Knock Sensor

[extremetoy2000]

I have a 1992 sc400. It runs great for a short time. Then the Check Engine light comes on and it looses power. It still runs it just has a noticeable power loss. The code reade show a fault code of 52. I believe this is a knock sensor. What I need to know is how difficult this is to replace and is there any thing else that would be causing this problem before I replace the knock sensor.

 

[GSMnow]

Most likely, your ECU is never seeing a knock signal from the sensor. This is a fault as it should show at least a little ping under hard acceleration. Since it sees no knock, it assumes the sensor is bad an retards the timing to be safe. The first place to start is to probe the wiring from the sensors to the ECU to see if there is possible a broken or grounded lead. If the wiring checks out, you need to check the sensors themselves. The check procedure in the book calls for a scope to see the waveforms. I don't have my books available, so hopefully someone else can help you with the location of the sensors. There should be one in each bank, I think they are either in the side of the block just under the head, or they could be in the "V" under the intake. On most engines, they locate the knock sensor as close as possible to the deck surface. If it has a code for each bank, you may be able to swap the sensors and see if it then gives the code for the other bank.

Gary M.

 

[extremetoy2000]

Thanks for the info. I think the sensor is under the intake manifold and the gaskets are expensive, which is why I wanted to try all other possibilities first.

 

[gloverman]

The Knock sensors are under the manifold in the valley. Their wiring comes out the back with the starter wiring. They are not that hard to get out. Cheers

 

[V8superlux]

Check the wiring all the way to the knock sensor before condeming the sensor. I have seen plenty of 1UZ's log a knock sensor code but I have never had to change one. The most common fault that I have come across is rats and mice eating the insulation off the knock sensor wiring. Don't laugh but for some reason its quite often the only part of wiring in the whole car that they eat (it must taste nice?????).

 

[Lextreme]

An old thread that gets a ton of views from owners looking for help. You might be interested in this video. (LS400 not SC400)