Knock Sensor Failure Likelihood 3.4L with 70,000 miles.

I'm trying to determine the likelihood of a KS failure on the 3.4L with 70,000 miles. I see new OEM sensors are ~$161 each. So we're talking $320 to replace both as preventative maintenance. I noticed Intermotor (repackaged Denso) at Rock sells for ~$122.

If these are truly high maintenance items, I guess I will replace them. Though, past experience with other Denso managed vehicles hasn't surfaced a problem in over 200,000 miles.

Other question, do 3.4L Tacomas throw an OBDII "ghost code" for a KS, that accompanies other codes like Evap or O2 sensors. A couple of my vehicles throw KS "ghost codes" along with O2 sensor or Evap system codes. Fix the O2 or Evap problem, and the KS code will disappear like a ghost.

 

Unlikely they went out that low of miles. But it's possible. I very rarely hear about a knock sensor problem. I know the short harness that plugs into them can cause problems.

 

On one of my cars, it's a PITA two-day job to pull the intake plenum, injector runners, and water piping to go into death valley to replace the knock sensors. The knock sensors rarely fail but the wiring harnesses attract varmints that eat the wiring insulation. So more KS problems come from chewed up KS harness wires than the failure of the actual sensors.

The one in this picture was hanging by a thread after being chewed up by a rodent. It found it in a car that I had just purchased.



I triple insulated the new KS wiring to avoid the problem in the future.



Honda's solution is to offer a rodent repellant tape. I have not heard any good reviews about this tape to warrant using it.

I'm not kidding about the Honda rodent tape.



Past experience with knock sensors that are buried at the bottom of death valley.

 

i had a rodent up in my air filter housing once chewing through the filter
truck stalled on me on the freeway interchange overpass
no idea how the buggard climbed up in there from underneath

 

I’ve had 1 taco come into the dealer with knock sensor codes because off coolant in the valley causing some kind of electrical gremlin with them...

Your not loosing coolant right?

 

Well, my experience is precisely one vehicle (142K miles), but I'll say LOW. If you're having the intake off (as I did to fix a water bypass pipe leak), then I'd say the short harness piece associated with the knock sensor should be replaced. (This step was recommended to me beforehand, and sure it enough, it disintegrated when touched; but it's inexpensive.)

 

I had one go out around 75,000 miles (2nd gen), no chewed wires I could find all connections seem solid so. Replaced both sensors and whole upper wire harness since i was in there. I did have a coolant leak from the throttle body bypass hose prior to that so coolant may have gotten into the sensor or wiring.

I am supercharged so maybe that helped prematurely kill the knock sensor

 

Listen to this, I accidentally knocked one off of a work table in the garage. I saw it bounce when it hit the garage floor. I picked it up and put it back on the table and later used it without thinking about it breaking. It was bad. So I learned the hard way, not to drop a KS.

I've seen a number of knock sensors destroyed by unsuspecting owners who pressure wash their engines at car washes. They fill up the valley with water and it drowns and ruins the KS.

I know that on engines that are designed to run premium fuel if you don't run it then it shortens the KS life. That's a common issue on Nissan engines that require premium and the owners insist on running regular fuel. Get ready for premature KS problems.

 

Typically they don’t fail at that many miles,

I bought mine off eBay for 85.00 for the set.

There are fake aftermarket ones out there.

Original DENSO have the following

Mine were stamped DENSO and had a DATE stamped on them and each was sealed in a bag with part number

Those 3 things check list items will show it’s an original DENSO knock sensor.

 

No coolant loss. I'm just prepping a 70,000 replacement engine for installation and want to take care of hard to reach items while the engine is out of the vehicle.

 

Thanks for the tip. I'm seeing prices that I'm familiar with now. I picked up the set of knock sensors in this picture for $22.90 on eBay.



I'm looking for a deal on Toyota OEM KS wiring harness.

 

Cool, ask the seller if there is a date code which should be less than a year old and that it’s stamped DENSO and your good, if not don’t take a chance on them.
Knock sensors are a critical part of your motor on how it will run and a good 4 hour
job to replace if they don’t work Correctly

 

Thank you. Question sent.

Side question since I have a good running Taco to use a test mule, is there a way to test the new Knock Sensors with that vehicle before I install them in the valley on the replacement engine?

On two of my other cars, I can install a new KS with a new wiring harness in an alternate (easy to reach) location like the picture to test it before going under the valley.

If I could do this, I could rule out any KS issue before going in deep.

 

I think the only way to a test a knock sensor is under load and at high rpms for a new one assuming it good. A used one can be checked with a meter

 

Interestingly, I just found this post about varmints eating Taco KS wiring. So I will take steps to super insulate the harness, as I did on the other back in 2010.

 

I think I see the spot most likely to be attacked by a rodent in this picture below. Right in the Y where the harness splits to the two sensors.

I wonder if the Knock Sensors use British Standard Pipe Thread pitch like an oil pressure sender switch?

 

That engine valley and block deck look puuurty. Did you have the deck machined? (Surface the head bolts to)

 

It's not mine. Just a random block pic to show the KS location. I do get into working and cleaning up over whatever engine project that I have going at the time.

Here are a couple of my projects for aluminum engines that I have torn down and refreshed.

VH45DE - approaching 10 years ago.



For when you need 270 ft lb of crank pulley bolt torque.





VQ30DE - approaching 6 years ago.



5VZ-FE - Starting a new mid-life refresh project in May of 2019.

 

Ah. Sensors usually good. Replace the harness though

 

If I didn't already mention, since the engine is out replace the transmission front seal and the T case seal that connects to the transmission if you can

Also the heater core upper hoses might do them too as the rubber is getting old now.
Again so easy to do it now