Ok....it has been nearly a decade since I've messed with installing the C5 ABS system on a GTM. If memory serves, I've only done this when installing the C5 engine ECU. I'm currently working on a customer's car where we have replaced the C5 ECU with an aftermarket ECU/Fuel injection system. My question....can the C5 ABS module work to provide ABS if there is no CAN/BUS serial data link between the C5 ECU and the ABS module? Can the ABS module operate just off of the wheel sensor inputs, brake pressure sensor and brake switch input?