Code 52 doesn’t leave me alone

[teedoff00]

I left it alone. I figured I would need to swap one at a time to rule out the problem. Unless both sensors are intermittent. When I swapped the front and the CEL stayed off I assumed that the front sensor must have been on its way out. But now I still get the code 52, however it doesn't throw the code every time I drive it and is much more infrequent. I don't know if swapping the rear for another used would solve this issue?

I really wish we could test these things, I hate not being able to just throw my multimeter on it and say, yup its good. Taking these out and putting them in is such a pain with the limited space.

Any advice appreciated!

 

[DeMoN2318]

You CAN test the sensors but you need an O-scope...and not many people have them.


The ECU basically has a "Code 52 check sequence" that requires a particular amount of time in different rpm ranges. so the inconsistent code 52 intervals is because of this.

The reason you got it right away before, I would guess, is because your sensor was totally bad and sending no signal at all.


You can test the sensors independently (vehicle testing) if you bridge a single sensor to both ECU inputs. Sucks because it requires driving to see if the code come back...and its not the same amount of driving each time.


I wish I knew the check sequence so I could write a vehicle test procedure...but I dont

 

[jetjock]

Lots of ways to test them, from a DMM on up. You can even test both at once by using one to excite the other. I've done it. Requires some gear though. And yes, several parameters must be met before 52 is set.

 

[jony89]

1. make sure you have the right year of ks on your car (my idiot self had 89+ on a 88)
2. make sure your wiring is good.
3. make sure your ground is good.

Go to the junkyard and find some sensors put them in your pocket and walk out if you think your sensor might be the problem haha

clear the ecu every time you change one of those things

 

[teedoff00]

Interesting. Is there a way to test them without screwing them into the block? Just having them connected to the harness and ECU? I guess the variation in RPM might be the weak link to that method... I would just buy two new sensors, but I hate throwing money at a problem, when it could be something else.

JetJock, would you mind elaborating on proper testing procedure with a DMM? I really appreciate the help guys, thanks for the replies.

 

[atmperformance]

I found my block had 3 threaded holes (NA cars use the middle) so i ended up hand tightening 3 sensors on and swapped the connector around, once i replaced my rear KS connector so it would sit firmly on the sensor my problem was solved. I also had a 89+ sensor i tried to use with a 89+ connector wired right into the ecu but still got a code. Use the KS for your year

 

[teedoff00]

Is there a way to tell what year the sensors are from? I couldn't get the light to come on this afternoon even after driving it for quite some time on the freeway at cruise, under wot, around neighborhoods, idling...

This certainly is perplexing...

Thanks for the tips and replies, your time is appreciated.

 

[IndigoMKII]

You can test the sensor by tapping on them lightly with a wrench with a DMM set to dc auto range.

I dont recall the operating range of them though.

 

[teedoff00]

Ok. Does anyone know the correct resistance range?

Thanks for the reply.

 

[DeMoN2318]

Not sure what resistance would really tell you other than if it is shorted or open

The knock sensors use a piezoelectric material that generates a voltage when deformed...so taping on the sensor will create a voltage potential...not a resistance


leave the sensors installed and hook the DDM up to the sensor and tap the block near the sensor...dont hit the sensor, and see what voltgae you get, then repeat but with the DDM at the ecu and see what voltgage you get...

But, I dont think this well tell you much, since you dont know what voltage the ECU needs to see for its Code 52 checks.

 

[teedoff00]

Hmm. So there isnt a way to really test them with any certainty off of the car. And the best way to rule out sensors is to link two connectors or ks1 and ks2 to one sensor and drive it?

Also, can anyone tell me how to tell the difference between the 87/88 and the 89+ sensors? The pair I got were a hair shorter than the one I removed. Maybe its a newer one...

Anyone wanna trade?

 

[jony89]

Hmm. So there isnt a way to really test them with any certainty off of the car. And the best way to rule out sensors is to link two connectors or ks1 and ks2 to one sensor and drive it?

Also, can anyone tell me how to tell the difference between the 87/88 and the 89+ sensors? The pair I got were a hair shorter than the one I removed. Maybe its a newer one...

Anyone wanna trade?

i think, I’m not sure, the 88 and below were green and the 89+ were grey. sounds to me like the wrong sensors. when i put mine on i couldn’t tell the difference just the fact that the 88 clips fit a lot tighter on the sensor and the 88 sensors and clip slide on very easily.

go to the junkyard and find sensors of your year, I’m sure the problem will go away

 

[3p141592654]

The 7MGTE ECUs from 87 through 93 use the exact same knock sensor processor. I doubt there is any difference other than connectors between the various knock sensors for the GTE.

 

[teedoff00]

I'll have to snap a picture of the one I installed and the one I removed. I'll report back.
Also, I may try threading in a third sensor as suggested, even though that would probably mess with the knock metering?

Thanks again for all the helpful replies.

 

[teedoff00]

Ok so this picture is of the grey connector KS I removed and the green connector KS that is the mate to the one I installed.


So it seems I have two sets of KSs, one set from the 87/88 and one set from the 89+. But could that be the issue? It seems like we don't all agree that there is a difference...

The issue is far more intermittent than it was before I swapped in the green KS. Before the CEL came on every time I drove the car, but sometimes was shortly after start, other times well after start. Now I get the Code 52 about every other time I drive it. I went almost 2 days without it coming on.

So what should be my next diagnostic course of action? 87/88 sensor? Redo the wiring yet again? Silly question, but is there anyway to test the wiring?

I appreciate the help guys, I'd really like to figure this out and hopefully this thread will be useful in the future.

 

[jony89]

alright so if your car is an 88 below use the green sensors (if the sensor and wiring is good and clear codes the problem should go away) and make sure your connectors are from the same year. vice versa if its 89+ use the grey sensor etc.

if it comes back you have a problem with your sensors, wiring, or both

 

[hvyman]

I seen someone else a long while ago had issues with the later knock sensors on a early Ecu. Not sure why tho.

 

[IndigoMKII]

Cant we also use knock sensors off another toyota?

 

[DeMoN2318]

Just buy a harness from Shaeff on here...that will rule out the wiring as the issue, he checks and verifys every harness before he ships it.


You can use either sensor, but the plugs have to match or you will have connectivity issues.

 

[teedoff00]

It could be the connectors I suppose, I would assume mine are from an 87 or 88 as I got them from Jeff at Champion when I redid the wiring...
I guess I need to track down some 87/88 knocks to test. And I may have to hit Shaeff up for a wiring harness.