Question about Subaru Legacy

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Need to locate knock sensor on 1994 subaru legacy gt with the 2 litre twin turbo engine. I have the intercooler off as advised by my mechanic and looking down into the hole its left I can't find it. Pleaase help, thanks!!!

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  • Paul T Apr 29, 2010

    Sorry, I'm being a bit thick I know, but i'm no professional, so if i'm looking down onto the engine block from the front of the car the KS pretty much central on the back of the block, is that right??? Thanks

  • Paul T Apr 29, 2010

    Good advice so far but can't see it, would there be more pipes to move etc ?

  • Paul T Apr 29, 2010

    thats good thanks but my GT has like the rectangle black radiator (called the intercooler I think)ontop under the air scoop in the bonnet and I have removed this and disconected most of the hoses, throttle body on left as seen from from front (drivers side) so will the KS still be under the throttle body? Sorry for being so slow...! Thanks

  • Paul T May 05, 2010

    Really helpful advice, found it in the end thanks!!!

  • Paul T May 05, 2010

    Really helpful advice, found it in the end thanks!!!

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3 Answers

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  • Subaru Master
  • 17,970 Answers

For 1994 Subaru Legacy 2.2L MFI Turbo 4cyl the Knock Sensor is located under hood, center, upper engine area, mounted on rear of engine block.

OPERATION

When knocking occurs, the weight in the cylinder case moves, causing the piezo electric element in the KS to translate the vibration into an electric voltage. A signal is then transmitted from the KS to the ECU. In response, the control unit retards spark timing to prevent engine knocking.
On the Loyale with Multi-Point Fuel Injection (MPFI), the KS is located on top right-side of the cylinder block and senses knock signals from each cylinder.
On the Legacy and Impreza, the KS is installed on top left-side of the cylinder block and senses knock signals from each cylinder.
The SVX is equipped with 2 knock sensors; both are located on top of the cylinder block-one on the right side and one on the left side.


TESTING (Legacy, Impreza and SVX)
(see Figure 1)


Need to locate knock sensor - ec0bf10.jpg

Fig. 1: Testing the knock sensor

  1. Disconnect the KS harness.
  2. Measure the resistance across the KS terminals.
  3. The resistance should be approximately 560 kilo-ohms.
  4. Replace the KS if the resistance is out of range.

Problem: The Check Engine Light appeared, and the car lost power while driving. After a few minutes, the light went off and the car felt normal again. Diagnostic confirmed knock sensor error.

Solution: Replace the knock sensor.

Tools required:
1/2" Wrench
1/2" Torque wrench
13 mm pipe and angled connector
10 mm spanner

Estimated time (10 minutes):

The knock sensor is located under the left rear intake manifold runner (for cylinder No. 4), on top of the engine block, to the left of the engine. The knock sensor monitors engine vibration caused by detonation. Basically, a knock sensor converts engine vibration to an electrial signal.

When the knock sensor detects a knock in one of the cylinders, it signals the PCM so that the PCM can ****** ignition timing accordingly.

The knock sensor contains a piezoelectric material, a certain type of piezoresistive crystal, that has the ability to produce a voltage when subjected to a mechanical stress. The PCM doesn't respond to the knock sensor's input when the engine is idling; it only respons when the engine reaches a spesific speed.

- Disconnect the negative battery cable.

- Locate the knock sensor retaining bolt.

- Disconnect the knock sensor plug.

- Make a visible mark, so that you can install the new knock sensor in the same angle.

- Insert the pipe and remove the knock sensor retaining bolt, and the knock sensor.

- Install the new knock sensor, using the same position (the pigtail harness should be at approximately a 60-degree angle to the back of the engine, but using the mark you made is fine) as the old sensor.

- Tighten the knock sensor retaining bolt to the correct torque, 209 in-lbs (23.6 Nm).

- Connect the battery and your done.


Hope thats help.

Posted on Apr 29, 2010

  • ZJ Limited
    ZJ Limited Apr 30, 2010

    No you don't its very easy to replace. Use a few extensions on a 12 or
    might have been 10mm socket. Remove bolt, and pull out sensor. Carefully
    unplug the connector!



    When you put the new sensor in be sure to not tighten the bolt very
    much. The torque spec on it is something like 13-15ft-lbs. Or you can
    basically go snug.

    +1 on the be careful when tightening the sensor...
    it's WAY too easy to crack the housing.....



    I suggest check this TSB for Subaru Legacy

    Good luck.


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  • Master
  • 5,081 Answers

It is underneath the intake manifold. If you look straight down from your throttle body, you will see a sensor with one wire coming out and a bolt going through the middle of it, that is the knock sensor.

http://webcache.googleusercontent.com/search?q=cache:yCxk_L1QRRMJ:www.lovehorsepower.com/SubaruDocs/subaru_legacy_knock_sensor.htm+locate+knock+sensor+on+1994+subaru+legacy+gt&cd=1&hl=en&ct=clnk&gl=in&client=firefox-a

Check the above link it might be useful.

Posted on Apr 29, 2010

  • INDIRA KUMAR
    INDIRA KUMAR Apr 29, 2010

    http://webcache.googleusercontent.com/se...

    copy the above URL and paste it in your address bar and you will get picture wise explanation...

    Donot forget to rate and accept my answer...


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  • Master
  • 15,935 Answers

Under hood, center, upper engine area, mounted on rear of engine block.

Need to locate knock sensor - 7e83fc8.jpg

When knocking occurs, the weight in the cylinder case moves, causing the piezo electric element in the KS to translate the vibration into an electric voltage. A signal is then transmitted from the KS to the ECU. In response, the control unit retards spark timing to prevent engine knocking.

On the Legacy and Impreza, the KS is installed on top left-side of the cylinder block and senses knock signals from each cylinder.

  1. Disconnect the KS harness.
  2. Measure the resistance across the KS terminals.
  3. The resistance should be approximately 560 kilo-ohms.
  4. Replace the KS if the resistance is out of range.

REMOVAL & INSTALLATION

  1. Disconnect the negative battery cable.
  2. Disconnect the KS wire harness.
  3. Loosen and remove the sensor retainer bolt, then remove the sensor.

To install:
  1. Position the KS on the engine block, and secure in place with the retainer bolt. Tighten the bolt snugly.
  2. Connect the sensor wire harness.
  3. Connect the negative battery cable.
Thanks for using FixYa!!

Posted on Apr 29, 2010

  • blueextc3221
    blueextc3221 Apr 29, 2010

    top of engine.... dead center.



    It looks like a small doughnut

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