Knock Sensors Plus

Hey Everyone,

I'm reaching out regarding my 2005 Toyota Tundra double cab, with a 4.7 L engine and an automatic transmission.

I just had my center carrier bearing and U joints replaced, and when I picked up the truck the check engine light was on. I used my small code reader at home and it told me the knock sensor number two was out.

The O/D switch also seems not to function, post driveshaft work. The light comes on when I hit the button but no change in RPM.

I also took a look underneath the hood and saw what I believe is rat droppings, something that wasn't there before hand. So now I'm wondering if the wire harness has been chewed, would that cause a bad sensor reading?

To replace the sensors, I've read where some have taken off the entire intake manifold and others are removing the fuel rails to access the sensors.
Which one makes more sense?

Also, as will happen with a truck that has 243,000 miles on it, I have some oil leaks.

I don't have access to a garage or a place where I can do the work myself, and honestly it's been so long I wouldn't trust myself to do the work.

Am I making a dramatic leap by suggesting instead of getting the knock sensors and leaking gaskets replaced, it might make more sense financially to buy a remanufactured 4.7 L engine?

I really like the truck so getting rid of it is not on my radar. I just need to know the smartest way to move forward as far as the knock sensor in the immediate future, and the leaking gaskets down the road.

I feel I don't need to ask, but I probably want to stick with OEM parts for the sensors, correct?

Thanks, and hope you're having a really good day!

 

A new engine is a big leap for sure. It’s likely a wire harness has been chewed and can be repaired on the cheap by someone with the knowledge. If you’re gonna replace anything, OEM is always a good choice.

 

I appreciate the insight. If it's a wire harness, it still means the intake manifold has to come off. I have an uncle who has a garage and shop in his backyard and I can enlist his help.

A new engine is a huge leap and pretty damn expensive by any measure.

How do I keep rodents or anything else from crawling back up there? I read where somebody applied rodent repellent to the gaskets but I sure as heck don't know how that would work especially with the heat of the engine itself.

Thanks again.

 

Are you positive the wire harness is damaged under the intake? The knock sensors are located there, but the wires could be damaged anywhere along the harness.

 

I am honestly not sure at all.
I know there wasn't an issue before the driveshaft work and now there is. Probably a coincidence, but I'm not sure where to check although it was recommended I check the ECU to make sure all the wire harnesses are properly plugged in and all the connections fit.

That I can do.
I'll keep you posted.

 

Correct me if I’m wrong but this appears to be somewhat of a rehash concerning your thread from 2 weeks ago regarding O/D and Knock Sensor ??

If so, checking ECU was mentioned back then since you had changed your ECU.

https://www.tundras.com/threads/o-d-button-on-a-2005-tundra.122963

 

You're correct, and I knew I posted that but I couldn't figure out where. Thanks for catching it. I'm going out to check my ECU today. I'll take a look at the wiring harnesses that plug into it as well and try to chase as much of that behind the firewall as I can. I don't mean to clutter these boards with more than one query and post.

 

No problem, pointed it out not only for you but anyone that come along attempting to assist in this thread.

You also did a thread in the Build section that you might want to consider linking a followup in that thread either pointed to this thread or the original thread linked to above with same issue.

https://www.tundras.com/threads/2005-o-d-button-issue.122909/

 

I need to figure out how to do that but I will.

This may be a really really dumb question, but if the problem is the wiring harness is it possible the knock sensor is not bad and that the code is being thrown because of the harness itself?
(I can teach you how to handle a sword, jump off a building, and put a car up on two wheels but I am a little short of knowledge when it comes to this stuff).

I thank you for all of your help.

 

Yes, if the ECU can't read the sensor, or the sensor is shorting because it's chewed or grounding, who knows what the ECU will interpret.

As for how to avoid rodents under there, good luck. Maybe you could rig up some mesh or something at the gap in the front when the intake manifold is off?

Reference reading: https://www.tundras.com/threads/if-you-get-a-p0325-code-or-a-broken-wire-on-a-knock-sensor.52632/

Note though: This isnt' hard work, there's just lots of connectors to pop off, and you'll need to replace the lower intake gasket, which ... buy OEM on that, learn from @bmf4069's mistake. You just need the lower gasket, not the one that goes between the clamshell halves of the intake manifold.

I take it you've been through a full tank of gas already, to ensure it wasn't gas causing a knock? (The rodent droppings are suspicious af though)

 

It's really not bad to pull your intake off, and I'd almost guarantee rats chewed your harness.






I used the ITM gasket from RA like shifty said. Don't do that.

 

Get a couple bars of Irish Spring soap, cut them into quarters, drill a hole through them and hang them with zip ties around your engine bay. Works for me but I’ve also had customers come in with those noise makers/flashers.

 

@shifty` - I've been through a tank of gas with Seafoam and nothing has changed. I disconnected the ECM and checked all the pins as well as checking the wires to each of the five plugs as best as I could. Connected everything back up and started the truck.

The check engine light was not on... Until it was.
As well engineered as this Engine is, I am surprised some thing like this was missed, this little gap at the front. I know rodents can squeeze into teeny tiny spaces, but I can't find for the life of me how they got through. Doesn't matter what I think, since clearly better and braver have traveled this path before me.
I love the idea of the mesh, and think I will do it. I'm beginning to believe I'll be taking this on myself (although my uncle said if he can clear the yard and shop, I can bring the truck up).

I can't find anything wrong with the wiring harness anywhere that I can visibly trace it.
Thank you also for sharing the Wayback Machine article.

@BubbaW - I think I took care of all of my wandering links, posts scattered as if banished from the tower of Babel. Thank you for posting the PDF version of the link with the images. This instructional is clearly a labor of love. I appreciate the individual who invested the time and effort for the rest of us.

Because I currently work remotely, I'm not terribly concerned about my vehicle so much as I'm concerned about the fact I live in an HOA deed restricted community where people can be real pains in the butts.

@bmf4069 - thanks for the photos. Really, all in all, I feel I can tackle this and I'm beginning to wonder if I should just order all the parts I need even the ones I don't think I need. Like the fuel injector O-rings? I feel like if there's a way that things can go wrong, they will.
As for parts, like the gaskets? Definitely going OEM or better.


Just an FYI - performance sucks. It's behaving like it's bogging down. I'm getting 9-10mpg currently (down from 17.5-18).

 

That's about the mpg I was getting. The knock sensor harness Toyota sold me didn't work, so I had to splice it in. Yours should be good. Just make sure you have a 22mm wrench for the fuel rail, and make sure you put the washers back in order on the fuel rail connection.

This was my first post on the forum. It may not help, but it's my backstory.

 

Welcome to my world

I have a mix of driving and was getting mid-11s and sometimes 12s for mpg, then I cleaned my MAF and did a few other small things, and managed to get that up about +1 and sometimes 1.5mpg. I'm lucky to pull 13mpg mixed driving and haven't been able to hit 17 for the entire 5 years I've owned the truck, not even on a straight-hwy trip consistently 70-80mph.

 

@bmf4069 - Backstory or not, I. think all information helps, and as far as backstories goes, yours is the Tundra forum equivalant of Ivanhoe: a good read and filled with details.

 

@shifty` Yuck on your MPG. I went to Toyota from Dodge because I had a Dodge Ram that after a flash update went from 50 miles a gallon to 9.
I don't hypermile, but I've had the truck since it had 3 miles on the odo, and it has always given me 17-18.5, except when I'd drive like I think I am an extra on Fast and Furious, which I don't do anymore.

 

With a knock sensor issue, the ECU should be going into Fail-Safe(Limp Mode) but let it run at a minimum speed....limp home. It's telling the fuel system to go rich and retard the timing, causing fuel economy to drop.
With those conditions, it could be the reason why you are not seeing a reaction when you select OD OFF

Those are dang good numbers when it's actually running good. My last fill-up was 17, mostly highway miles, few short trips and a few Italian Tune-ups along the way. We also have 100's of log trucks going to paper plant each and every day, so going around them like a bat out of hell occurs often.

From one of your previous threads.....

I have to tell ya I am still stuck on this ECU exchange you made and the reasoning behind it.
Do you recall what code it was giving concerning ECU and could it have been the knock sensor code ?

Would be curious to see how the old ECU reacts once you get all codes cleared.

 

Hey @BubbaW -
I don't recall the code for the ECU but I do specifically remember when I did the research it said the code was the ECU.
I didn't even know I had a computer in the truck although I had an idea. I certainly didn't know it was going to be so easy to access and replace. Once I did replace it, and ran the flash drive updates into it, performance returned to previous standards.
I only ever got the one code which was for the ECU.

The knock sensor code is a different code and I started getting that after I picked my truck up from the drive shaft work.
Dingbat that I am, I may have tossed the old one (ECU) although I'm pretty sure I still have it.

 

2WD vs 4WD is a lot of it, I think I'd be averaging more like 14 with my mixed driving if I was 2WD. I came really damn close to hitting 17, but only driving in AL through sections of the interstate under construction where it's long stretches of holding 55-65mph and the clock is sitting around 2k RPM consistently. that was basically after I started logging my mpg using a smartphone app 6-12 months into ownership, and I've only come close to it 3-4 times since. (truck had around 64k-ish miles when I got it)

​

 

It's sad, because I get pretty whiny sometimes about only getting 17 18 1/2 miles to the gallon when my wife's Nissan Rogue, when I drive, it gets 35 miles to the gallon (she gets 5mpg less).
Still, my mileage is better than what I was getting in my stupid Dodge Ram.

I'm not complaining now that I'm only getting between 9 and 11 miles to the gallon until I get this darn thing fixed.

 

Decided to go out and look under the hood because I wanted to see for myself exactly how a rodent would get in there. Sure enough I see a space big enough(under the 4.7L of the intake) for a party to walk through. Pretty sure I also saw chewed up wires where they would connect to the sensor plug, since I saw no wires coming off the plug attached to the sensor itself.
I tried to get photos of what I saw but nothing doing. I suppose it's a safe bet that if one knock sensor connector wires have been chewed off, the other one has as well?

I'm convinced this happened at the shop where they did the work on my truck. There's no way to prove it though. dang it.
Anyway...How do I fix this (the best way to do so): replace the ENTIRE harness? Splice wire in place?

Is there an intersection between economy and durability?

 

You’ll have better idea once you remove the intake if the Uncle thing works out. At that time you can post more conclusive pics for others to then offer advice on best splicing suggestions.

I do like the lack of rust on nuts/bolts from what we can see

 

@Bubba - I'd like to think I've done a pretty good job of taking care of my truck.

I'm not exactly sure I'll be able to splice if the rodent chewed all the way to where the wires go into the plug, which wasn't very thoughtful of the critter. If what I saw was correct, I may not have an option except to replace the harnesses.
But you're right and then I'll have a better idea once the intake manifold is off.

If I can get the truck to my uncle, he's pretty good and creative, since he builds rat rods so he knows a thing or two for sure.

 

Leaning towards replacing the harnesses. Best source for OEM or equivalent?

 

Best source for OEM is Toyota Parts, and there is no equivalent on wiring harnesses, I wouldn't use anything aftermarket unless I knew the person making it

But like @BubbaW already told you, and @bmf4069 would probably warn you, you probably need to get a peek under the manifold, see what you're up against. You don't even want to see how much new knock sensors cost, but if the little rat bastards damaged the sensor itself, guess what? If you know anyone with a borescope or similar snake-camera for plumbing etc. you should be able to look around and confirm presence of rodent activity and maybe see the damage you're up against.

The thread I linked above, the OP there said he just needed to re-terminate the connector, and p/n 82219-35010 was a compatible part, though it was for a '95 Toyota.

 

Yeah, the knock sensor itself doesn't have wires, so they can't chew them. You'll just need a new harness. Pulling the manifold only takes me about 45 minutes nowadays. Probably 90 minutes the first time.

 

I think that's probably a stealership only part.

 

You say that, but if this were me, knowing my luck, those little bastards would've chewed on the physical stump of the sensor

 

I called the dealership and they gave me part number 82998–12790. It's a terminal repair wire. It's a single wire, and since I need two for each one of these sensors I need four total, and the price for one is $18.96.
It looks like a piece of wire and nothing special. I feel like I'm missing something.

The girl I just talked to in the parts department says it doesn't come as a connector and wiring harness- they are two separate pieces...