In hydraulic brake models, the scan tool accesses the electronic brake control module (EBCM) through CKT 396 (BRN/WHT) or CKT 799 (TAN/WHT).

In air brake models, the scan tool accesses the EBCM through the following circuits:

These communication lines monitor the modules for diagnostic purposes and inspect for diagnostic trouble codes (DTCs). Circuit breaker 5 applies voltage at all times to the data link connector (DLC). Joint connector 1 permanently grounds the DLC.