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CODE 52, Knock sensor gurus please read.

Old 09-18-2015, 03:25 PM
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CODE 52, Knock sensor gurus please read.

First off Im not drunk LOL, 2nd .. I am no stranger to Code 52.

Ive fixed many knock sensor issues, on many 3.0 V6's over the past 15 years as a mechanic, but Ive run into the ultimate code 52.

1989 4runner, 1st Gen body style, 3.0 V6 Automatic 4x4
Just rebuilt the Top end of the V6, replaced the knock sensor wire while I had the heads off, (I always do ). Fired up the Truck, sounds good, runs good.
No check engine light.
Going through all my checks before I take it to smog (California BS) and I noticed my Timing was like 22' btdc, and realized my TPS was bad. I pulled off the throttle body to remove the TPS easier cause the bolt heads were stripped. Swapped the TPS, bolted the Throttle body back up, fired it up, set timing to 10' BTDC with in Diagnostic mode. Went to drive it, CHECK ENGINE LIGHT comes on...code 52

Years of this I know Code 52 is caused by only 3 things.
1)Knock sensor 9% probability
2)wiring 90% probability
3)computer 1% Probabiltiy

I figured I must of bent or moved the knock sensor plug working on the throttle body,(as 90% of Code 52 is the old frailed wiring) unplugged the KS connecter, straightened it. Reattached it. Still code 52.

I have a knock sensor I saved, that I know is good, for my testing, its drilled and tapped to the Engine lift hanger, with a new tail plug on it, I bolted it up, unplugged the main KS connector, and connected it up the by pass.....Still code 52

So I figured my wiring is bad. So I got a co axle wire (tv cables work great)
I ran a new wire, from the main KS wire connector, under the throttle body, to the pin location on the Computer. I cut the wire , connected the new co axle wire, grounded the shielding cover wire, only on this end, to the computer ground, where the computer bolts up. Fired it up...STILL CODE 52!!

I then pulled the wire from the main connector, hooked it up to my by pass knock sensor....STILL CODE 52...

Before I swap computers is there anything I missing??? Its been a while since I ran a whole new wire, I only ground it at the computer end right?? Code 52 is a sumbitch.

Last edited by some drunk guy; 09-18-2015 at 03:27 PM.
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Old 09-18-2015, 05:27 PM
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Dang, SDG, you do know a lot about knock sensors.

All I can add is that user AZSpeed claims that he got rid of his Code 52 only by replacing all the capacitors in his ECU (you may be able to find his post using his username). Obviously, not ALL of the capacitors affect the knock sensor, but I sure don't know which one does.

There are certainly those who disagree, but I don't believe mounting a knock sensor to the lifting hook would do any good at all. If it did, why would Toyota bother to "hide" it? But it sounds like you've tested all around that too.

Good luck, and let us know what you find.
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Old 09-19-2015, 04:11 AM
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how is the pin in the ecu plug? i use spare new pins to test connector pin wear in plugs, but you can substitute with something of same size, often paperclip or pin. how are the grounds? engine to body, engine to battery, battery to body, ecu to body. how's the voltage going to the sensor? how is it plugged in? should be fairly constant like 5v steady and 2.5v plugged in.
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Old 09-19-2015, 08:18 AM
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As I read your post, SDG, I don't think you're done testing things thoroughly. You've made a great start, and done exactly what I would have done up to this point. You've done the relatively easy stuff first, which is a great approach. Here's where I see you are right now.
- Replaced the wiring from ECU to plug. Check
- Tested with a known good sensor in a questionable location. (engine hanger - jury is still out on whether this location works reliably). Failure is inconclusive.
- Tested with an unknown (original) sensor and pigtail in a known good location. Failure is also inclusive.

Unless I missed something, you haven't tested a known good sensor with a known good pigtail in a known good location. Unfortunately going further means removing the plenum, but that might be in your future.

It might be easier to first follow up on the capacitor idea if you're comfortable with a soldering iron (sounds like you might be). I think that's what I would pursue next. I'd much rather do some soldering than pull the plenum.
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Old 09-19-2015, 09:15 AM
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Leave a ground wire loose? If not, might want to sand the ground contact points.
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Old 09-20-2015, 08:22 PM
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Update: fixed!

So after reading many many posts, people kept mentioning The Tps sensor and distributor could be culprits in causing " noise" that may interfer with factory signal. Hard for me to believe as its kinda seperate signals to ecm but...

So today I did 2 things, what exactly fixed it I don't know... For sure, but I re set my new TPS, as it was slightly out of adjustment, I also eliminated my new tail plug I had put on my knock sensor on the engine hanger, and I connected my new co axle cable end directly onto my known good knock sensor ( on the engine lift hanger)

No more code 52!!

And just to clarify..

Code 52 is Not caused by an engine that make have a loud knock, the check engine light comes on only when the computer does not read a signal from the sensor
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Old 03-03-2019, 10:14 AM
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Code 52 knock sensor 89 4Runner 3.0 V6

Originally Posted by some drunk guy View Post
First off Im not drunk LOL, 2nd .. I am no stranger to Code 52.

Ive fixed many knock sensor issues, on many 3.0 V6's over the past 15 years as a mechanic, but Ive run into the ultimate code 52.

1989 4runner, 1st Gen body style, 3.0 V6 Automatic 4x4
Just rebuilt the Top end of the V6, replaced the knock sensor wire while I had the heads off, (I always do ). Fired up the Truck, sounds good, runs good.
No check engine light.
Going through all my checks before I take it to smog (California BS) and I noticed my Timing was like 22' btdc, and realized my TPS was bad. I pulled off the throttle body to remove the TPS easier cause the bolt heads were stripped. Swapped the TPS, bolted the Throttle body back up, fired it up, set timing to 10' BTDC with in Diagnostic mode. Went to drive it, CHECK ENGINE LIGHT comes on...code 52

Years of this I know Code 52 is caused by only 3 things.
1)Knock sensor 9% probability
2)wiring 90% probability
3)computer 1% Probabiltiy

I figured I must of bent or moved the knock sensor plug working on the throttle body,(as 90% of Code 52 is the old frailed wiring) unplugged the KS connecter, straightened it. Reattached it. Still code 52.

I have a knock sensor I saved, that I know is good, for my testing, its drilled and tapped to the Engine lift hanger, with a new tail plug on it, I bolted it up, unplugged the main KS connector, and connected it up the by pass.....Still code 52

So I figured my wiring is bad. So I got a co axle wire (tv cables work great)
I ran a new wire, from the main KS wire connector, under the throttle body, to the pin location on the Computer. I cut the wire , connected the new co axle wire, grounded the shielding cover wire, only on this end, to the computer ground, where the computer bolts up. Fired it up...STILL CODE 52!!

I then pulled the wire from the main connector, hooked it up to my by pass knock sensor....STILL CODE 52...

Before I swap computers is there anything I missing??? Its been a while since I ran a whole new wire, I only ground it at the computer end right?? Code 52 is a sumbitch.

Replaced motor with rebuilt engine after head gasket issue. Started engine got up to 1600rpm cel come on with code 52 knock sensor. Took it to a technician found out #4 injector issue. Tech moved the wire around and reconnected the connection to the injector and in doing that wiggled the short harness for the knock sensor and the cel went off. Bought all new injectors, knock sensor, and short harness. And now the code 52 is back. Took it back to the tech and checked and verified signal to the ECM. Not sure where to go from here. I’ve purchased a used ECM and just waiting to check and see if it fixes the issue. Any advice would be great.
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Old 03-03-2019, 11:32 AM
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Originally Posted by JoshThompson View Post
... in doing that wiggled the short harness for the knock sensor and the cel went off. ...
What does that tell you? That wire (often called the knock sensor "pigtail') is in a hellish environment and often goes bad. The knock signal is a very low level signal, and crappy shielding or insulation will keep the ECM from "hearing" the signal. Replace it. About $12 at the (a) dealer. https://parts.lakelandtoyota.com/p/_...221935010.html (You'll have to remove the lower intake manifold to do it.)

Originally Posted by JoshThompson View Post
. ... I’ve purchased a used ECM and just waiting to check and see if it fixes the issue. ...
Very, very unlikely to be the ECM. But if it fixes it, hey, there's always a first time.

Last edited by scope103; 03-03-2019 at 11:39 AM.
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Old 03-05-2019, 05:21 PM
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Thank you it was

Originally Posted by scope103 View Post
What does that tell you? That wire (often called the knock sensor "pigtail') is in a hellish environment and often goes bad. The knock signal is a very low level signal, and crappy shielding or insulation will keep the ECM from "hearing" the signal. Replace it. About $12 at the (a) dealer. https://parts.lakelandtoyota.com/p/_...221935010.html (You'll have to remove the lower intake manifold to do it.)

Very, very unlikely to be the ECM. But if it fixes it, hey, there's always a first time.
As I said in the original post. The knock sensor and the harness were both replaced with brand new ones.
Any other ideas?
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Old 03-05-2019, 05:57 PM
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Originally Posted by JoshThompson View Post


As I said in the original post. The knock sensor and the harness were both replaced with brand new ones.
Any other ideas?
Do you know how they checked the signal all the way back to the ECM? If they just verified continuity from the pigtail back to the ECM pin, that wouldn’t be enough and it would take the knock sensor out of the troubleshooting loop. New knock sensors can be defective.
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Old 03-06-2019, 11:08 AM
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Knock sensor issue still


This is what the mechanic said
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Old 03-06-2019, 10:06 PM
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Originally Posted by JoshThompson View Post

This is what the mechanic said
You may want to list the specifics on what exact vehicle you’re dealing with. Did I miss that? I wouldn’t want to assume, since it is at a mechanic, but voltage to the ECM, ECU, PCM, whatever you want to call it, doesn’t guarantee the correct signal is being seen by the computer. If previously manipulating the wiring got rid of the code, I’d focus on that.
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Old 03-07-2019, 07:41 PM
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89 3.0 4runner

89 4runner 3.0
same problem “drunkguy” had

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Old 03-07-2019, 08:00 PM
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You’re probably looking at running a new shielded wire all the way back to the ECM as a next step. There’s plenty of threads on it here. My wiring in my ‘88 was in terrible shape, even the section that was buried in the main harness.
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