P0330 P0325 2004 5VZ-FE, or How I Learned to Stop Worrying and Love the Process

2004 Tacoma TRD, 4x4 MT With the 5VZ-FE. I'm at 265,000 miles when these codes came up. You know them, you love them, welcome back codes P0330 and P0325.

Did a bunch of testing and replacing but nothing worked. I'm going to write up what I've done so I can remember it better, and once I solve it hopefully someone can avoid the mistakes I've been making.

Here's the situation. Engine popped these 2 codes simultaneously a few months ago, I cleared the codes a few times but of course they came right back. After some light reading decided to replace the 2 knock sensors and the wiring harness.

FIRST ATTEMPT
I purchased new wiring harness and knock sensors;
Wiring HarnessORMAN 926771 (926-771) Knock Sensor Connector ($25ish)
Knock Sensors: Standard Motor Products #KS159 ($50 ea)

Tested the new SMP Sensors by putting the sensors in a vice and dropping a hammer an inch or so onto the vice similar to the way this guy did it in this video: [https://youtu.be/cKTcXESPOJM?t=197]
I got Mv signal back from each sensor, and they were both similar signals. I can't recall what they were but I want to say they were in the .1v range. Each sensor returned approximately the same result, my old knock sensors were NOT identical, so this indicated to me that my old KS's either were bad or at the very least not returning the correct signal. This is an assumption on my part.


(Image above is approximately the setup I used when testing the KS's)
I WONDER IF THIS DAMAGED THE SENSOR DOES ANYONE HAVE EXPERIENCE WITH THIS?

First install took a lot of time, about 6 hours all said and done. The wiring harness absolutely disintegrated in my hands when I took it out. Knock sensors both tested the same way and got different results, also it appeared that someone had tied the two knock sensors together in the wiring harness... I was not the first one to have gone here.

SECOND ATTEMPT
After installing both new knock sensors and new wiring harness, CEL came back on, same 2 codes. Frustrated, I dug back into it.
I found that I had crushed the knock sensor harness under the air intake manifold, and after thinking about it for about 20 seconds, decided to just replace the harness as it's cheap insurance. Got another of the same DORMAN 926771 (926-771) Knock Sensor Connector and installed it.

This time I also followed the wire back to the ECU using the pin-out info from this website:https://people.well.com/user/mosk/images/Early_Tacoma_ECUs_v2.pdf




Keeping in mind that the terminals are mirrored in the connector as the diagram is of the ECU pins, I did continuity from pins 22-23 to the 2 pins on the KS Pigtail connector ED1


(Image taken from http://www.markofshame.com/fsm/03_Tacoma/Repair_Manual/03tacoma/di/eg5vzfe/cip03250.pdf)

I got strong continuity between pin 23 and ED1 pin 1,
I got strong continuity between pin 22 and ED1 pin 2.
ECM Contacts were clean and free of corrosion,
ED1 pins were okayish, but not bad.

I got strong continuity on all appropriate pins in the new knock sensor harness as well.


After putting it all together, the code came back again. P0330 and P0325.
FML

ATTEMPT THE THIRD:
Current Situation, I suspect that the cheap knock sensors I put in ($50 ea) are not compatible with the Tacoma.
Part of the reason I suspect this, is that at idle the one knock sensor at ED1 was putting out .4mV, and the other was putting out 0mV... did I break them while I was bench testing them? are they just cheap? are they supposed to put out no voltage at idle and only works at higher RPM? no idea.

Before I dump $300 into new OEM sensors, I'm going to use my friends Oscilloscope and follow the troubleshooting steps in the FSM HERE, and see if it gets me any good news.I can at least verify if the waveform coming back to the ECU is correct or not.




So that's the situation, This horse has been beaten so dead it's all over the forums, I'm hoping that maybe the Oscilloscope can tell me for sure if the KS's I have installed are no good or not... lots of people on this forum have told tales of "ONLY BUY OEM" for the KS problem. Am I another to learn this lesson? probably. I'll update this when I get it finished.

 

Speaking of knock sensor replacements, one user in this post says "Not familiar with the knock sensor, sorry, but I have read where ppl mounted a GM knock sensor on the outside of the motor. Supposed to be better than the Toyota sensor (which doesn't prevent knock below 2k RPMs IIRC)."

Anyway, I'm not going to do that but i'll keep it in mind.
here's two different sensors made for toyota, Denso and MatsushitaI believe,

One user on this post over at "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."

^That mirrors my exact situation, experience, and frankly seems to show me I have to go buy Denso sensors.

 

Scoped the knock sensors.

At 4k rpm, bank1 was putting out 8.3kHz (not 7.1 Spec)
KS on bank 2 was putting out... actually nothing at all, just random noise.

Going to order new OEM Denso ones and try again.

 

Knock sensors ordered, going to try and put them in this weekend.
Also ordered new intake manifold gaskets as the ones I've got in there are twice used at this point.

 

I read somewhere on a auto repair forum where the author is having the same issue, it is a high mileage motor and he strongly suspects that what the knock sensors are sensing is a combination of all of the loose moving bits in the motor, happening at the right frequency and not necessarliy a pre-ignition event. He is testing his theory by moving the knock sensors farther away.

 

If the new, OEM Spec knock sensors don't work I'll look into that. I don't suppose you can find that thread lol.

I did see some people respond to this issue by re-locating the knock sensors, I don't know how I feel about that but it's certainly an option that will open up if this next solution fails.

 

This is what I did on my ratted out Pathfinder

https://www.youtube.com/watch?v=NHvt0IBJuBY

 

Update:

Spent all morning digging in, i can now get the air intake off and back on again in 4 hours. I'm getting good at this.

After replacing the cheap knock sensors with OEM Denso ones, the car works great. Let this be a warning to anyone who wants to cheap-out on the Tacoma 5VZ-FE Knock sensors, just do it right the first time, buy OEM even though it hurts.

Interesting note, the old, original ones that had gone bad were not oem sensors, and were identical to the cheap-out ones I had purchased.
I suspect that at some point this vehicle had the pigtail wiring harness go bad and the previous owner did exactly what I had done but with better luck, either way I've now put OEM denso sensors in, it works, no CEL, no codes.

 

Glad the OEM sensors worked out for you! Thanks for the documenting the trouble shooting steps you took and results.

 

This is a timely thread as I'm dealing with a P0330 CEL code. The amount of work is intimidating as I've never done any engine work.
Any thoughts on how long one could drive the vehicle without it being fixed. I drive the truck less than 300 miles/yr. It's one of those high mileage vehicles and had a new engine installed by a previous owner at 83,000 miles. The truck is at 272,000 now.