AEM 30-6821 Series 2 Plug & Play EMS User Manual
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Read and understand these instructions BEFORE attempting to install this product.
Subaru 2004 / 2005-2006 Model Year Differences
Although there are very few differences between the 2004 and 2005-2006 models, the ECUs
are not interchangeable. The 30-1820 EMS must be used in a 2004 vehicle, and the 30-1821
EMS must be used in 2005-2006 vehicles. Consult the pinout chart for further information.
Peak and Hold Injector Drivers
Injectors 1-4 include Peak (4 amps) and Hold (1 amp) injector drivers. These drivers may be
used with peak and hold or saturated type injectors. The
vehicle’s wiring harness may
contain a resistor pack to prevent excessive current if low-impedance injectors were used
with the stock ECU. With the 30-6820 installed, users can elect to remove and bypass
injector resistors for more precise control of low-impedance injectors.
Please note that the injector response time will be different with and without injector resistors
installed. If a resistor pack has been removed and bypassed, please use the correct battery
offset wizard for your injectors. Most battery offset wizards will specify
they are intended for use without a resistor pack.
Fuel Pump Control
As supplied from Subaru, the OEM ECU interfaces with a fuel pump control unit (FPCU) to
control the speed, high or low, of the fuel pump based on load. The AEM EMS has the ability
to replicate this functionality; however it is configured in the Startup Calibration to run the fuel
pump at high speed at all times.
The EMS Output COIL8 (Pin B26 for 2004 models, pin B27 for 2005-2006 models) is used to
send a 5V signal instructing the OEM fuel pump ECU to energize the fuel pump. Configuring
User PW Out to use LS12 and, for example, User PW Analog In to MAP Volts will allow the
voltage sent to the fuel pump ECU to be varied in relation to MAP Volts/pressure. Increasing
the duty cycle of the LS12 output will decrease the speed of the fuel pump.
WARNING: Reducing the voltage sent to the fuel pump can affect fuel pump output (volume
and/or pressure). If you wish to decrease pump speed at light loads or low RPM, monitor
fuel pressure and air-fuel ratio very carefully to avoid engine damage!
WARNING: Do not use pin B26/B27 to control a fuel pump relay directly, it must be
connected to the OEM fuel pump control unit only. If an aftermarket fuel pump relay will be
installed, wire it to be controlled using a spare low side output (for instance, LS2 is available
on pin A13). Be sure to configure the output to use the Fuel Pump function using
Tools>>Configure Outputs.