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BigBob
BigBob, Shop manager/Service Manager
Category: Toyota
Satisfied Customers: 4838
Experience:  Shop Manager with 25 years experience
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93 3.0 v6 has code 25 and 52, how do you check the knock sensor

Customer Question

93 3.0 v6 has code 25 and 52, how do you check the knock sensor and where is it located. already replaced o2 sensor. has a rough idle and smells like it is running way to rich
Submitted: 7 years ago.
Category: Toyota
Expert:  BigBob replied 7 years ago.
Greetings,

The Knock Sensor is located on top center of the engine block under the Intake Manifold.

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1. Disconnect the knock sensor connector and check for a key on engine off reference voltage of 0.015 to be applied from the Electronic Control Unit (ECU).

2. Check for AC output voltage on a lab scope coming from the knock sensor during crank. A very small amount of voltage should be present.

3. Revving the engine between 3500 and 4000 RPM, a frequency reading of 7000 to 8000 Hz should be coming from the knock sensor

The wire harness is a common problem for this code after head gaskets have been replaced. Chances are extremely good that the harness under the intake has a few broken wires. Knock sensors rarely fail


let me know if I can help further.

Good luck,

Bob

BigBob and other Toyota Specialists are ready to help you
Customer: replied 7 years ago.
i found the knk sensor wiring diagram in the haynes manual but not real sure which connector it is, sometimes these manuals are not real clear. would the broken wire cause the rough idle?
Expert:  BigBob replied 7 years ago.
Usually the knock sensor will not cause a rough idle, but if it has spark knock or pinging then it could. We have had cases where the rough idle clears up when repairing the wiring harnes and or knock sensor. My manual does not show the connector, but it should rundown the middle of the intake, and there should be a connector from there.


Bob