Knock Sensors - Bimmerfest - BMW Forums



Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series & 4 Series > E46 (1999 - 2006)

E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

Reply
 
Thread Tools Display Modes
  #1  
Old 06-11-2019, 01:45 PM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
Knock Sensors

Do any of you guys know much about the knock sensors on the E46? Iím getting code 27E2 and 27E3 on mine. Iíve ran DIS on it and it does a few tests, one of which it has you monitor the voltage of sensor 1 & 2 at 2500 RPM. Iím not seeing any change in the voltages of either sensor, in fact they both remain at 0 volts during the test regardless of engine RPM. Given that, Iím think the most likely cause is a problem with the wiring to sensors. From what Iíve found, it looks like both sensors are feed from the DME on the same cable. Anyone know where the cable and the connector is located? I hate to pull the intake if unnecessarily.

It could also be the sensors I suppose, but for them both to go bad at once seems unlikely.

I also noticed a warranty defect code in DIS as I was poking around. The defect code was _12140815, but Iím not that familiar with DIS and have no idea what that means.
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old 06-12-2019, 03:48 AM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
I got scope out and had a look around underneath the intake. I found the cable going to the knock sensors to be completely severed, all 4 wires. I originally thought the cable got burned into but I'm not sure. It seems odd that all 4 wires were cut completely into and if you look close you can see that there are few strands that are longer than others like it was ripped out. I don't know what could have ripped it out though, very strange.

Anyway, it looks it will be a pain to repair. It's cut just on the harness side of the connector. Is the individual wire going into the wiring box under the intake replaceable? If not, maybe I can find another harness somewhere and splice that wire and connector into my existing harness. Seems like I read somewhere those are special shielded wires though, so I don't know. They are twisted into pairs. Anyone have any suggestions?
Attached Thumbnails
Click image for larger version

Name:	IMG_4193.JPG
Views:	21
Size:	117.3 KB
ID:	854691   Click image for larger version

Name:	IMG_4195.JPG
Views:	22
Size:	99.3 KB
ID:	854693  
Reply With Quote
  #3  
Old 06-12-2019, 07:48 AM
smolck's Avatar
smolck smolck is offline
ROLL TIDE!
Location: Birmingham, AL
 
Join Date: Jul 2007
Posts: 23,533
Mein Auto: 2003 330ci (5 speed)
Never seen that before. I am sure you could trace the wires back to the DME and re-pin them, but what a pain. Id try and splice them with new sensors and call it good. Sucks that if that doesn't work you have to take the intake BACK off though.
__________________
Check out my YouTube Channel for DIY's and other fun stuff HERE
Quote:
Originally Posted by Fast Bob View Post
now, go burn your Man Card, and buy yourself a Camry....
Reply With Quote
Sponsored Links
Advertisement
 
  #4  
Old 06-12-2019, 08:56 AM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
Thanks for reply. I was just in your neck of the woods this morning. Traffic on I20 on the East side is bad with all of the construction.

Anyway, new sensors aren't going to help, assuming the existing are still good. The wires are broke between the sensor connector and the little harness distribution box that sits under the intake. What I'm wandering is if that box can be taken apart, so just that cable can be replaced.

If not, I may be able to splice the cable but from what I've read the wires are shielded, which will complicate splicing them.

Last edited by Dahammer; 06-12-2019 at 09:05 AM.
Reply With Quote
  #5  
Old 06-13-2019, 06:47 AM
marcozandrini marcozandrini is offline
Officially Welcomed to the 'Fest
Location: Virginia
 
Join Date: Feb 2014
Posts: 4,923
Mein Auto: 2018 M240i
If your picture is correct the wires are not shielded.
Reply With Quote
  #6  
Old 06-13-2019, 08:00 AM
Tekken24/7 Tekken24/7 is offline
Registered User
 
Join Date: Jun 2019
Posts: 20
Mein Auto:
The wires are actuallyshielded. They aren't just bare wire. Splicing will not be a good idea due to the type of sensor. They are made to listen for knock from the engine. But it's your car. Make it work
Reply With Quote
  #7  
Old 06-13-2019, 10:17 AM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
Quote:
Originally Posted by Tekken24/7 View Post
The wires are actuallyshielded. They aren't just bare wire. Splicing will not be a good idea due to the type of sensor. They are made to listen for knock from the engine. But it's your car. Make it work
Do you know how they are shielded? Or where the shielding is located, like a braided sheaving around all 4 wires or something? Or is the shielding embedded in the PVC surrounding each wire or something? Because as marcozandrin suggested above, the pictures don't reveal the shielding. I have not taken it apart yet to get a close look at it though.

Do you have a suggestion on how to fix it properly?

I want to fix it right, as I don't want problems from it down the road. Having said that, I hate to have to replace the whole harness, if there is another way that will work fine. That's why I asked about removing just the damaged knock sensor cable from the junction box underneath the intake. From pictures I see of that box online, it appears it has a cover that snaps off, but I'm not sure what's inside it or whether or not the individual cables within it are replaceable or not. I know whole assembly from the E-box out can be replaced, but I really hate to do that if it's not necessary.

The Bentley manual shows that PIN 48 on the 52 pin ECM connector is the knock sensor ground, but I have not traced it yet. Anyone have a schematic they could share?
Reply With Quote
  #8  
Old 06-13-2019, 11:33 AM
Tekken24/7 Tekken24/7 is offline
Registered User
 
Join Date: Jun 2019
Posts: 20
Mein Auto:
Getting a better look at he that photo it look more so like it is severed where it connects. To my understanding purchasing a new sensor will fix that right up
Attached Thumbnails
Click image for larger version

Name:	38C53B89-1FDC-46AB-96D2-0B8D1B4847AA_1560450826450.jpeg
Views:	15
Size:	53.9 KB
ID:	854773  
Reply With Quote
  #9  
Old 06-13-2019, 03:48 PM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
Quote:
Originally Posted by Tekken24/7 View Post
Getting a better look at he that photo it look more so like it is severed where it connects. To my understanding purchasing a new sensor will fix that right up
Unfortunately it's the other end of the connector that is severed. The harness portion of the cable that connects to the wiring box underneath the intake. I wish it was on the sensor side, that would be easier to fix.
Reply With Quote
  #10  
Old 06-14-2019, 12:08 PM
Tekken24/7 Tekken24/7 is offline
Registered User
 
Join Date: Jun 2019
Posts: 20
Mein Auto:
Quote:
Originally Posted by Dahammer View Post
Quote:
Originally Posted by Tekken24/7 View Post
Getting a better look at he that photo it look more so like it is severed where it connects. To my understanding purchasing a new sensor will fix that right up
Unfortunately it's the other end of the connector that is severed. The harness portion of the cable that connects to the wiring box underneath the intake. I wish it was on the sensor side, that would be easier to fix.
Does it possibly have enough slack to just clean and pin the ends where the break is
Reply With Quote
  #11  
Old 06-14-2019, 01:36 PM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
Quote:
Originally Posted by Tekken24/7 View Post
Does it possibly have enough slack to just clean and pin the ends where the break is
Maybe, I'm not sure. I've get torn down and see what I'm dealing with. Hope to get it in the garage and start on it in the next few days.
Reply With Quote
  #12  
Old 06-24-2019, 07:57 PM
Dahammer Dahammer is online now
Officially Welcomed to the 'Fest
Location: MS
 
Join Date: Feb 2010
Posts: 134
Mein Auto: 2003 325i
I got the intake off yesterday for a closer look. The knock sensor cable is not damaged at all as best I can tell. But the all 4 wires in the cable that comes out of the wiring distribution box under the intake and connects to the knock sensor cable are severed right before they enter the connector.

There are 2 twisted pairs of wires, 4 wires total, in the wire loom. I snipped a little of the wire off and disassembled it. There is not any shielding (foil or braid) in the wires as best I can tell. There is a tiny slither of some type fiber that runs alongside the stranded wire underneath the outer PVC coating of each wire. I'm not sure what that is, but I'm guessing it just adds strength maybe? I ohm'ed the connector pins out and they connect directly to the broken stranded wires, just as it appears. So I'm left scratching my head because most everything I've read suggests the wires should be shielded all of the way from the ECM. Does anyone know if that is something that was changed? I know there were at least 2 different engine wiring harnesses on the E46s. All of the harnesses I've found thus far are $175+ ($375 a brand new one), which I hate to spend if I can just solder it back together and be done.

Beyond the wiring issue, I'm also wandering if the sensors themselves are likely damaged from being shorted out when the wires were severed (I'm thinking they were burned into but I'm not certain since I really can't envision how that happened). I connected a multimeter to the sensors and they appear to be an open circuit with 0 resistance. I read elsewhere there should be some resistance, but I can't find a spec for these specific sensors. But again I hate to replace perfectly good parts.

I'm tempted to replace the sensors, solder the connector back on the harness and put it back together. It's been over 100k since the CCV system was replaced, so I intend to do that too while the intake is off. Worse case is I have to take it back apart, I suppose.

Thoughts?
Reply With Quote
Reply

See More Related BMW Stories


Forum Navigation
Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 3 Series & 4 Series > E46 (1999 - 2006)
Today's Posts Search
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



Forum Jump


All times are GMT -7. The time now is 10:50 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
© 2001- VerticalScope Inc. All rights reserved.