Knock Sensor Bad?

[myamiphil]

I have a 200 Outback wagon. Over 90,000 miles. Never got to do the
timing belt change yet. Now the Check Engine light is coming on. Error
codes report a defective knock sensor. (not Adjusting) I never heard any
knock yet. Engine is running fine, mileage is decent. Ive been using
regular gas (not brand name) since I got the car. (Shell is a rare treat
these days)

Anyone ever have to change theirs? Wher is it on the engine? Im
imagining somewhere on the top of the block.

Im thinking of bringing it in to do the belt, change the sensor and
while they are at it, change my lower coolant hose and thermostat that I
couldn't change when I changed the upper hose. The sensor is around $300
so they say. Sounds a lot for a sound transducer (microphone?).....

Phil

 

[hyundaitech]

Sounds par for the course. I've replaced a few. They're on the block
toward the back on the left side.

 

[Ed P]

I have a 200 Outback wagon. Over 90,000 miles. Never got to do the
timing belt change yet. Now the Check Engine light is coming on. Error
codes report a defective knock sensor. (not Adjusting) I never heard any
knock yet. Engine is running fine, mileage is decent. Ive been using
regular gas (not brand name) since I got the car. (Shell is a rare treat
these days)

Anyone ever have to change theirs? Wher is it on the engine? Im
imagining somewhere on the top of the block.

Im thinking of bringing it in to do the belt, change the sensor and
while they are at it, change my lower coolant hose and thermostat that I
couldn't change when I changed the upper hose. The sensor is around $300
so they say. Sounds a lot for a sound transducer (microphone?).....

Phil

Phil,

I had to replace the knock sensor on my '96 Outback 2.5L at about 60k
miles. Check Eng lite code indicated the sensor but no other symptoms.
The dealer charged me $43.05 plus tax in June, 2003, for Part #
22060AA031.

The sensor is located on the top left side behind the intake runners and
is held down by one bolt that goes through the center of the sensor,
which has a single wire coming from it.

EdP

 

[JWC]

I'm pretty sure the 'Knock' sensor you mention is actually a "NOx" sensor,
which is part of the emissions control system. NOx stands for nitrogen
oxides, which are a mix of greenhouse gases that contribute to ground
level ozone, acid rain, smog, and can cause respiratory problems. For
these reasons, our vehicles are subject to pretty strict emissions control
standards for NOx and other tailpipe pollutants.

 

[Todd H.]

I'm pretty sure the 'Knock' sensor you mention is actually a "NOx" sensor,
which is part of the emissions control system. NOx stands for nitrogen
oxides, which are a mix of greenhouse gases that contribute to ground
level ozone, acid rain, smog, and can cause respiratory problems. For
these reasons, our vehicles are subject to pretty strict emissions control
standards for NOx and other tailpipe pollutants.

There are also knock sensors which feed the engine controller. AT
least in one generation, they were actually fed by microphones
listening for knock, and adjusting fuel/air mix dynamically in
response.

 

[Todd H.]

There are also knock sensors which feed the engine controller. AT
least in one generation, they were actually fed by microphones
listening for knock, and adjusting fuel/air mix dynamically in
response.

Found a web page that talks about this in more detail:
http://home.netcom.com/~bsundahl/knock/sound/KnockSounds.htm

Very cool stuff.

 

[myamiphil]

Found a web page that talks about this in more detail:
http://home.netcom.com/~bsundahl/knock/sound/KnockSounds.htm

Very cool stuff.

Thanks guys.... THis time it is the knock sensor.... not the NOx
sensor.... THe website sounds interesting. THe software too.... THanks....

Now I have to look into why I can't find a knock sensor online for the
2000 models..... and my dealer wants to charge a lot. PLenty of sensors
for years before 2000. THe 98 models had a tech bulletin regarding
changing the sensor and reprogramming the computer. I wonder if they
fixed it in 2000? Hmmm....

 

[Todd H.]

Thanks guys.... THis time it is the knock sensor.... not the NOx
sensor.... THe website sounds interesting. THe software
too.... THanks....

Now I have to look into why I can't find a knock sensor online for the
2000 models..... and my dealer wants to charge a lot. PLenty of
sensors for years before 2000. THe 98 models had a tech bulletin
regarding changing the sensor and reprogramming the computer. I wonder
if they fixed it in 2000? Hmmm....

This is a guess, but perhaps aftermarket hasn't caught up for the
2000-2004 generation of engines. The 99 and prior models were quite
different. You may be stuck having to get a Subaru part.

Best Regards,

 

[jeff]

Thanks guys.... THis time it is the knock sensor.... not the NOx
sensor.... THe website sounds interesting. THe software too.... THanks....

Now I have to look into why I can't find a knock sensor online for the
2000 models..... and my dealer wants to charge a lot. PLenty of sensors
for years before 2000. THe 98 models had a tech bulletin regarding
changing the sensor and reprogramming the computer. I wonder if they
fixed it in 2000? Hmmm....

Try looking here:

http://www.trademotion.com/partloca...21&make=32&model=Legacy&year=2000&catalogid=1

Jeff

 

[David]

I haven't followed all the links or read the thread carefully, but on some cars
you can get spurious knock-sensor trouble codes. Did you try clearing it
and seeing if it comes back?