Rodents ate my knock sensor !! 2006 toyota 4runner
Hi Everyone, i'd like to write this blog in case it helps someone that has the same issue I had.
During the pandemic we left to the countryside in the south of Chile. one day while routinely servicing my car i've noticed signs of rats or rodents inside my engine.
A week later suddenly my check engine light came on without a known reason so i scanned the car and got a P0333 code, meaning that bank 2 knock sensor has failed for some reason.
What is a knock sensor?
A knock sensor is like a microphone that listens to the piston knocking inside the engine and sends the information to the ECU so it can adjust the air fuel mixture correctly and prevent pre-ignition or knocking inside the cylinder, for example when you use low octane or bad fuel. without the function of this sensor you engine can premature early and carbon can build up around the piston and valves.
Back to our story
After scanning and seeing the p0333 code i was sure that this is related to the mice signs i was seeing every morning under the hood, i also investigated and discovered that this is a common problem since the cables of this knock sensor are made out of soy based material (WAT?) and aren't correctly insulated or protected.
Looking for a solution
the next morning i started searching for a mechanic who might be able to do the job. before that i read the service manual so i can understand the costs and complexity of the job. I called the Toyota dealership and spoke to their mechanics. Before that, I read in the manual that 2 gaskets need to be changed (lower and upper intake manifold), however their spare parts department told me that these gaskets do not exist in Chile and needs to be imported, So I ask the Toyota mechanic how are they going to seal the intake if there are no gaskets in stock? or would they use silicone gasket maker ? the mechanic reaction was: "there are no gaskets that's needed to be replaced for that job" and "the repair might be more expensive if we find more issues". that's when I realized i should probably do this job myself. Apart from that, since toyota didn't have the knock sensor in stock neither only the harness I had to pray that the mouse didn't chew those cables all the way to the sensor.
1/2 and 3/8 socket set with 10/12/14 sizes
T40 torx bit socket (only the socket, the allen style torx is useless for this job)
Allen socket set (I think it was size 8)
10/12/14 wrench, if you can get the flexible ones better.
Carburetor cleaner spray
tools for fixing the cables the cables: cables, soldering iron, soldering paste, electrical insulation tape and tubes. (voltage meter if you want to be extra en check the sensor but there's no reason for this sensor to fail becuase of a mouse chewing its cables, i didn't check and just repaired it and it was fine.)
rodent repellent spray (i'm not sure it works tbh but why not)
lots of light, headlamp, work lamp
remove the gas pump fuse and run the engine until it dies (this will remove all the fuel from the lower intake and will make it safer and less messy to work)
Disconnect and remove battery (this will also reset the computer)
Remove skid plate
Drain all the coolant to a 6 liter bottle (do this by opening the switch under the radiator)
Optional: remove the fan belt to prevent coolant from leaking on it and allow more work space.
So unfortunately, this knock sensor is located right under the lower intake, exactly in the lowest point of the "V" which means we have a lot of things to remove in order to get there.
Start with the air filter and throttle body, take a picture of everything before you perform any action , disconnect all hoses and sensors necessary.
I recommend putting some paper inside all the tubes and airways you expose, just to prevent from debris to get in.
Disconnect these tubes and orange sensor as well, also the cable harness with the zip tie. behind the upper intake there's a cable harness attached by a size 10 screw , use a small wrench to remove it (be patient, it's a small space and not much room to turn the wrench)
Disconnect all the tubes and sensors going the intake and also the brackets holding it.
the red stuff near my battery is rat poison, that didn't work against the rats ! the only thing it did was to change their poop color to red. however the many old school rat traps with peanut butter did the job (killed 2 huge rats)
Congratulations ! you have removed the upper intake successfully , only 1 more intake to go !
Start by disconnecting the sensor from the fuel rail and the 2 fuel tubes in the back (remove that plastic cube thats on them and release them by pressing the button) its recommended to put paper inside those fuel tubes to prevent leaks.
Unbolt the lower intake using the T40 torx socket, ignore the bolts with the dot in the middle.
have a friend moving that left cable harness to the side while you remove the lower intake, careful not to spill gasoline. before removing the lower intake it is recommended to clean the area and vacuum so no debris gets into the engine.
Welcome to the lower intake world
now things become sensitive, you'd want to put paper inside the holes leading to the intake valves and also block them with tape, vacuum around that area for any sand or debris.
Now the fun begins: so there's a coolant pipe that's blocking our way from reaching to the knock sensor, you have 2 options: 1. you can try if you can to work your way under the pipe and disconnect the sensor so you can work on it outside, to release the sensor, press underneath it and use your other hand or a flat screwdriver to push it outside. most likely that the mouse only ate the cables on the right side (bank 2) so you only need to remove this 1 sensor. option 2: this is a hard one but as you can see in this picture that's the route i took, removing the pipe !
how to remove the coolant pipe: first you will need to use a jigsaw very carefully in order to cut the welding between the 2 pipes. than you will need to remove the part where the coolant enters to this tube, i think there are 5 screws to remove there, 2 from the left side and 3 from the right side. also remove the small rubber tube on top. the tube is connected with a rubber o ring, once its loose just pull it with force. the further side of the tube is even harder to remove, first: it is held by 1 screw that goes under the tube (you might gonna need a magnet grabber or some grabbing tool to pick it up after releasing it) in my case pulling the tube was so hard that i had to tie a cable to it and pull it.
Once you've reached the sensor, identify the torn cables, remove the sensor and solder new and longer cables to it. than solder those cables to the 2 cables coming from the harness, do not mix positive and negative ey? the insulated tube where those cables are coming from has some exposed wires, don't get stressed this is a type of protection to the 2 cables we'd like to solder (i thought in the beginning that the mouse somehow destroid a 3rd cable but i called a few mechanic friends and they confirmed its just some insulation thing) once you've soldered the cables, insulate the SH^*T out of that whole harness and whatever you can protect from heat and rodents. spray the area with rodent repellent (car stores sell them)
Done? congratulations !!!
Now put back the pipe and use a metal cable tie around the 2 pipes to hold them together against engine vibrations. also connect back the pipe with the screw that was holding it in place.
Before assembly: use carburetor cleaner to clean the lower intake, vacuum it as well. if you managed to get a gasket, use it ! if not, use loctite silicone gasket maker. wait 20 minutes until silicone dries. do the same thing with the upper intake. if you use silicone you don't need to torque back the bolts, don't close them too tight. if you use a gasket do use a torque wrench and torque back the bolts.
Clean the upper intake and apply silicone
Finnish reassembling the engine ! you could also clean the throttle body with carb cleaner if you like.
feel free to consult with me if you're stuck at any stage of the job ! email@example.com