Knock sensor failure vs actual engine knock

[K-Tanz]

I have a 1997 3.4 auto and I had my engine completely resealed last month. While he was in there the tech pointed out that the knock sensors were original (and old, 220,000 miles) and suggested I replace the harness and sensors while the engine was apart because it's such a pain in the ass to do it again, and while you're in there you may as well. So I said sure. I bought some advance auto knock sensors and a toyota factory harness for him to install. All seemed pretty well for a few thousand miles, drove it from AZ to Colorado, I've been up and down the Colorado mountain passes with no issues.

Well the other day I overheated. This is unrelated except to say that while I was waiting for a tow I was bored and pulled codes. Lo and behold P0330 knock sensor 2 bank 2 circuit malfunction. This pisses me off for many reasons, but I have a shrink for that.

My question is if this is definitely a hardware failure of the sensor or harness, or if the engine could indeed be knocking somehow. I called a local shop and he said he'd put new sensors in for $400 in labor. Seems totally fair. I want to buy Toyota original sensors and bring them to him to install, but I don't want to buy the sensors and then have him figure out "oh dude your engine IS actually knocking and that's not a faulty sensor".

Engine seems to be running fine. Seems to maybe be down on power on the mountain passes but it's my understanding that is what a knock code will do, kill your power to try and save the engine.? But it's running smooth (other than overheating which I'm fairly certain is unrelated and had to do with a disintegrated radiator cap). Running nice and smooth. No knocking, no weird noises other than some belt squeal.

Is there any good way to tell the difference, or would an actual problem that sensor is catching be pretty obvious?

Basically I don't want to buy $400 worth of knock sensors from Toyota and then not need them. I am sure any dealership is going to hassle me about returning sensors or electronic equipment and I don't want to waste the money on two sensors that I don't need.

Thanks for reading!

 

[phattyduck]

The knock sensors are completely ignored below ~3k RPM (which is why the supercharged guys have so much problem with low RPM ping...).

Sounds like the problem here is that you replaced reliable OEM parts with aftermarket crap... You can do a bit of diagnosis on the sensors to see if they are shorted or the resistance is out of range first. The code is not that you are getting 'too much knock' - it is that there is likely a problem with the sensor.

-Charlie

 

[K-Tanz]

Yeah lesson learned. I rolled the dice on shit that was half the price and it will bite you in the ass every time. Hindsight and such. I'm guessing the sensor is the issue, I just want to be sure it's a sensor issue and not an actual engine issue before I drop the cash for the real deal toyota sensors.

 

[Devbot]

As someone who had to do their knock sensors maybe 4 or 5 times while chasing a gremlin, you must use OEM sensors from Denso. Toyota used Matsushita originally and eventually moved to Denso as they're more reliable with cleaner signals and I can attest to that. I eventually learned the ECU is very sensitive to the waveform they put out and it needs to be damn near perfect - even if it's in the general shape and fairly close frequency it can still throw a code.
It should also be said to be careful not to pinch the harness, and there is VERY little space for it to come out from the valley (almost nonexistent, really) and if it gets pinched and torqued down you'll be right back at square one.
I think the very first thread I created was on my knock sensor gremlin and you may or may not find useful info within it. You should be able to find it scrolling through my profile - I'm on my phone and don't have the link right now. It is a giant pain but ultimately I would recommend you chase this as much as possible yourself, or you're gonna be paying an arm and a leg just for them to do so.
You CAN test them on the vehicle without disassembling the engine but it'll only get you so far. If you want to test the sensors individually on an oscilloscope or test continuity through the harness you have to tear down the engine to do so, and tear down quite a bit at that. The entire intake assembly and fuel rails have to come off. However in my experience, if it was an electrical fault the CEL would come on pretty quickly (almost randomly) and will always return no matter how many times it cleared.

 

[19963.4lsr5]

It still annoys me Toyota doesn’t check for knock/detonation till 3000k and above.


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