Where's the knock sensor? [Archive] - GrandAmGT.com Forum


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07-03-2005, 03:38 PM
Hi all,

I'm still getting familiar with where everything is on this car.

I've got an '01 2.4 4-cyl. I don't know where the knock sensor is. The car is pinging alot and I've done the usual things: changed the spark plugs, I've used premium gas, etc. I think the next thing to try is the knock sensor, but I don't know where it is. :( I know this sounds like a dumb question, but without my having access to the shop manual for this car, could anyone here give me a quick description of where it is?


07-04-2005, 10:54 AM
I didn't have a 4cyl car but I do still have my Haynes Manual...here's what it said. I'd scan it but I'm at my parents house for the 4th and can't find a usb cord for the scanner, lol. I can always scan it later though.

According to this its on the firewall side of the engine below the exhaust manifold. In their pic they've removed the exhaust manifold. I don't know how tough it is to get to with the manifold in place.

You can test it:

"3. Disconnect the electrical connector from the knock sensor. On four-cylinder models with a two wire sensor, follow the wiring harness from the knock sensor to locate the knock sensor harness connector. Single wire sensors contain an internal 100 K-ohm resistor; on two wire sensors the 100 K-ohm resistor is in the PCM. Using and ohmeter, measure the resistance between the terminal on the knock sensor and the engine block (single wire sensor) or on a two wire sensor, between the two terminals of the sensor connector (harness site, not the sensor side).

The resistance should be approximately 90 to 110 K-ohms. On a single wire sensor, if the resistance is not as specified, replace the knock sensor. One a two wire sensor (harness side), if the resistance is not as specified, check the wiring harness from the sensor connector to the PCM, including the PCM connector fro looseness or damage. If the harness and connections are good, replace the PCM.

4. To check the sensor operation, reconnect the connector to the sensor. On models with a single wire sensor, backprobe the wire terminal at the electrocal connector using a suitable probe. On models with a two wire sensor, backprobe both terminals. On a signel wire sensor, connect the positive lead of a voltmeter to the probe and the negative lead to a good engine ground point. On models with a two wire sensor, connect the positive lead to the dark blue wire and the negative lead to the gray wire. Set the volt meter on the AC volts sacale. Start the engine and check for an AC voltage signal from the knock sensor. The AC voltage should increase as the engine speed increases. If a voltave signal is not present, replace the knock sensor."

Thats the text from my haynes manual. If you're still learning the car it's not a bad idea for $20 to pick one up.

Keep us updated and let us know how it goes. I'd test it before trying to pull it out.

07-04-2005, 10:58 AM
Here's what they say about backprobing:

"If its often necessary to take circuit voltage measurements with a connector connected. Whenever possible, carefully insert a small straight pin (not your meter probe) into the rear of the connector shell to contact the terminal inside, then clip your meter lead to the pin. This kind of connection is called "backprobing". When inserting a test probe into a mail terminal, be careful not to distort the terminal opening. Doing so can lead to a poor connection and corrosion at that terminal later. Using the small traight pin instead of a meter probe results in less chance of deforming the terminal connector."

BTW, excuse any typos. :)

07-05-2005, 08:38 PM
Cool. I've looked around for the Haynes or Chiltons manuals, and I can't seem to find them for my year car. I've only found them for 2000 and earlier, and mine is a 2001. Do you have a Haynes book for '01?


07-06-2005, 06:38 AM
Yes I do, but it has a year range on it, and has a white Malibu on the cover. It covers a bunch of platforms and engines, but will have our year Grand Am listed on the cover. So it's not the greatest but does help.

07-06-2005, 08:11 PM
Can you post the ISBN number?


07-07-2005, 06:36 AM
Not until the weekend - but I will once I get the chance. (It's at my parents house)

EDIT: Nevermind I checked Amazon... :

ISBN: 1563923610


07-10-2005, 06:22 PM
Great. Thanks!