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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 01-21-2013, 06:32 PM
wolfbone71 wolfbone71 is offline
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knock sensor ohms

Is there any way to test the resistance on a knock sensor? I want to make sure they are faulty before I replace.
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  #2  
Old 01-21-2013, 08:06 PM
JimLev JimLev is offline
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Are they giving you any codes, if not they should be good.
They are piezoelectric devices, not sure you can get an ohm reading from them.
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Old 01-21-2013, 08:59 PM
geargrinder geargrinder is offline
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Quote:
Originally Posted by JimLev View Post
Are they giving you any codes, if not they should be good.
They are piezoelectric devices, not sure you can get an ohm reading from them.
Correct but they need to be torqued very specifically. Sometimes you can retorque them and theyll work fine. I like to remove and clean the mounting area, then retorque. Never done an E39 but its worked on other cars...
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Old 01-22-2013, 04:57 AM
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bluebee bluebee is offline
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Dunno if it adds any value, but I typed /knock sensor F3 in the bestlinks and this came up which may be of some help:
- How to better understand the piezoelectric knock sensor operation (1)
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Originally Posted by Flug540 View Post
I finished rebuilding my sensors over the weekend. Wasn't too bad, the first one took the longest time while I was trying to figure out the best technique. Below are some photos of the process and what they look like now. On the first two photos you can see what happens to the original internal insulation when you pull the outer shell. Resistance on all sensors actually gone up slightly, now it's about 4.98 MOhm, which I think shows that the original insulation already was beginning to conduct.

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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need

Last edited by bluebee; 01-22-2013 at 05:00 AM.
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Old 01-22-2013, 07:52 AM
geargrinder geargrinder is offline
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Originally Posted by bluebee View Post
Dunno if it adds any value, but I typed /knock sensor F3 in the bestlinks and this came up which may be of some help:
Cool post. I've never seen that bad insulation deterioration that's for sure! Interesting that the Bosch knock sensors look exactly the same as every other European car I've ever seen one on... I wonder if they are all identical just with different end connectors.
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  #6  
Old 01-22-2013, 12:29 PM
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bluebee bluebee is offline
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Mein Auto: 02 BMW 525i M54 auto 130K
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Originally Posted by geargrinder View Post
I wonder if they are all identical just with different end connectors.
I wonder also.

What would be nice, if someone gets a chance, is to snap a photo of the knock sensors in situ, on the engine, so that I can post it to this engine thread:
- Getting to know your M54 engine, a photo & identification guide to every visible part in the engine bay (1)
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See also: E39 Bestlinks & How to easily find what you need
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