ABS Diagnosis

Customer complaining of noise and brake judder, booked into a local garage for pads and discs.
These were fitted and the fault remained!
The garage checked for codes but as the ABS light was not illuminated they were not surprised to find a clean bill of health. No codes found.
I was asked to check the braking system and report my findings.
A quick test drive proved the ABS to be operating, but not when you expected.
In cases like this I like to remove the ABS fuse to disable the system, then perform a road test. This careful road test, remembering the ABS will not operate can prove if it is an ABS control or operating fault, or a mechanical fault in the braking system.
In this case the car now performed faultlessly. Proving an ABS fault.
But without fault codes how can it be diagnosed quickly?
Start with a visual check, and sure enough the reason was clear to see a cracked reluctor ring.
Not easy to spot, but easy to see with the scope.