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BMW Knock Sensor Replacement
 
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Pelican Technical Article:

BMW Knock Sensor Replacement

Nick Czerula

Time:

4 hours4 hrs

Talent:

***

Tools:

Set of sockets (10mm, E12), flathead screwdriver, T27 Torx driver

Applicable Models:

BMW 325i/xi Sedan (2006)
BMW 328i xDrive Sedan (2009-11)
BMW 328i/xi Sedan (2007-11)
BMW 330i/xi Sedan (2006)
BMW 335i xDrive Sedan (2009-11)
BMW 335i/xi Sedan (2007-11)

Parts Required:

Knock sensors, knock sensor fasteners, intake manifold gasket and related fasteners

Hot Tip:

Work with a cool engine

Performance Gain:

Remedy knock sensor fault codes

Complementary Modification:

Replace crankcase breather while intake manifold is removed

E90 models utilize two sensors to monitor engine knock. The knock sensors are mounted to the engine block, below the intake manifold. The knock sensors usually fail setting a check engine light and a knock sensor fault code. When a knock sensor fails, the ignition timing on your engine may be held in a retarded position until the fault is remedied, therefore reducing engine power and the chance of detonation. The sensors are replaced in pairs and you have to replace the fasteners also. In this tech article I will go over how to test and replace the engine knock sensors on your BMW E90. The quick test will be at the end of the tech article.

This photo shows the location of both knock sensors.
Figure 1

This photo shows the location of both knock sensors. You can see them from above the intake manifold, looking down through the intake manifold runners. (green arrows) Disconnect negative (-) battery cable. See our tech article on Battery connection notes. Remove engine covers. See our tech article on removing engine covers. Next you have to remove the air filter housing and intake air ducts from your engine. Use the steps below that apply to your vehicle, then complete procedure with steps following the air filter housing and duct removing steps.

Models without turbo-charger:
Working at front of radiator support, remove two T20 Torx fasteners for the intake duct.
Figure 2

Working at front of radiator support, remove two T20 Torx fasteners for the intake duct. (green arrows)

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs on each side and pull duct off.
Figure 3

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs on each side and pull duct off.

Then, pull intake duct out of radiator support and remove from vehicle.
Figure 4

Then, pull intake duct out of radiator support and remove from vehicle. (green arrow)

Then loosen hose clamp (green arrow) and remove two 10mm air filter housing fasteners.
Figure 5

Then loosen hose clamp (green arrow) and remove two 10mm air filter housing fasteners. (yellow arrows)

Disconnect mass air flow sensor electrical connector by releasing tab with small flathead screwdriver and pulling connector out of sensor.
Figure 6

Disconnect mass air flow sensor electrical connector by releasing tab with small flathead screwdriver and pulling connector out of sensor. (green arrow)

Remove air filter housing from vehicle by lifting up and disconnecting duct from mass air flow sensor.
Figure 7

Remove air filter housing from vehicle by lifting up and disconnecting duct from mass air flow sensor.

Next you will have to remove the power steering reservoir from its mounting bracket.
Figure 8

Next you will have to remove the power steering reservoir from its mounting bracket. You do not have to disconnect the hoses. Remove two 10mm mounting fasteners. (green arrows) Then remove two sliver washers from power steering reservoir grommets. Be careful not to lose the washers.

Working next to power steering reservoir, unclip vacuum hose clip by unclipping and opening.
Figure 9

Working next to power steering reservoir, unclip vacuum hose clip by unclipping and opening. (green arrow)

Remove power steering reservoir (green arrow) from mounting bracket and guide under vacuum hose (yellow arrow) and lay aside.
Figure 10

Remove power steering reservoir (green arrow) from mounting bracket and guide under vacuum hose (yellow arrow) and lay aside.

Working at throttle body intake air duct, pull off vacuum hose.
Figure 11

Working at throttle body intake air duct, pull off vacuum hose. (green arrow)

Working at throttle body, loosen intake air duct hose clamp (green arrow) using a flathead screwdriver.
Figure 12

Working at throttle body, loosen intake air duct hose clamp (green arrow) using a flathead screwdriver. You will have reach from the firewall side to access clamp with screwdriver. A shorter flathead screwdriver works best.

Pull air duct straight off throttle body.
Figure 13

Pull air duct straight off throttle body. (green arrow) Note installation position for easier reinstallation.

Models with turbo-charger:
Working at front of radiator support, remove two T20 Torx fasteners for the intake duct.
Figure 14

Working at front of radiator support, remove two T20 Torx fasteners for the intake duct. (green arrows)

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs (green arrow) on each side and pull duct off.
Figure 15

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs (green arrow) on each side and pull duct off. Then, pull intake duct out of radiator support and remove from vehicle.

Working at front of air filter housing, using a flathead screwdriver loosen air duct hose clamp.
Figure 16

Working at front of air filter housing, squeeze connector and pull disconnect vacuum hose, then pull vacuum hose out of mount. (green arrow)

Once hose clamp is loose, reach below upper radiator hose and slide hose (green arrow) off air filter housing.
Figure 17

Working at front of air filter housing, using a flathead screwdriver loosen air duct hose clamp. (green arrow) Then loosen boost pipe hose clamp (yellow arrow). Leave boost hose connected for now.

Working at rear of air filter housing, using a flathead screwdriver loosen air duct hose clamp.
Figure 18

Once hose clamp is loose, reach below upper radiator hose and slide hose (green arrow) off air filter housing.

Pull electrical cable up off mount.
Figure 19

Working at rear of air filter housing, using a flathead screwdriver loosen air duct hose clamp. (green arrow) Next you will have to detach electrical cables from intake air pipe. (yellow arrow)

Once the electrical cables are removed, you will have to pull the air filter up and out of the rubber mounting grommets.
Figure 20

Pull electrical cable up off mount. You may have to wiggle the rubber grommet side to side to get it to come off mount. Remove all three electrical cables.

Next you will have to unlock and disconnect the front boost recirculation hose.
Figure 21

Once the electrical cables are removed, you will have to pull the air filter up and out of the rubber mounting grommets. There are two in the back and one located in the center. What I like to do is pull the front side up first, then wiggle the air filter housing until it comes out of the rear mounts. There are no fasteners holding it, just the grommets, and over time they may become stiff and will not release easily. If that is the case use caution and pull up swiftly to release.

Next, pull hose up and off air pipe.
Figure 22

Next you will have to unlock and disconnect the front boost recirculation hose. There is a gray lock, rotate this lock counterclockwise about 45° to unlock it. This style hose lock and be hard to get off due to time and debris entering collar. If so, you can rotate it using channel locks, but be careful not to damage the hose or lock, they are made out of plastic.

Next you will have to unlock and disconnect the rear boost recirculation hose.
Figure 23

Next, pull hose up and off air pipe. It should slide off easily, if it does not, lock is not fully disengaged.

Working at the boost recirculation valves, remove the vacuum hose from each valve by pulling off.
Figure 24

Next you will have to unlock and disconnect the rear boost recirculation hose. There is a gray lock, rotate this lock counterclockwise about 45° to unlock it. This style hose lock and be hard to get off due to time and debris entering collar. If so, you can rotate it using channel locks, but be careful not to damage the hose or lock, they are made out of plastic. Next, pull hose up and off air pipe. It should slide off easily, if it does not, lock is not fully disengaged.

Working at the boost air pipe, remove T27 Torx fastener.
Figure 25

Working at the boost recirculation valves, remove the vacuum hose from each valve by pulling off. Be careful not to damage hose or valve when removing.

Working at throttle body, using a flathead screwdriver, remove intake air pipe locking clip.
Figure 26

Working at the boost air pipe, remove T27 Torx fastener. (green arrow)

Disconnect boost pipe from connection at radiator support, then gently wiggle pipe off throttle body.
Figure 27

Working at throttle body, using a flathead screwdriver, remove intake air pipe locking clip. (green arrow)

Now it's time to replace the knock sensors.
Figure 28

Disconnect boost pipe from connection at radiator support, then gently wiggle pipe off throttle body. Once pipe is clear of throttle body, remove from vehicle.

Replacing knock sensors:

Remove the intake manifold from your engine. See our tech article on intake manifold removing.

Locate the knock sensor electrical connector.
Figure 29

Now it's time to replace the knock sensors. Working at the knock sensors, remove the E12 knock sensor fastener (remember to throw the fasteners away and do not reuse them.. (green arrow) Then remove the knock sensor from your engine. Be sure the mounting surface is clean, then install new knock sensors finger tight. Then torque the knock sensor fasteners. 7 Nm (63 in-lb) once torqued, rotate fastener another 90° Reassemble engine and check DME for fault codes.

Testing knock sensors:

To test the sensors, you will have to remove the air filter housing and ducts as shown above. Once removed, you will backprobe the connector with the ignition ON.

There are four wires at the connector (green arrow), two for each sensor.
Figure 30

Locate the knock sensor electrical connector. (green arrow) It is mounted to the bottom of the electrical junction, under the throttle body. It should pull straight off bottom of junction.

There are four wires at the connector (green arrow), two for each sensor.
Figure 31

There are four wires at the connector (green arrow), two for each sensor. One is a ground, the other is a reference voltage used for circuit integrity. Here's the quick test, use a DVOM, connect the black lead to battery negative, then connect the positive lead to the sensor wires. One wire should read close to 0 volts, this is the sensor ground. The reference voltage wire should read around 2.5 volts, for a good sensor. A bad sensor will either short the reference voltage to ground, or not pull it down to 2.5, therefore giving a reading of about 5 volts. Reassemble engine and check DME for fault codes.

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Comments and Suggestions:
Jaz Comments: Hi Nick. I don't know which cylinders are misfiring but it seems that it is the timing at fault. Surely the knock sensor should have a reading on every cylinder? If there is no reading at all on 2 and 3 then could it be the knock sensor at fault?
November 27, 2016
  Followup from the Pelican Staff: To isolate the misfire, I would check spark, fuel and compression on all cylinders.

Misfire doesn't equal knock. They don;t always go hand in hand. - Nick at Pelican Parts
 
Jaz Comments: Hi. My 2006 320i msport auto is misfiring when accelerating fro m the lower rev range. Ecu errors say catalytic converter and minimum valve lift exceeded, however, it has already had a new catalytic converter and motronic valve fitted. The live readings shown by the knock sensor indicate that cylinders 2 and 3 have zero values. Is this normal or is the knock sensor faulty?
November 20, 2016
  Followup from the Pelican Staff: What cylinders are misfiring? Knock control may be off due to misfire. - Nick at Pelican Parts  
Jim Comments: "One wire should read close to volts"

Should this read as One wire should read close to "0" volts?
September 1, 2016
  Followup from the Pelican Staff: Thanks for the catching that. We appreciate it. I will have the article updated. - Nick at Pelican Parts  
New2bmws Comments: Does this website supply parts for a 2007 323i? I need to replace the knock sensor but it doesn't show my applicable model.
July 24, 2016
  Followup from the Pelican Staff: Pelican Parts can get them for you. Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
New2bmws Comments: I have a 2007 323i. First, how do I know if it's an e90, e92, etc...? Second, will my 323i use the same parts as the 328i? It's throwing a knock sensor code.
July 21, 2016
  Followup from the Pelican Staff: E90 sedan, E91 wagon, E92 coupe, E93 convertible.

Not all engines use the same parts, buy parts for your model only.

Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
lee68 Comments: what is the torque setting on a 2007 530xi knock sensor. its appearance is identical to your photo.
Thank you
July 7, 2016
  Followup from the Pelican Staff: I don’t have that info.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Dylan Comments: sir, there is a typo at the discription on Figure 31. What is the voltage? kindly amend. THanks.
March 15, 2016
  Followup from the Pelican Staff: The voltage specs are there. - Nick at Pelican Parts  
Cal Comments: Well it was Difficult to access the knock sensor for removal i had to take out the alternator to access the same ,it was not show in your description ? by the procedure shown by you it was not posssible to remove the knock sensor? it would be nice if you would add the same
December 8, 2015
  Followup from the Pelican Staff: Not difficult, but the intake manifold has to be removed. As stated in the article. - Nick at Pelican Parts  
Cal Comments: Thanks for the info it was very helpful
December 6, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
e92 Comments: hi Nick & thanks flr help. could you send me a link to the threat please ?
November 22, 2015
  Followup from the Pelican Staff: http://forums.pelicanparts.com/bmw-general-discussion/891864-hi-where-would-i-need-refer-nox-replacement-e92-2-0-petrol-error-p2205-nox-sensor-heater-control-circuit-open-bank-1-a.html - Nick at Pelican Parts  
e92 Comments: hi where would I need to refer to for a NOx replacement in e92 2.0 petrol? the error is P2205 nox sensor heater , control circuit open bank 1

would this erro refer to knox shown in pictures above or one next to exhaust system ? THANKS !
November 19, 2015
  Followup from the Pelican Staff: We don't have that sensor in the US, so I can;t offer any insight as I have no experience with it. I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
 
Brandon Comments: Good Afternoon, I threw a p1328 code on 07 e92 335i, which is the high input knock sensor, I understand there is a high and low input. Would I need to purchase two separate sensors? I noticed that an individual sensor connects at two locations. I wasn't sure if one sensor was sufficient for the high and low. Thanks!
July 9, 2015
  Followup from the Pelican Staff: If you have one knock sensor fault, replace them both. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
dips Comments: Hi, I have checked the codes with INPA and im getting errors
P122C, P121F and P122F. which sensor would this be?
I have a BMW 325I e92 N53 2009/
June 4, 2015
  Followup from the Pelican Staff: These codes usually indicate a faulty NOX sensor.

P122C NOx sensor (Bank 1) - Short circuit
P121F NOx sensor linear lambda signal circuit (Bank 1) - Short circuit
P122F NOx sensor binary lambda signal circuit (Bank 1) - Short circuit - Nick at Pelican Parts
 

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Page last updated: Sat 12/3/2016 02:23:34 AM