On-Board Diagnostic System

COMMUNICATION
Isat Scan Tool
The Trionic ECM communicates with an Intelligent SAab Tester (ISAT) scan tool via pin 33. The communication is two-directional and thus involves both input and output signals.

The ISAT scan tool can communicate with Trionic with the ignition switched ON and the engine running, but also for 15 minutes after the engine has been switched OFF. Obviously no functions requiring a +15 or +54 supply can then be activated.

When the engine is running, the diagnostics function has low priority in the Trionic ECM. Trionic therefore breaks off contact with the ISAT at high engine speeds.

The ISAT display shows "NO CONTACT", and Trionic has to be reselected if communication is wanted.

The fault memory of the Trionic ECM is erased if the ECM is de-energized.

Flashing codes
In order to comply with current legal requirements in the US market (OBD I), it must be possible to read off emission-related faults via flashing codes on the malfunction indicator lamp (CHECK ENGINE).