AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 18)

Page 18 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
Noise can be caused by the electric motor in a fuel pump, which if connected directly to the
ECU, may feed back into the circuit board ground plane. In the case of a fuel pump, the typical
amperage required to run the pump is 10A or more depending on its size. The driver in the
ECU that sends the command to run the fuel pump is only capable of supplying 1.5A, and
clearly this type of load on the driver would cause it to burn out. There are drivers that can
handle larger currents but cost, size, heat dissipation, and noise problems prevent their use.

Typical relays in use today are capable of carrying 40A. A relay has an electromagnet
inside it that is used as a switch. This electromagnet, or switch, is used to position a
contact within the relay that is capable of carrying high current. There are typically four
or five terminals on the base of a relay. These terminals can be wired in several ways to
achieve different results. Refer to the EMS-4 System Schematic for common wiring
schemes used with relays.
Installation with Full Harness, P/N 30-3905-96
For the following section, please refer to the EMS-4 System Diagram for more
information. It shows a schematic representation of a properly designed system using
the fully populated harness.
NOTE: The columns in the connection tables below labeled “WIRE” refer to the wire
gauge recommended for the harness.
USB Connector
USB Connector