Knock sensor

gezzar · Post by **gezzar** » Wed Apr 13, 2011 5:17 pm

Hi all hope someone can help me i have a 2001 Liberty and had the misfortune to get some bad fuel .I have run about 5 tanks of fuel through it but i get the engine managment light flash on at different times ie hot cold .Had the fault codes read and it says the knock sensor .I have changed the fuel filter and was wondering if anyone has any thing i could try .Im thinking maybe the injectors are dirty so run some injector cleaner through the old girl but just the same .I no how the knock sensor works but maybe on a liberty its a fault you guys no about hoping you can help thanks

YouTube · Post by **El_Freddo** » Thu Apr 14, 2011 8:34 am

Have you reset the ECU?

This can be done by leaving the battery disconnected over night. When you initially start the engine do not touch the throttle pedal for a couple of minutes as the ECU will be checking everything out for the want of a better description. Also a good time to check the knock sensor is connected properly, its mounted under the intake manifold at the back of the engine on the passenger's side - a black round thing with a bolt through it and a wire. Make sure the bolt is done up (I'm sure it will be) and that the wire is securely connected.

If the resetting of the ECU doesn't remove the check engine light and thus the knock sensor code, replace the knock sensor.

Cheers

Bennie

Post by **Alex** » Thu Apr 14, 2011 8:59 am

mate buy a new knock sensor. Bought mine off ebay for 120. I literally just changed mine out after having the same problem in my 02 lib.

alex

niterida · Post by **niterida** » Thu Apr 14, 2011 12:07 pm

I'd reset the ECU first - have a search on here for the procedure - no need to disconnect the battery or leave it overnight.
Then if the knock sensor fault reappears then replace the knock sensor.
Note that a knock sensor code doesn't mean it has sensed knock - it means that the sensor has given a voltage reading outside of itw working parameters - in other words it is faulty.

gezzar · Post by **gezzar** » Fri Apr 15, 2011 9:15 am

Thanks for all your help every one looks like its faulty so will get one thanks again .for all your help.

gezzar · Post by **gezzar** » Fri Apr 15, 2011 9:28 am

Thanks for all your help every one looks like its faulty so will get one thanks again .for all your help.

gezzar · Post by **gezzar** » Fri Apr 15, 2011 10:00 am

Thanks for all your help every one looks like its faulty so will get one thanks again .for all your help.

littlewhiteute · Post by **littlewhiteute** » Fri Apr 15, 2011 5:47 pm

littlewhiteute · Post by **littlewhiteute** » Fri Apr 15, 2011 5:55 pm

niterida wrote: Note that a knock sensor code doesn't mean it has sensed knock - it means that the sensor has given a voltage reading outside of itw working parameters - in other words it is faulty.

Not necessarily, the engine could have been knocking after the ecu has removed as much timing as it's programmed to do.
At that point the ecu will log knock sensor codes. The ecu is saying the engine is still knocking after it's done its job.

niterida · Post by **niterida** » Fri Apr 15, 2011 6:32 pm

littlewhiteute wrote:Not necessarily, the engine could have been knocking after the ecu has removed as much timing as it's programmed to do. At that point the ecu will log knock sensor codes. The ecu is saying the engine is still knocking after it's done its job.

I have just reread the Subaru service manual for knock sensor codes and I do not believe that to be true. Knock sensor error code means a faulty knock sensor or least a faulty connection. It doesn't say anything about checking for an abnormally noisy engine. MY RS Liberty to used to go into retard all the time because it had such noisy lifters but it never gave a knock sensor error code. As soon as I moved the knock sensor from the block to the intercooler mount it never went into retard so that prves it was sensing knock and retarding the ignition without giving a knock sensor error code.

gezzar · Post by **gezzar** » Fri Apr 15, 2011 6:45 pm

Thanks mate thats a big help will get the meter on it and see .

greywarden · Post by **greywarden** » Tue May 10, 2011 5:08 pm

Alex wrote:mate buy a new knock sensor. Bought mine off ebay for 120. I literally just changed mine out after having the same problem in my 02 lib.

alex

El_Freddo wrote:Have you reset the ECU?

This can be done by leaving the battery disconnected over night. When you initially start the engine do not touch the throttle pedal for a couple of minutes as the ECU will be checking everything out for the want of a better description. Also a good time to check the knock sensor is connected properly, its mounted under the intake manifold at the back of the engine on the passenger's side - a black round thing with a bolt through it and a wire. Make sure the bolt is done up (I'm sure it will be) and that the wire is securely connected.

If the resetting of the ECU doesn't remove the check engine light and thus the knock sensor code, replace the knock sensor.

Cheers

Bennie

Cool really helpful search button. So far i don't have any questions yet since i will just be leaving my car with the battery disconnected overnight.
well i wish i could find that kind of low price again for the knock sensor. so far i cannot find any.

do we have any seller in here for the knock sensor function?

littlewhiteute · Post by **littlewhiteute** » Tue May 10, 2011 5:49 pm

Just be wary there is a torque specification for the knock sensor bolt.

littlewhiteute · Post by **littlewhiteute** » Fri May 13, 2011 8:09 pm

niterida wrote:I have just reread the Subaru service manual for knock sensor codes and I do not believe that to be true. Knock sensor error code means a faulty knock sensor or least a faulty connection. It doesn't say anything about checking for an abnormally noisy engine. MY RS Liberty to used to go into retard all the time because it had such noisy lifters but it never gave a knock sensor error code. As soon as I moved the knock sensor from the block to the intercooler mount it never went into retard so that prves it was sensing knock and retarding the ignition without giving a knock sensor error code.

That doesn't prove anything really, I've seen engines log knock sensor codes for noisy valvetrain, ends up being worn lifters AND camshaft, after the car has had knock sensors and ECMs replaced.

Also proves Subarus can't disguish between engine noise and abnormal combustion.

I've been in the auto game for 30 years, you can believe what you like, but I've yet to hear of anybody moving their knock sensor for any reason.