Diesel engine control module and DAH: 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 (Diesel Engine Control Module And DAH - 1 Of 2)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Diagnostics Communication Diagram (Diesel Engine Control Module And DAH - 2 Of 2)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Diesel engine control module and DAH are each connected to a communication lead to data link connector pin 7.

The diagnostic tool communicates digitally and serially with the selected system. Digitally means that the voltage difference 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, like which system is to be called.

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