Code 52, knock sensors, brand new OEM wiring harness

[tsupranami]

I'm confused. Everyone claims this code 52 knock sensor problem is a deteriorating wiring problem.

However, I just finished a complete OEM Toyota rebuild (new short block, head, cams, everyfreakinthingIswear except cps!) including two new knock sensors and a complete new OEM Toyota engine wiring harness. I am getting the ubiqutous code 52. If this is a problem with deteriorating wiring, why is mine getting this code. This wiring harness is only four months out of the Toyota bag.

Surely there must be some other answer. New Supras didn't have this problem, or did they? My other 89 (white) was running over 300rwhp for more than 5 years w/o any code 52 problems.

I actually had this wiring harness on my white car till May, when the motor let go. I bought the burgandy one May4th, built the motor, and swapped the wiring harness from white to burgandy.

Now I get code 52?!

Please, someone, anyone, enlighten me. I understand the microphone concept and the piezoelectric signal sent from vibration induced deformation, but how does this relate to new Supras, or ones with all brand new OEM Toyota parts? Why didn't they throw code 52's from the day they rolled off the factory floor if the stock wiring was so inadequate?

Anyone dare to venture further into this problem? To me, it would appear that the much touted Schaeff (sp?) rewire solution is actually making up for some other shortfall in the system that still remains in all such rewired cars.

It would appear that there is some sort of electronic interference issue that is being left unresolved by the rewire solution.

 

[ForcedTorque]

The TSRM list possible causes for all the codes. Almost every one of them lists the last thing to check being the ECU.

 

[zachm611]

is it possible for it to be the wrong sensors im not sure but i heard the N/A and turbo ones were different. have you tried your old knock sensors?

 

[tsupranami]

The car was running fine when we took it apart in May, all stock, no codes. I have tried the ECU from my white 89 that we have owned since 1996. It shows the same code after running for a while. The knock sensors are new Toyota OEM. Yes I tried the old ones, same results. The new ones are for a Turbo, not an N/A.

It would appear that it happens more frequently when the car gets hot. If I start it and run it from cold, it hardly ever triggers the cel. However, if I do a lot of stop and go driving where the car gets turned off then restarted, it occurs much more frequently.

It happens usually at cruise, or mild deceleration, never under hard acceleration. It usually happens between 25-55mph, straight or cornering, no difference.

I just removed the sensors, scraped the OEM paint from the block where they screw in, retightened, and tested again. And I quadruple checked the wiring for pinches, cuts, anything out of the ordinary, but alas, all appears to be in perfect place and order. And of course it came on at about 40mph in 3rd while at a steady throttle cruise.

I have ordered a new Cam Position Sensor, as mine has some shaft wobble and is making some abnormal mechanical noises.

Maybe there is some electrical interference from the cps, or even the mechanical knocking of the shaft wobble is hitting the sweet spot for the sensors 7Khz trigger?

Anyways, I'm gonna give it a try and see if I can't find the true cause of the code 52 problem.

As I said before, deteriorated wiring might be an acceptable diagnosis if the wiring is the 20+/- year old original.

But not brand new Toyota OEM wiring on a new Toyota OEM short block with new OEM knock sensors. There must be something else I (we) have overlooked.

 

[enjoi.this]

More then likely a dead short in the wiring, even though its new check it out. If one of the knock sensor wires were pulled on during your swap, that would cause it.

 

[tsupranami]

More then likely a dead short in the wiring, even though its new check it out. If one of the knock sensor wires were pulled on during your swap, that would cause it.

Do you mean an open circuit from a loose or disconnected wire? As I understand it, the sensor sends a small, variable voltage signal based on vibrations from the motor stimulating a piezoelectric element in the sensor.

So any inturruption of this signal, or a signal with a specific frequency (i.e. knock), would set off the cel.

That means I could have a loose wire in the connector, possibly from pulling during the swap? This would seem logical.

I'll check it out tomorrow after the motor cools (and my latest cuts, scrapes, burns, and scalds have scabbed over).

 

[enjoi.this]

Do you mean an open circuit from a loose or disconnected wire? As I understand it, the sensor sends a small, variable voltage signal based on vibrations from the motor stimulating a piezoelectric element in the sensor.

So any inturruption of this signal, or a signal with a specific frequency (i.e. knock), would set off the cel.

That means I could have a loose wire in the connector, possibly from pulling during the swap? This would seem logical.

I'll check it out tomorrow after the motor cools (and my latest cuts, scrapes, burns, and scalds have scabbed over).

Your thinking too hard, check the plugs connection and the wires condition. once the motor heats up --> heats up wire, then wire expands. bam open ciruit tripping code 52. Look closely along wires for discoloring and if its strechy in any spots. Check the rear knock sensor and wiring again.

 

[tsupranami]

Well, it was the rear knock sensor. Maybe it was dropped sometime between builds, who knows. Replaced it w/another new one and cel gone for two days and 200 miles now.


As I suspected, wiring was not my problem. Smart ECU, stupid owner. Now thats a common Supra problem!

 

[shaeff]

Glad that you found the issue. I was going to state that if your wiring is good, (as it should be with a new harness!), then one of your knock sensors is toasted.

Also, turbo and N/A knock sensors are the same.

P/N: 89615-30020

http://cygnusx1.net/Supra/Library/EPC/291410/Parts/89615.aspx