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2000 BMW 540i ABS wheel speed sensor bad

Tiny
PHANTOMSYS
  • MEMBER
  • 2000 BMW 540I
  • V8
  • 2WD
  • AUTOMATIC
  • 16,200 MILES
I have had the ABS and traction control and the other sensor light for stability control came on one warm day then went out after a cold day then stayed on until a rainy day. It went away for the day. I get the P0500 code only my speed gauge works so does the computer speed and the cruise control. I tried to look at the diode test with home built test leads that fit the 2 pins but never get anything from all 4 sensors. I changed one rear with new and it fell apart took a few hours to remove all the plastic in the hole. I just don't understand how to test the sensor properly. DO I use the line with arrow for testing with my meter or OHMS set at 20m and if so what should be the right reading for each speed sensor? I'm not fixing the unit until I test each wheel speed sensor. I also see that there is a sensor under the drivers seat.
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Monday, June 1st, 2009 AT 7:52 AM

3 Replies

Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
The correct method involves observing the conditioned signals from the DSC control module to the instrument cluster and it requires equipment and software at the dealership level. The under seat unit is for the directional input to the DSC.
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Monday, June 1st, 2009 AT 8:56 AM
Tiny
PHANTOMSYS
  • MEMBER
  • 2 POSTS
I have my own pin probes just for the speed sensors so I need to know what to test for and the proper settings for my volt meter so I get it right.I'm sure it must have a bad reading if it's not working properly. I have been told to set the meter to the setting were it has an arrow pointing to a line. I should get a reading from that of 14.5 to 17.8 at most but when I tried that I got nothing on all sensors so that can't be right. Someone else said use OHM set to 20M and then test. I know there is a test as I can buy the tester so since I made my own probe leads can you tell me the setup to test if speed sensor is out of range?I don't want to buy the tester for $250. When I made one for almost nothing. I was also told if it was the ECU then it's from bad solder so when it's cold it works and when it's hot it stops working so I froze my unit overnight in an airtight bag and tried it no luck same 3 warning light came up. They did go away on a very rainy day so maybe a bad wire.
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Monday, June 1st, 2009 AT 9:28 AM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,601 POSTS
It seems as if we are not communicating. The sensors are passive diffusion and generate a voltage when the car moves and that voltage goes to a analog to digital converter in the DSC control module, that's why I said "conditioned signals". Often the fault for a faulty wheel speed sensor is not the sensor, it is the DSC control module. The conditioned wheel speed signals can be viewed on a GT-1 which is the device used at the dealer level and when the fault for a bad wheel speed sensor is logged, it still shows wheel speed at that wheel. What I have just described is the process for the diagnostics and possible repair of the DSC system.
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Monday, June 1st, 2009 AT 9:54 AM

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