Ignition discharge module: Diagnostics: Overview

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.

If there is an open circuit in the power supply to the ignition discharge module, the voltage on all the trigger leads will be 0V and diagnostic trouble code P1310 will be generated.
If there is an open circuit on an individual trigger lead, diagnostic trouble codes will not be generated.