View Full Version : Knock Sensors

07-04-2005, 05:59 PM
A while ago, I ran my Peake Fault Code Scanner on my car just to see if anything was showing up, even though the CEL wasn't lit. It came back with the code '2A' (I think). It was the code for the knock sensor.

I ran it yesterday to see if it was still showing up and now it is gone. Now I have the code 'CF' for ' Knock Control Regulation'.

What does 'KCR' mean...and would replacing the knock sensor solve it?

Can anyone give me some insight on replacing a Knock Sensor? I read some on BF.C, but it was for an M3, and not a TI. I figured this would be the best place for information regarding the TI application.

Also, what does a Knock Sensor do?

Come on guys...surely someone knows something about a KS?

07-05-2005, 09:07 PM
I have a 95ti and I can tell you that it does have them. I say them becuase I recall the dealer's mechanic telling me that there was more than one, two if I'm not mistaken. The knock sensor keeps your car running smooth during advanced timing when the timing is slightly off TDC , you can often hear the knock or pinging sound like rocks in a can such, as when you use cheap gas and the car shutters. The sensors also keep your spark, the air-fuel mixture, and valve opperation in sync by sending signals to the computer. If your knock sensors are not working you can damage the engine components like the pistons, valves, spark plugs and more. I too had the code appear when I took mine in for a routine diagnostics, I was quoted $900 by the dealer and $600 by another BMW service shop. I didnt have it done becuase mine ended up being from my wife putting 94 octane in the gas along with gas treatment that bosted the octane another 4 to 5 octane. Basically It was damn near like running StreetBlaze race fuel. After the next refill of 93 octane my code cleared, but my solution may not be yours. Good luck and keep us posted.

07-06-2005, 02:06 AM
thanks guys...

i called the shop today for some advice...and he said that knock control regulation just basically means to replace the knock sensor...

my car has been running rough the last few days...it may be beause bad gas? im not sure...ill see if its still a bit rough after next refill...then i guess ill have to try and get it done myself...or get the shop to do it (yikes...600...damn my car is adding up now...)

it seems like a fairly major job...but i cant really afford 600 :(

07-16-2005, 07:07 PM
no one knows how to change knock sensors...the mechanic said he has changed two in the last twenty years and that they usually arent a problem.

i have since refueld my car and it runs MUCH better...havent checked for the code yet, but it seems like it wasnt really a problem

and now i went to the library to get my 3 series haynes repair manuel....and it is no longer available...they got rid of it! iwas aboyt the only person to pick that book up! why didtn they just give it to me gosh darnit!

07-16-2005, 08:48 PM
if you could afford the knock sensor, you could afford to buy the haynes or bentley manual :p

as you found, it pays to get quality gas (ie, not the cheapest). i tend to buy from one of the majors and try to get it from a busy area (quicker turnover of gas).

12-13-2005, 09:19 PM
I have a 95 TI that my wife says pings, I had her switch to 93 and it helped but on hot days on a grade it still pinks a tad. According to her. It may have a knock sensor issue too, I have yet to read the codes out. I also wonder if carbon has built up to the point that it is pinging, the CR is so high to begin with I can see how this could happen. Next step is to add some xylene, I do this on my blown Chevy to keep it out of detonation.

12-13-2005, 09:29 PM
my 95 ti doesnt ping any...but it just has the fault code for the knock sensor...i have yet to replace it as it cleared up for a while...but then came back so i have to take care of it soon.

i have the bentley manual now, though it is still kind of vague on how exactly to replace it, but it gives me an idea ya know. that may be my christmas break project!

12-13-2005, 09:34 PM
I'll read mine and see if has set the code.

02-18-2006, 10:07 PM
I did mine a year ago and it involves a lot of work. You need 2 knock sensors, 2 fuel line clamp, intake manifold gasket. There are 2 knock sensors, 1 is visible if you looking down the engine block. The other one is way inside on top of the starter. The top intake manifold has to come off, wiring harness, disconnect two fuel lines , then the lower intake manifold. I replaced both since I am already there.