D-Jetronic - The units

When the ignition is switched on, the control unit receives the operating voltage directly from the battery via the main relay. To protect the D-Jetronic system, this relay is protected by a diode connected in series with the supply voltage.

If, for example, the positive and negative terminals are inadvertently reversed when connecting the battery, no current will flow that could destroy electronic components. To ensure that the main relay cannot be confused with the other relays, the housing is marked with a blue colour dot.