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Knock Sensor Replacement
 
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Pelican Technical Article:

Knock Sensor Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$300

Tools:

Set of sockets (10mm, 13mm), flathead screwdriver, T27 Torx driver, torque wrench

Applicable Models:

BMW X5 (2000-06)

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

Knock sensors are piezoelectric knock sensors. The knock sensor is constructed of a crystal that when pressure or vibrations are sensed, electricity is created. Via software and sensor design, this crystal can be used to monitor a gasoline engine for noise or knock. The software in the DME is programmed to the frequency of ignition knock or detonation to prevent erroneous readings, as the sensor will react and create voltage with mechanical noises as well.

E53 models with an M62 8-cylinder engine utilize four sensors to monitor engine knock. The knock sensors are mounted to the engine block, below the intake manifold in the engine valley. 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. 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 E53. The quick test will be at the end of the tech article.

Knock sensors for each bank are paired and have to be replaced together. I would suggest replacing all four at a time due to the labor just accessing them.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Disconnect the negative (-) battery cable. See our tech article on battery connection notes.

Remove the engine covers. See our tech article on removing the engine covers.

The knock sensors are located under the intake manifold, mounted to the crankcase.
Figure 1

The knock sensors are located under the intake manifold, mounted to the crankcase. There are four in total (red arrows), one mounted between each set of cylinders.

First we have to remove the intake air duct that runs from the throttle housing (yellow arrow) to the mass airflow sensor (green arrow).
Figure 2

First we have to remove the intake air duct that runs from the throttle housing (yellow arrow) to the mass airflow sensor (green arrow).

Working at the fresh air intake, remove the four plastic rivets (green arrows).
Figure 3

Working at the fresh air intake, remove the four plastic rivets (green arrows). Use a pair of pliers (inset) to remove the center rivet. Once all the center rivets have been removed, pull the duct up to detach it from the vehicle.

Then lift the duct up on the left side while detaching it from the duct (green arrow) on the right side.
Figure 4

Then lift the duct up on the left side while detaching it from the duct (green arrow) on the right side.

Working at the mass airflow sensor, loosen the hose clamp using a flathead screwdriver (green arrow).
Figure 5

Working at the mass airflow sensor, loosen the hose clamp using a flathead screwdriver (green arrow).

Working at the throttle housing duct, loosen the hose clamp using a flathead screwdriver (green arrow).
Figure 6

Working at the throttle housing duct, loosen the hose clamp using a flathead screwdriver (green arrow).

Next you will have to rotate the throttle-housing duct up toward the left side of the vehicle in the direction of the green arrow.
Figure 7

Next you will have to rotate the throttle-housing duct up toward the left side of the vehicle in the direction of the green arrow. This will detach it from the mass airflow sensor. Once detached from mass airflow sensor, pull the duct off the throttle housing. There are two small hoses you have to disconnect in the following step. Be careful not to damage them during this step.

Working at the bottom of the intake air duct, detach the plastic line by squeezing the release collar (green arrows) while pulling the line off the duct.
Figure 8

Working at the bottom of the intake air duct, detach the plastic line by squeezing the release collar (green arrows) while pulling the line off the duct. Then pull the vacuum hose (yellow arrow) straight off the duct to remove it.

When removing the duct, be sure not to misplace the rubber duct seal (green arrow).
Figure 9

When removing the duct, be sure not to misplace the rubber duct seal (green arrow). The seal will either stay inside the duct or remain attached to the throttle housing.

Working at the throttle housing, disconnect the electrical connector by squeezing the plastic release tabs (on top and bottom of connector) and pulling it off in the direction of the green arrow.
Figure 10

Working at the throttle housing, disconnect the electrical connector by squeezing the plastic release tabs (on top and bottom of connector) and pulling it off in the direction of the green arrow. Remove the four 10mm throttle-housing fasteners (green arrows). Use a 1/4-inch ratchet with a two-inch extension to clear the surrounding components.

Remove the intake manifold.
Figure 11

Remove the intake manifold. See our tech article on intake manifold removing. Be careful not to break the crankcase breather nipple (red arrows) located at the left rear of the intake manifold. Once the intake is removed, cover the intake ports (green arrows) with tape (yellow arrows).

Now it's time to replace the knock sensors.
Figure 12

Now it's time to replace the knock sensors. Working at the knock sensors, remove the 13mm knock sensor fastener (remember to throw the fasteners away and do not reuse them) (red arrows). The left side is shown.

Then remove the knock sensor from your engine.
Figure 13

Then remove the knock sensor from your engine.

Be sure the mounting surface (red arrow) is clean.
Figure 14

Be sure the mounting surface (red arrow) is clean. Then install the new knock sensors finger tight. Then torque the knock sensor fasteners 20 Nm. Reassemble engine and check DME for fault codes.

This photo shows the right side sensors (red arrows).
Figure 15

This photo shows the right side sensors (red arrows). The procedure is the same as the left.

Testing knock sensors: 
Testing knock sensors To test the sensors, you will have to remove the engine covers as shown above.
Figure 16

Testing knock sensors: To test the sensors, you will have to remove the engine covers as shown above. Once removed, you will backprobe the connector with the ignition ON. Locate the knock sensor electrical connectors, yellow arrow points to bank 1, red arrow points to bank 2. Each connector houses two sensors. There are four wires at the connector, 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 the engine and check the DME for fault codes.


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Comments and Suggestions:
Crunch Comments: Do you sell the knock sensor fasteners? I'm not finding them.
October 10, 2016
  Followup from the Pelican Staff: Yes. 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
 
bimmerman Comments: Is left sensor different then right sensor.?
I changed mien and now the connectors don't fit properly and I must twist them in order to connect them. I really don't want to remove manifold again.

Thanks
April 28, 2016
  Followup from the Pelican Staff: Yes, only sue to the integrated harness, they can be installed only in one orientation. - Nick at Pelican Parts  
bimmerman Comments: Is left sensor def rent then right sensor.?
I changed mien and now the connectors don't fit properly and I must twist them in order to connect them. I really don't want to remove manifold again.
April 28, 2016
  Followup from the Pelican Staff: Yes, only sue to the integrated harness, they can be installed only in one orientation. - Nick at Pelican Parts  

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Page last updated: Wed 12/7/2016 02:47:35 AM