[Square]

Ok, I have been fighting this for months. I have searched the forums, tossed parts at the issue, even hired a shop to try and track it down. Nothing has helped. I really need some sage level help here. 91 MR2 Turbo

My understanding is that code 52 is not a knock issue but a communication issue between the ECU and the sensor itself.

Any time I rev the car past 2000 rpm I get a code 52 on the dash. The car goes into limp mode. I can drive but it feels like the ECU pulled all the timing and the engine bogs down. I can cycle the key and the light shuts off. It comes back again right at 2500ish rpm. I haven't felt turbo pressure in months.

Here is what I have tried so far.

Let the car sit overnight with the battery disconnected. (Attempting to clear stored codes) Check
New Knock Sensor Check
New Shielded Knock Sensor Wiring. New cpu pin connector. New Toyota Knock Sensor connector. Verified the shielded wire is grounded. Check, check, check and check
Another New Knock Sensor, Check ( Who knows, maybe I got a dud.
Verified the block is grounded to the frame. Check
Had a shop check the car over for an electrical drain I was having. The drain was located in the aftermarket stereo.

I also found out the fuel filter was really old. I changed that as well as installed a Supra TT fuel pump and relay wiring upgrade. Again, just checking anything and everything at this point. This helps get me to my power goals of 320ish to the wheels.

I do know that engine is a jdm block. The head/intake/turbo are all usdm. The car also has from what I can tell USDM electronics.

Out of desperation I have now cracked open my ECU. It looks brand new inside. I am not seeing any corrosion or popped caps. At least I don't think these are blown. I do see something that looks like glue between a couple of what I think are Ceramic capacitors. It's hard and bridges between two of them. Are these blown? It doesn't look like any kind of blown capacitor I have seen before working on computers. I have attached some photos. Does this discoloration indicate these are blown or is it just glue?

Sadly I don't have another ECU I could try. If anyone in the Portland Oregon area has a spare to test/buy with I would be very grateful.

At this point I don't know what else I should check. Everything from the Knock sensor pin in the ECU wiring to the knock sensor is new.

I don't have facebook so I can't share this on the Facebook page.

 

[1950884]

I experienced a code 52 with a gforce modified ecu and a new sensor fixed my issue. I think your next step is to swap a known to work ecu. I’d bet it’s the capacitors. I appreciate your tenacity. You’ll figure it out.

 

[rmeller]

... I am not seeing any corrosion or popped caps...

... I do see something that looks like glue between a couple of what I think are Ceramic capacitors. It's hard and bridges between two of them. Are these blown?

The electrolytics can also dry out, so they do not need to have overt signs of failure.

That is encapsulant, sprayed on intentionally. Ceramic capacitors rarely fail in a low voltage application. Same with the plastic film capacitors.

 

[1991 MR2 Turbo]

I don't live in Portland, but I could kinda help you out. If you send me a deposit and pay for the shipping, I can send you out a ecu.. If it doesn't help send back the ecu and I'll refund you the cash. You'll lose out on the shipping unfortunately if it doesn't work for you.

Let me know if this is what you're interested in.

 

[Square]

Thank you for the kind offer. Thankfully I found a great deal on a known working ECU a few hours before you offer came in. If it fixes the issue, great. If not, than I have a backup ECU. Trying to look on the bright side at least.

Thank you for being willing to do that though. That's is very kind.

 

[Square]

The electrolytics can also dry out, so they do not need to have overt signs of failure.

That is encapsulant, sprayed on intentionally. Ceramic capacitors rarely fail in a low voltage application. Same with the plastic film capacitors.

Thank you for the info. I was fairly sure that was done at the factory. It's nice to have a second opinion.

 

[T3HKMAN]

Just blew my oem knock sensor about 6 weeks ago and from the research I did there are a couple of different sensors out there. I ordered these from ebay and it fixed my issue right away. "2 Knock Sensor & Harness FOR TOYOTA 4Runner MR2 For LEXUS LS400 89615-50010" Super cheap and Denso labeled. Also did you pull the 15amp EFI fuse in the engine bay? You have to remove that for 15 minutes to truly clear the code from my reading not just remove the battery. Hope this helps.

 

[Square]

Just blew my oem knock sensor about 6 weeks ago and from the research I did there are a couple of different sensors out there. I ordered these from ebay and it fixed my issue right away. "2 Knock Sensor & Harness FOR TOYOTA 4Runner MR2 For LEXUS LS400 89615-50010" Super cheap and Denso labeled. Also did you pull the 15amp EFI fuse in the engine bay? You have to remove that for 15 minutes to truly clear the code from my reading not just remove the battery. Hope this helps.

Well past the pull the efi fuse. I have also already fully replaced the knock sensor wiring from the ECU pin to the sensor itself. Thanks for the tip though.

 

[1ofthesedays]

KO Racing is close to you. You can try reaching out to them to see if they can take a look if the replacement ECU doesn't fix it.

 

[Square]

KO Racing is close to you. You can try reaching out to them to see if they can take a look if the replacement ECU doesn't fix it.

Yes, that has always been in the back pocket. I hate being beaten by a issue like this. Its the knock sensor. A 1 wire circuit. I normally do all my own work so farming stuff out is almost always a last resort.

 

[1991 MR2 Turbo]

Thank you for the kind offer. Thankfully I found a great deal on a known working ECU a few hours before you offer came in. If it fixes the issue, great. If not, than I have a backup ECU. Trying to look on the bright side at least.

Thank you for being willing to do that though. That's is very kind.

Anytime man, I don't mind helping out.
I wish forums were more alive, it feels more of a community thing.

 

[Square]

Anytime man, I don't mind helping out.
I wish forums were more alive, it feels more of a community thing.

When I had my AW this forum was the place to be. So much activity and a great community. That was several years ago at this point. I was sad to see the switch over to facebook.

 

[bobster99]

OK, this is going back a few years and it is from memory but I had the same problem with mine. If I dove it carefully it would be fine but once I got on it the check engine light would come on and it would go into limp mode. I would just push in the clutch and restart the car and it would be fine until I really stepped on it again. One of the forums I was on said that OEM Toyota Sensors were too sensitive and they suggested replacing the Knock Sensor with one from a GM 350. It isn't a direct bolt in and I think that they re threaded it to fit into the Toyota block. A quick search turned up this and I am pretty sure this is where I got mine.... ATS Knock Sensor - ATS Racing It has worked fine on my car for years now.

 

[mike555]

Can I ask what your setup is? Stock? If modified how much boost are you running? Have you tried disconnecting the boost sensor? (the one on the back fire wall by the trunk). If you dissconnect the boost sensor... plug the small hose going to the intake with a small bolt or something. Try test driving it that way. But like others have said...Get the GM knock sensor or something similar. I think ATS still carries them. The are way less sensetive!!

 

[Square]

Can I ask what your setup is? Stock? If modified how much boost are you running? Have you tried disconnecting the boost sensor? (the one on the back fire wall by the trunk). If you dissconnect the boost sensor... plug the small hose going to the intake with a small bolt or something. Try test driving it that way. But like others have said...Get the GM knock sensor or something similar. I think ATS still carries them. The are way less sensetive!!

Mostly stock. The car came with a fuel cut defender. I have the car set to 14psi of boost with a manual boost controller that also came with the car. Other than that I have a LSD in the transmission.

I have already tried the ATS sensor and had the same problem.

 

[Square]

Can I ask what your setup is? Stock? If modified how much boost are you running? Have you tried disconnecting the boost sensor? (the one on the back fire wall by the trunk). If you dissconnect the boost sensor... plug the small hose going to the intake with a small bolt or something. Try test driving it that way. But like others have said...Get the GM knock sensor or something similar. I think ATS still carries them. The are way less sensetive!!

I disconnected the boost sensor. I plugged the hose. I also took the electrical connector off. The car did the same thing as before. You could start it up, it would idle with no code. As soon as you rev the engine the CEL comes on. I did find out the CEL comes on right around 1800 rpm.

This is with the new ECU in the car as well.

 

[Square]

Dropping the car off at KO Racing Wednesday. I will update this thread with what they find.

 

[Square]

KO racing was able to track down the issue.

Apparently I had been sold 2 faulty knock sensors back to back.

After buying two knock sensors from two different companies. One toyota and one from RockAuto I was convinced the sensor was not the issue. I'm very happy this got resolved but also frustrated at what the issue actually was.

Anyway, Sunday is looking like it's going to be sunny in my area and I plan to take full advantage of that.