Code 52 Tech Thread
 

****THREAD EDITED BY OCDROPZONE TO ELIMINATE SOME BS THAT WHEN ON IN THIS THREAD, TRIED TO LEAVE THE TECH AS INTACT POSSIBLE***?'S-pm ME.***


It's fine to drive on it like that, you'll just get poor fuel mileage. When the ECU has code 52 registered, it enriches fuel mixture (not electronically, but is a byproduct of the retarded timing), and retards the timing. It's doing this in an effort to prevent detonation/pre-ignition.

Code 52 is just an electrical problem. It means that there's a fault in one of the following areas:

1) Knock sensor
2) The wiring (this is usually the case)
3) ECU (rarely the problem)

Always use an OEM TOYOTA knock sensor! Cheap aftermarkets have too many issues!

I had this problem with my rig...took me 2 yrs to figure out the fix... first thing i did was replace the pigtail... no go, next I tested the knock sensor, and idk if the test i did was accurate or not, but I did get readings as I would have suspected with a good sensor, so the next step for me was to rewire it directly to the ecu as some of the wiring was not real healthy... this also did nothing for me....still had code 52...
The next step I took was a bit more drastic, and I'm not 100% sure which was the fix, but I replaced the knock sensor, the valve cover gaskets and the pcv valve, and sure enough the code 52 went away, and the truck ran like new.... I knew I had a vacuum leak before which is why I did the valve cover gaskets, and I really suspect the vacuum leak was causing a lean condition and causing a knock which was out of range for the ecu to adjust timing, therefor throwing the code..... thats my best guess anyway. And for the record...I preformed the same test on the new knock sensor as the old, and got the readings I expected... the test was to hook up an multimeter to the snesor(were looking for milivolts here), run the vehicle, and see if the readings change with acceleration, as it should.

Good luck, and if you got anymore questions about it, shoot me a pm... I have a hard time explaining what I did in type...but I know this system pretty well now, and will do what I can.

The valve cover gaskets, and PCV had nothing to do with your fix. If you replaced those three items, it was your knock sensor.

The KS circuit is closed, meaning the only things that effect it are the ECU, wiring, or knock sensor. It's not a terribly difficult system to figure out.

In my experience, it's usually the wiring that fails.

I have to disagree.... I do understand that the ecu looks for a signal from the KS, and it is a fairly simple system. The KS senses knock, and then retards the timing to compensate, however, it only has so much room to compensate, and if there is still knock when it reaches its limit, u get the code 52. I always thought the same thing about the code 52...if u get it, there is a short in the wiring somewhere, but after all I have read, and all those I have talked to, I havent been able to come up with a definitive answer, so... my point is...if you are going in to change the KS, you will be right there and have everything needed apart to do the valve cover gaskets, and the pcv valve, so u might as well do them... I think the pcv valve was like $4, and the vc gaskets were about $20.... so kinda a no brainer.
I just wish I would have done that the first time I had it all apart.

Show me proof. You're wrong. When it reaches it's limit you ping/detonate/run lean. When the KS's are working they're damn near invisible.

I've been making and selling knock sensor rewire kits for MKIII Supras for years. I know how they work. Code 52 is just an electrical problem, having but a few problem areas.

Where in the list of trouble areas does it state anything you've said?
http://i29.photobucket.com/albums/c2...h_30ef938a.jpg

While I agree with you on the preventative "while you're in there" maintenance, you're just flat out wrong in your other statements regarding the causes of code 52.

well, thats why I said I'm not 100% sure..... but unless someone shows me proof that it isnt possible....

*edit*

Ok, just re-read my post... guess I never actually said I'm not 100%, so my bad.

To the o.p..... if your changing the KS, change the vc gaskets, and pcv valve while in there..if you have the time and $, I would also send the injectors out to be cleaned, and replace the t-belt, and water pump as well....

if i were you before you get TOO into it like i did with mine, check the sensor itself. make sure its not loose like mine was. code 52 was plagueing me, i ran a new wire from the ECU to the plug, no change. changed the plug, no change. finally, at my wits end, i go to remove it to replace it. what do ya know.. it unthreads twice then falls off in my hand. i tighten it up good, plug it in, and never came back on. so something to look into...

I'm telling you dude, that's not how the ECU works. I fully agree that you should do the other stuff as preventative maintenance, but none of that will effect the knock circuit. Another +1 for injector cleaning. I sent mine to RCEngineering and the truck never idled/revved better! Good advice. :)


Yes.
Your wording is throwing me off, but I'll bite. On the MKIII Supra, (remember, the turbo model engine bays get VERY hot) the OEM wires just get old and brittle. They fail, thus causing code 52.

The rewire kits I make for them are almost plug'n'play, use brand new OEM connctors, coax wire, and 99% of the time fix the problem. The only time one of my harnesses did NOT fix the problem was when someone had one or both knock sensors that were faulty.

Code 52 is a common problem with the MKIII Supra, but is very easy to fix.

One thing to note.

The torque spec on the knock sensor is only 52 in-lbs. I had to do a bunch of digging to get that from a master-tech at my local dealer, as that is not in my '89 FSM. If you overtorque the sensor it shears off internally below the nut feature and can cause an internal issue with the sensor.

Just one more thing to throw out there.

I would start with the wiring from the pigtail to the ECU, as you are doing now. That wiring harness gets really stiff over time and you may have cracked a wire moving it around the engine compartment during the rebuild.

Good luck

I would put old brittle wires at the top of my list of things to check. Figure the wires are at least 16yrs old or so, which leaves a lot of time for things to bake in the engine bay. The most common problem is the wiring. The knock sensors don't usually fail, but it does happen. Many times from people hitting them with a wrench or something along those lines.

You're very welcome!
This is actually what I ducked back in here to cover. I didn't remember the exact torque spec (thanks for posting it!) but over torquing them will result in false readings as well. The knock sensor(s) listen for a very specific hz frequency at which knock occurs. I'm unsure of what that exact frequency is on the 22re/3vz, but on the MKIII Supra its around 7hz. That's the point at which the ECU will start to retard timing, and enrich the fuel mixture in an effort to prevent detonation/pre-ignition.

I have also seen the KS's break due to people over torquing them. (not on the 22re's but other motors.
Right there with you. On many cars there's no way to reach some areas with a torque wrench, so you've gotta develop a feel for about what's right, all the while keeping in mind how heat/cold will effect that area of the motor.

I definitely agree with that as well. The biggest job I've had to do with my 22re is the headgasket at 140k. I blame it on the PO's lack of maintenance. It's got 170k on it now and runs like a top, burns no oil. I can't kill this thing!

So do you still make the kits? Would they work on our trucks? From what I understand the pigtail that one would buy from the dealership has to be spliced in. I would love it if I could find a plug and play kit.

I do, but only for MKIII Supras. I've only worked on a few 3vz powered trucks, so I don't know how long a wire to use, or even what connector they use.

As for the 22re, I would have to find out if the connector is available from Toyota or not.

Right, because it's usually the wiring that goes bad, as I've mentioned numerous times in this thread. And if it's not that, it's the sensor. The ECU usually doesn't go bad...

And I mentioned that there's a specific frequency that the KS listens for. Each motor has a specific frequency at which spark knock/detionation/pre-ignition occurs. So what new information can you add?

Yeah, don't do that. What a cob-job, not to mention that then your motor has ZERO protection against spark knock...


No, it IS an electrical problem. I don't THINK it. I KNOW it. Read the FSM, and read up on how knock sensors work before you jump to conclusions. It has nothing to do with vacuum.

edited

No it's totally cool, if you prove me wrong I'll kindly admit that I'm wrong. But I still seriously doubt that I am. LOL.

You are straight wrong about that though, your motor can knock all it wants, and you won't get code 52. That's why I'm getting my panties all in a wad. Code 52 does NOT mean that there's a problem with ignition, or any khz frequency, it means that there's a problem in the knock circuit.

Find me a definitive source that states that if your khz readings are outside the specified range that you will get a code 52.

When the knock sensors operate, they do so invisibly. When they're working, or when you get ping/knock/detonation ,there is NO code for that! It's like I'm beating my head against a wall...

Edit: and yes, it's crucial to have that shielded wire grounded well. ;)

Sure. However, what kind of noise are we talking about here? Electrical noise, or mechanical noise from the motor?

Ok I agree that just the signal is closed. By "closed circuit" I simply mean that the knock circuit is not tied to any other circuit's function aside from the ground.

I understand that the FSM isn't the be all/end all of vehicle repair. However, if you're implying that mechanical noise is causing the code 52, then I disagree. If you're implying that outside electrical noise is penetrating the coax, then yes, I agree 100%, which brings us right back to the wiring being the issue.

I think outside the box on a daily basis, but sometimes thinking outside the box isn't necessary to solve a problem.

the KS circuit is a dedicated circuit. one wire to the KS and no wire returning. the wire returning completes the signal to the ECU when the KS closes (senses pre-detonation) and shorts to the block. The ECU senses the new load on that particular output, in this case the KNK pinout. Attachment 186907

So I will withstand a correcting, there is only ONE wire going TO the KS and none returning. That much further solidifying the point of shaeff and myself. You have a short, bad KS, or a frozen contact/short in your ECU. Or your timing is advanced too much and causing a knock.

We agree on all but this one point. :)

Regardless of whether the motor has spark knock, rod knock, or something loose banging around, none of that will cause code 52.

I already sent him a PM asking if he could shoot the info my way. And in all honesty, I can't explain why moving the sensor worked. Makes no sense.




They do NOT disagree with me. I never said that an outside noise couldn't cause the timing to be retarded if, under the rare circumstance, that noise was at about 7hz. Your excerpt quoted above says NOTHING about illumination of the CEL due to said outside noise interference. ;)

This does not mean illuminate the CEL and register code 52. It means that it would output the signal to the ECU to call for retarded timing. (which is a max of 10* of retard by the way)

Evidence would be lack of power, acceleration, rich running condition. NOT a CEL. ;)



Edit: and this is exactly what I've been saying the entire time, which actually helps me prove MY point:
:)


Edit2: and here is a quote from my friend, all of which came from the TCCS (Toyota Computer Control System) manual:

Move the knock sensor back to the proper location and report back. I'm willing to bet that you got a bum sensor from NAPA.

I'm no electrical genious. I will be the first to admit it. I DO, however, understand how the knock circuit works, and what will and won't cause code 52. Even a different bend in the wire (if it has a potential bad spot in it) will stop the code from popping up, until it shorts again.

Here are pages directly from the Toyota.


And as for this: it will not work. Think about it- if shorting the ground to the signal wire causes code 52, then so will putting a resistor between the signal and ground wire. All a resistor does is reduce the voltage flow between the two terminals. Even still, you're still shorting signal to ground, which would cause code 52...