Thanks for the help guys, you were right, both rings had snapped, both were replaced but it didn't completeley cure it. Scoped the abs sensors and found o\s\r sensor very low amplitude, customer has extended warranty so we are waiting for an engineer to inspect before i can carry on the repair. I thought these might have been the problem with the low resistance of 1k. i should have checked this first, although i would have still missed the broken rings, the ecu never logged a fault code for this sensor though. Chris