Hi

I just picked up an 91 turbo sports sedan (http://forums.nasioc.com/forums/showthread.php?t=1165246#). And just after i got it the check engine light came on. So i did some research and pulled the codes with the 2 connectors under the dash. There where 2 codes 1 was an knock sensor. And the other is an atmosphric pressure sensor. And ive also tryed clearing these codes both ways trying the dissconnection the battery method and the other method where u mess with the shifter anyway i cant clear them so the much be hard faults. Now the question is is where is this knock sensor located? and should i just replace it? and where is this atmosphric pressure sensor located and is there anyway to adjust it or something? thanks for reading guys i could use some info.:confused:

Is this a US based car?

If you look straight down at the throttle cable area, you should see the knock sensor. In this pic, it's the black round sensor with a bolt through the middle and the white electrical connector.
http://www.main.experiencetherave.com:8080/subaru/images/injectors/DCP_2481.JPG

More pictures for your viewing pleasure :)
http://www.main.experiencetherave.com:8080/subaru/images/injectors

As for the other code. Code 45 on the turbo cars is related to the pressure sensor and/or pressure exchange solenoid.

I would check the resistance of the knock sensor, and see if it is within spec.

Same goes with pressure/pressure exchange solenoid.

If they're outside of spec, replace them, and you should be able to clear the codes.

I'd also suggest checking out www.bbs.legacycentral.org