ABS Diagnostic Data

By Andy Keatley
January 2001

Please find to follow copy of letter to Brian Curry re: ABS diagnostics. Hope is of interest.

Dear Brian,

I found your information on ABS diagnostics via a link from a very good British BMW breakers site http://www.james-sherlock.co.uk/.

With your info along with Richard Paton's I have fixed my 16v RS's fault.

However I found readings for resistances into the modulators as below:

Computer connector pins:


6(-) to 9(+) 4.4K  
7(-) to 11(+) 4.4K
6(-) to 10(+) 1.9M  
7(-) to 12(+) 2.1M
9(-) to 10(+) 1.9M  
11(-) to 12(+) 2.1M

I suspect the readings depend upon how much current the meter used injects. Maybe there is an active device of some sort, probably a darlington power transistor to drive the coil in the unit because using the diode check function on my meter (Fluke85) I obtained the following readings:

Computer connector pins:

6(-) to 9(+) 1.79V  
7(-) to 11(+) 1.79V
6(-) to 10(+) 1.59V  
7(-) to 12(+) 1.59V
9(-) to 10(+) 1.49  
11(-) to 12(+) 1.50V

Hope this is of interest and thanks for your very useful information.

Regards Andy Keatley