Control module power supply: Diagnosis

If no current from the +30 circuit is present, the display will not be active and diagnostic communication will not be possible.

If no current from the +15 circuit is present, the display will not be active but can be turned on via the bus by switching on the radio, for example. Diagnostic communication will be possible with limited functions if the ignition key is turned to ON.

The SID will not generate a diagnostic trouble code if no current is present from either the +30 or +15 circuits.