There is no diagnostic port on the Type C ABS ECU, which is the one you have. A special cable and test unit is needed to test the ECU which no one has. I can send you a copy of the manual (PM me your email address) which shows you how to do some diagnostics with a switch (not installed by WRV). My insurer would not pay for a new ECU without proof and I would have been out $1400 if that proved not to be the problem. I gave up, removed the ABS bulb and have never been bothered since.
FWIW the ECU is in front of your left foot and the side panel has to be cut back to remove it. The test connector is behind the cover below the transmission selector.
John and Mary Knight
2015 Ventana 4311, 2015 Cadillac SRX