one sensor, depending on the specific configuration of the truck. The higher labor number is for the X-runner version of the vehicle.
Given this information – and assuming this is the 4 L engine version of the truck – I think the OP’s suggestion to just ignore it might be the best way to go. Even if doing so eventually ruins the engine. Probably cheaper to just wait until that happens then replace the entire engine. And there’s a chance there will be no engine damage at all even with a defective knock sensor due to the way is which the computer handles the situation, so OP can ride that potential upside as well.
If I had this problem and wanted to spend money on it, I’d spend a little investigating if it was just a wring problem, something amiss between the computer and the sensor connector.
Now I know about this, should I ever feel in the need to buy a Tacoma, it will be one w/ the 2.7L engine version.
The person or people who decided that location for the knock sensor was a good one should be located and given the raspberries! 
Now that I know this, if they ever start selling Toyotas around here, I’ll run the other way! 
CSA
I’ve always said that car engineers (after 5 years on the job) should be forced to go to the dealerships and ordered to work on the stuff they designed under the warranty flat rate system for a few years.
It’s sheer idiocy to locate knock sensors in locations like that.
If for some reason a GM sensor can be used without much difficulty (I don’t see how…) then that’s what I would do. All a knock sensor is is a Piezo microphone much like those used to amplify some acoustic guitars.
What the OP could do is get the engine up to operating temp on a hot day, find a steep grade, and punch it hard while going uphill. If there is no rattling from the engine they could possibly ignore the problem.
For 4 grand or more that would be my option if faced with something like this.
Another idea, might work, just buy a new sensor and glue it on the block in some accessible place where you’d expect knocking sounds to be broadcast from inside the engine, w/some JB. Connect it to the other sensor’s connector. Good chance this won’t work, but when you’re looking at the expense of 20 hours labor …
Good idea, as this will cause the check engine light to go off, and enable the car to pass inspection.
Edit: even simpler is to splice a resistor of the proper value in place of the sensor.
“…My only solution is to ignore the light…”
Here in Maryland you would fail emission testing. They wouldn’t even test your car with an engine check light on.