ABS and SRS: Notes

WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Diagnostics Communication Diagram (ABS And SRS)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Diagnostics Circuit Diagram (ABS And SRS)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

ABS and SRS are each connected to the data link connector pin 8 through a communications lead.

The diagnostics instrument communicates digitally and serially with the selected system. With digital communication the difference in voltage between the lead and ground has only two values, in this case about 0 V and B+. The information is coded so that different combinations of 0 V and B+ pulses have different meanings, such as whether the SRS or ABS is to be called.

Serial means that the information is sent in "packets" one after the other in rapid succession.

The TC/ABS control module on cars with Traction Control is connected to the bus but diagnostic communication takes place via the K line.