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Old 05-21-2009, 07:27 PM
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540iman 540iman is offline
resident, old fart
Location: N.W. Indiana
Join Date: Sep 2008
Posts: 1,870
Mein Auto: 2002 540i sport
Look guys, you all are speculating and associating completely unrelated stuff with the module and all that. Lets do this right and not just play musical parts. Borrow or buy a digital VOM (volt/ohm meter) from Menards. Make sure it has a diode check position. Ask the clerk if you are unsure of the diagram of a diode. You will check all four sensors at the Module. Very easy two wires to each sensor. With the meter in the diode position and checking the points I will tell you, you will get a reading of "open" or no display with the leads connected one way. You will then reverse the meter leads and you will get the opposite of whatever you got before. If you get a reading of 1.7 -1.8 volts you should get nothing (infinity) the other way. If you get infinity, reverse the leads and you should get 1.7 v-1.8v. The car should be completely off. You are reading the diode action in the sensor itself. If you get infinity with the leads both ways BINGO, you found the bad sensor. If all 4 sensors give open one way and a 1.7-1.8 volt drop the other way, the module is bad. Its that easy. Always better to rebuild your same module so you avoid having to have the dealer re-code a new module $100 for 5 min. work. ATE1234 on Ebay will rebuild your module for $105 and you get lifetime warranty and free return shipping. I will post the wires you want to check. When you remove the big connector at the module, look carefully and you will see the numbering scheme. The pins are so small you will insert paper clips into the correct terminals and then connect the meter leads to the paper clips.

rf= 15-16
lf= 12-28 These are the ABS module main connector pin numbers
rr= 30-31
lr= 13-29

If you find a bad sensor, remove the blue connector end of the speed sensor assm. Re-check the sensor there just like before there are two pins. put paper clips in being careful not to allow paper clips to touch one another. Test the sensor open/infinity in one direction and 1.78v in the other means the sensor is good and the wiring to the sensor or that blue connector connection is bad. Flush both sides with contain cleaner and reinstall. See if error is not clear. If you need more detail, please just ask. There are other things that can screw the system up like angle sensors and so forth, but the wheel speed/abs sensors by far are the more common (or the module). Try to re-build YOUR module. No recoding and even a new module will still be subject to heat failure just like your old one. A re-built will use bigger diodes and point-to-point wiring.

Last edited by 540iman; 05-21-2009 at 07:46 PM.
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