1987 Toyota Supra Knock Sensor issue

  • 6 CYL
  • 2WD
  • 100,000 MILES
I have a 1987 Toyota Supra Turbo (MKIII), the check engine light dashboard lamp has been lighting up approx 15 to 60 seconds after the motor is started. The light will come on sooner rather than later, if I put a load on the motor.
The following are the checks I�ve done and their results:
I put a load on the motor while listening for sounds and found no detectable knock or ping coming from the motor. There is, however, an exhaust leak where the exhaust pipe meets the turbo, but I don�t believe that would cause the sensor to activate.
I believe this model has an OBD 1 computer. When I did the diagnostic code check, the trouble code read out was #52, which indicates it�s a front side knock sensor. I removed the computer and both knock sensors from a friend�s 1987 Supra Turbo and tested them on my car. They had the same part numbers as the parts from my car. When in my car they functioned the same as my parts and presented the same check engine trouble light and knock sensor code number. This would indicate that my car�s parts are functioning well and that the sensor connectors are not bad.
With an advanced ohm meter I checked the communication lines by back probing from the sensor to the computer, they checked out OK with no readings below normal. Also, I tested my computer and sensor, I got the right input and received the right output values.
I�m perplexed. Is there anyone who has knowledge of this type of OBD 1 computer knock sensor problem or any similar OBD 1 issue? If so, please let me know how it was resolved. Thanks.

I�d prefer to try your service before I donate.
Do you
have the same problem?
Friday, February 19th, 2010 AT 12:44 PM

1 Reply

That is a very common problem with the mark 3 supras you have to rewire it not replace it. The wires get shorted out and you have to route them a little differently.
Was this
Wednesday, April 21st, 2010 AT 7:47 PM

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