2018 Toyota Tacoma Double Cab, 3.5 L DOHC V-6 with variable valve timing, automatic transmission.

Several days ago, I went out in the Tacoma for several errands.
I knew something was seriously wrong as soon as it started, check engine light.
The truck ran like a Swiss watch the previous trip out in it.
Driving, it was in some type of "LIMP" mode, harsh/violent transmission upshifts, no power, about undriveable.
When I got back home, I plugged in my scanner and read the codes.
I cleared the codes, and restarted, instantly got another check engine light, and the same stored codes.

OK, it's a hard failure, not an intermittent, much easier diagnosis for a repair.

I crawled down a rabbit hole diagnosing the problem. I soon discovered that the knock sensor(s) and wiring and connectors for those sensor(s) are considered almost bulletproof.
The one noted problem is mice chew on the wiring, and soon I discovered a YouTube video that described my problem along with a potential repair resolution.
This is the YouTube video I found, and I used it as a helper. https://www.youtube.com/watch?v=SVtMoHSo_cQ&t=925s
I downloaded the video so I would have it available on my phone while working on the truck.
Metal buildings really kill cell signal and Wi-Fi reception.

I got a lift to the Toyota Dealership for buying the parts, I didn't trust the Tacoma, and it was raining that day, which ruled out my motorcycles.
While at the Dealership, I got a parts and labor quote at the Service Department. $1500+

All the parts were $300 and I did it at home myself. That included a set of spark plugs and oil filter for another day.
I figured out why the quote for them doing the job was so high.
Those Toyota Engineers packed 35 pounds of shit into a 5 pound bag!

The knock sensors are buried down in the "V" valley between the cylinder heads. Everything "topside" has to be removed just to see where you are trying to get to.

Throttle body.
Plastic upper intake manifold/plenum.
Aluminum lower intake manifold.
High pressure common rail fuel injectors and two high pressure fuel rails.
Mid-pressure port fuel injectors and two additional fuel rails.
Fuel pipes, fuel return loop back pipes, O-rings.
Multiple dozens of connectors, wiring, plugs, hoses, and clamps.
Plus about a half bushel basket of nuts and bolts.

Once you get all the above out of the way, then you can "maybe" see where you are trying to get to.

I did get the job completed tonight along with two road tests. I took the dog for a ride on the first road test, he was a good boy when I was outside working.
Six hours for the job, with several quick breaks for letting the dog outside to do his business.
The Tacoma ran like new again, and no check engine light.
The second road test? Straight to Lowe's and I bought a aerosol spray can of Tom Cat mice repellant.
When I returned home, I hosed down the engine and engine compartment with the Tom Cat spray.

Fucking Mice!

The next to last photo, yes that is the chewed wiring.

PXL_20260902_165352159 by cee_Kamp 32ACP, on Flickr

PXL_20260902_165709213 by cee_Kamp 32ACP, on Flickr

PXL_20260902_172829117 by cee_Kamp 32ACP, on Flickr

PXL_20260902_175925344 by cee_Kamp 32ACP, on Flickr

PXL_20260902_183224647 by cee_Kamp 32ACP, on Flickr

PXL_20260902_183234257 by cee_Kamp 32ACP, on Flickr

PXL_20260902_185755665 by cee_Kamp 32ACP, on Flickr

PXL_20260902_211517065 by cee_Kamp 32ACP, on Flickr

My Frontier had the knock sensor in the valley.

Is all that crap in the pink tray mouse nest debris? Is the vehicle garaged or kept outside? There seems to be a lot of 5lb bags carrying 35lbs of poo these days in regards to the automotive world. With more on it’s way by way of things like proprietary screw heads and legislation making it illegal for you to fix your own stuff.

Great rant! Great photos! Sorry for your trouble – you do good work.

quote:

Originally posted by Mars_Attacks:
My Frontier had the knock sensor in the valley.

I'm fairly certain all 'V' engines locate the knock sensors in that location. This Audi V8 is an example:

Little shits! I would be so pissed.

How long does your Taco sit without being run? I'm wondering how much time it took for them to nest and do the damage. If it were run fairly regularly, you'd figure they'd bail or get cooked.

I have a '16 Taco, but don't have too many issues with rodents in my area. I'm still thinking it may not be a bad idea to do the same thing with the mice repellant. I wonder how long it will last in an engine bay with the heat.

Great job doing it yourself. For me a less capable hands on guy, I had to have the dealership fix my Suburban once squirrels ate my wiring. Fortunately, rodent damage was covered by my insurance. I think I had to pay my deductible of 500. Squirrels are not the cute fuzzy citizens they appear to be.

Mice caused me a $285 repair on my mower. Four freakin cats outside but they can’t be bothered. Guess I’m feeding them too much.

Nice that you could do the work yourself, however tedious. I'm envy the skills. I'd have to shell out the big bucks to mine fixed if it came to it.

quote:

posted by nhracecraft: I'm fairly certain all 'V' engines locate the knock sensors in that location.

Most do, but some have or had them on the sides of the block. Still, some intake manifolds are easier to R&R than others.

At least you didn't have to pull the starter.

Some Toyota 8's have the starter located where your mouse nest was.

Boo!

Glad you were able to get it fixed.

I've had mice nest in my Ridgeline on the engine but under the plastic cover as well as in the duct at the cabin filter. But no damage other than shredding up the foam insulation under the cover and ruining a cabin filter.
I've since left the cover off and leave the hood propped open and haven't seen sign of them.

They've nested in the cooling channel between the shroud and engine in my ZTR 4-5 times. Some have recommended dryer sheets and peppermint oil to repel them. The peppermint oil didn't seem to have any effect and actually found they shredded up the dryer sheets for nesting material.

The Tacoma was my girlfriends vehicle. Before she was sidelined from ALS, she drove it to a bridge or highway construction jobsite every single workday.
Errands on the weekends, grocery store, hauling children, trips to the cabin, vacations, the Tacoma never sat still.
As her health deteriorated, the Tacoma started sitting.
It was common for the truck to sit, groceries were delivered to the house from Walmart. It was used for medical appointments and not much else.

Now that I have inherited the Tacoma, it is driven more frequently, but the mouse nest and wiring damage apparently was already done.

Yes, all the yellow/black debris in the pink plastic carry-all is mouse nest remains, extracted from the engine valley with needle nosed plyers.
There was also a significant amount of mouse nest debris sucked up in a shop vacuum cleaner, which I did not photograph.

The Tacoma is parked in an attached carport, next to my Jeep Rubicon. I have had mice get into the Jeep passenger compartment before.
This year seems to be a bumper crop of mice, and typically is a cyclic phenomenon.

As far as the location of the knock sensors, my past experience was with GM vehicles. Typically located at the engine cooling block drain plugs tapped holes, down near the engine oil pan side rails.
Back then, the engines had simple hex head pipe plugs in those tapped holes. When ECU controlled engines became a thing, the auto engineers removed a pipe plug on the assembly line, and screwed in a knock sensor on each side. Spark knock (pinging) typically takes place in the upper part of the engine between the piston dome and combustion chamber in the cylinder head.
It did make sense to me that the knock sensors got moved up to near where the pinging actually takes place vs sound/shock waves traveling all the way down to the bottom of the engine block.

And for what it's worth, I have never even heard a "crackle" of detonation (ping/spark knock) in the Tacoma, even when heavily loaded hauling tractors. So the more modern location for the knock sensors clearly works better than the old school designs, it just isn't any fun for the fixing/repairing of the more modern style/type, simply due to the location.

quote:

Originally posted by cee_Kamp:

As far as the location of the knock sensors, my past experience was with GM vehicles. Typically located at the engine cooling block drain plugs tapped holes, down near the engine oil pan side rails.
Back then, the engines had simple hex head pipe plugs in those tapped holes. When ECU controlled engines became a thing, the auto engineers removed a pipe plug on the assembly line, and screwed in a knock sensor on each side. Spark knock (pinging) typically takes place in the upper part of the engine between the piston dome and combustion chamber in the cylinder head.
It did make sense to me that the knock sensors got moved up to near where the pinging actually takes place vs sound/shock waves traveling all the way down to the bottom of the engine block.

And for what it's worth, I have never even heard a "crackle" of detonation (ping/spark knock) in the Tacoma, even when heavily loaded hauling tractors. So the more modern location for the knock sensors clearly works better than the old school designs, it just isn't any fun for the fixing/repairing of the more modern style/type, simply due to the location.

Knock sensors on the bottom of the block were almost useless, more so with non-variable valve timing (ie, pushrods). Knock will sneak up on you once you start playing with valve and ignition timing, having the sensor close keeps you from getting to that point.

If you think the 2018 has a lot of shit in it, you should work on a new one.

Stink bugs also like the PVC jacketed wiring. So much so that a cargo ship full of yota's got barred from entering Australia. They had to go to Japan, fumigate, then run them back.

mice delivered their babies in the A/C ducts of both of my Tundras. The first time to eliminate the smell the vent was switched from recirc to fresh air. That dumped the newborns into the spinning fan.

I declared jihad against all rodents when my first gen Tundra had the wiring eaten…twice!

I couldn’t destroy their pack rat homes or kill enough of them to ever get satisfaction.

I had something similar but not as severe happen to my Porsche a few years ago as the car doesn’t get driven in the Winter.

I won’t tell you how much it cost…

But my mechanic did recommend getting those glue traps placed all around the car while it sits in the garage. I’ve caught mice snakes and a bunch of bugs so they do work and are pretty cheap.

Get a cat, they love to hide under and on top of parked vehicles, and eat mice.

Heck of a job, doing it yourself at least you know it's done right, looking at that job half way though I'd have been cussing myself for not spending the $1200 in labor to get it done over the $300 parts LOL...

I needed to get back under the Tacoma hood today.
The black plastic upper intake manifold is set up from the factory with two different length sets of intake manifold runners, for low and high engine RPM. Each set is "tuned" for a specific RPM range.

On the very back of the black plastic intake, right next to the firewall, there is an actuator motor on/inside the intake manifold that flips an interior flapper valve back and forth for using both sets of intake runners as needed.
It's ECU controlled and switches seamlessly as RPM & engine load varies when driving.
Unplugging that actuator wiring plug was a challenge during engine disassembly.

I also couldn't clearly remember plugging that item back in during reassembly.
So today, I went and got a mirror on a stick from my toolbox and started looking. Yes, I forgot to plug that connector back in during the engine reassembly.

The real challenge was finding the dangling wire harness with a small plug on the end of the harness.
It was hanging down in the abyss near the transmission bell housing / engine block attachment joint.
I did find it, and plugged the intake flapper valve actuator wiring connector back in.

I was surprised that it hadn't puked up a check engine light and trouble code for the intake flapper actuator motor.
The damn mice got me again, the slight discomfort from crushed testicles while laying on top of the Tacoma engine will fade with time.

Good catch on the sensor before the code factory got busy.

I'm in the middle of replacing a timing chain on my Dodge.

Can't get the cover off without dropping the oil pan.

Can't drop the pan without removing the engine...

Good times.