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Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14505
Experience:  Toyota Master Diagnostic
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1992 Toyota 4runner 3.0 3vze. Code 52, already replaced with

Customer Question

1992 Toyota 4runner 3.0 3vze. Code 52, already replaced with a new knock sensor and small jumper harness. I bypassed the main harness with a temp wire going straight to the ecu, still did not fix the code. Replaced the ecu with a known good ecu, still get the same code. I reset the check engine light, it runs good when its cold, as soon as I take it out for a test drive the code pops on at around 1500-2000 rpm. Just code 52, no other codes present. I just had the coil/igniter go out, replaced that with a good working one. I checked all vacuum hoses, they are in good shape with no leaks and in their proper spot. Any ideas on where to start from here?
Submitted: 7 years ago.
Category: Toyota
Expert:  Skyvisions replied 7 years ago.

Where did you purchase the knock sensor and sub wiring harness from? When you used a bypass wire did you clip the wire and tie it to the stub going into the computer and at the sensor? In other words was this separate wire totally independent from sensor to the computer? Did you check the pin fits to make sure the female pins are tight at the computer and at the sensor?



Customer: replied 7 years ago.
New sensor and harness came from Toyota. I had another junk harness that I cut the pin from and ran a complete new wire to the ecu. I tested it with a multimeter and the wire is fine and I am getting a good connection. Is there any other sensor that is tied to the knock sensor that would throw a code 52? I am a experienced mechanic and have worked on a lot of the 3.0's. I know its usually the sub harness that is bad, but its new and I tested it. Knock sensor is new. Swapped the ecu with a good ecu. I also tested the original harness with a multimeter, its checks out good, just to be sure I ran a new wire to the ecu, removed the pin from the ecu, and installed a pin from the junk harness. Every thing I read says its 3 things: bad harness, bad knock sensor, bad ecu. I am taking the knock sensor back to toyota today and am going to exchange it for another one to see if thats it. I did try another old knock sensor that I had laying around and it still popped the code. I just dont get it. Everything I have tried should have fixed it or pointed me in the right direction unless there is some other non documented function that is linked to the code 52.
Expert:  Skyvisions replied 7 years ago.

There is no other inputs or wires on this line for this system. If you're getting a code 52 the only way this can happen is if there is an open or short in the signal going to the computer. The info wire is a shielded ground signal wire. Do you have an oscilloscope to actually test the signal at the computer? Did you test the integrity of the signal wire to ground to make sure that there was no short in the ground to signal wire? This should not be an issue if you ran and entire separate wire from the sub harness into the computer. This is normally. What I do when I suspect the issue in the original factory harness, totally cut out the factory harness between the computer and the knock sensor. I normally use shielded coaxial cable from RadioShack. If you are certain that this wire was not interfered with or the signal was interfered with by electro-forces from inside the engine compartment because it was not shielded to ground than that only leaves the option of a bad sensor or sub harness. Normally what I do is put oscilloscope on the wire at the computer then use an air hammer and slightly vibrate the base of the block next to the sensor to see if you can create a signal input to the computer.



Customer: replied 7 years ago.
Sorry, but your answer did not help. I already tried those things. I did find out what the problem was, it was a bad distributor. I replaced the distributor and the code went away. It did not make sense to me, but thats what worked.
Expert:  Skyvisions replied 7 years ago.

You're right that makes absolutely no sense. Not even remotely connected. At least you got the car running. Happy new year.