AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 17)

Page 17 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
The routing of the wire loom is critical to EFI system performance and safety. The following
safety considerations should be made when installing the wire loom:

Heat protection: the loom should be placed away from or insulated from sources of heat.
The obvious item(s) that should be avoided are the exhaust manifolds, EGR delivery
tubes, and turbochargers. If it is absolutely necessary to route a wire in close proximity
to any of these items, then a suitable insulator must be used.

Noise suppression: do not route wires near the HT leads. For coil- on-plug ignition
systems this is not as critical.

Moving component protection: route wires away from moving components such as fans,
the blower belt, or the throttle linkage. Also, make sure the wires are not under any
strain when the engine is at full deflection on the motor mounts (we have seen map
sensor wires disconnect while under full acceleration because the motor mounts were
bad).

Never have the wires in exposed bundles throughout the engine compartment. A
professional harness has shrink tube over it to resist abrasion and chemical damage to
the wire loom.
Grounding
The ECU must have an electrically secure ground connection, which means that the battery
negative must be properly grounded to the chassis AND engine. The ground wire, whether it is
from the battery or to the chassis and engine, must have perfect electrical conductivity. This
means that there must not be any paint or rust under the wire terminal. Make sure that when
you install the ground wire there is bare metal exposed where the wire contacts the vehicle
component. To prevent rust build up, we recommend applying a protective layer of dielectric
grease, such as Standard Ignition SL-4, to the bare metal surface. The ground wire must be at
least the same gauge as the power lead to the ECU. We also recommend that the ground wire
be as short as possible.
Power Requirements of the AEM EMS
The AEM EMS requires a minimum supply voltage of 10V or greater to run. We recommend
that the ECU be supplied with 13.8V nominal operating voltage. Ensure that the vehicle‟s
charging system is in perfect operating condition prior to installing the AEM EMS.
Use of Relays to Control Ancillary Devices
Relays are remote switching devices that are used to isolate a device from the ECU‟s circuitry to
reduce noise and power constraints on the ECU. Typical devices that are powered by a relay
are:

Fuel Pump

Variable Valve Control

Oxygen Sensor Heater

ECU power

Nitrous Oxide solenoids