AEM Series 2 Plug Play EMS 306821 User Manual

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Installation Instructions for: 
EMS P/N 30-6820 
2004 Subaru WRX STI (USDM 2.5L turbo) 
 
and 
 
EMS P/N 30-6821 
2005-2006 Subaru WRX STI (USDM 2.5L turbo) 
 
 
 
WARNING: 
! 
This installation is not for the tuning novice nor the PC illiterate! 
Use this system with EXTREME caution! The AEM EMS System 
allows for total flexibility in engine tuning. Misuse of this 
product can destroy your engine! If you are not well versed in 
engine dynamics and the tuning of management systems or...

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Thank you for purchasing an AEM Engine Management System.  
 
The AEM Engine Management System (EMS) is the result of extensive development on a 
wide variety of cars. Each system is engineered for each particular application. The AEM 
EMS differs from all others in several ways. The EMS is a stand alone system, which 
completely replaces the factory ECU and features unique Plug and Play Technology, which 
means that each system is configured especially for your make and model of car...

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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)...

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Variable Valve Control (VVC) 
The Variable Valve Control table in the EMS can be used to control the STI’s AVCS system, 
which is used to change the airflow characteristics of the engine by advancing the timing of 
the intake camshafts. The AVCS outputs (pin A28-A29, Injector 9-10 outputs on the EMS) 
advance the phase angle of the intake camshafts; this will have effects similar to moving an 
adjustable intake cam gear. This is controlled by the VVC 1 (RH camshaft) and VVC 1B (LH...

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EMS DC Stepper Motor control (Subaru Tumble Generator Valves) 
There are two sets of Tumble Generator Valves (TGV) found on the intake manifold of the 
STI. Each set of valves is driven by a DC stepper motor and has a 0-5V feedback signal to 
monitor valve position. The Motor 1 and Motor 2 Target tables are used to set the position of 
the valves; valve position can be controlled based on various parameters such as throttle 
position, vehicle speed, engine RPM, or engine load. The...

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AEM Electronic Throttle Control System (ETC)  
The 30-6820 EMS incorporates an ETC system which controls the OEM electronic throttle body.  All 
components of this system, unmodified and as delivered from the manufacturer, are required for optimum and 
safe functionality of this system.  These components include, but are not limited to, wiring, ETC relay, 
accelerator pedal assembly, and throttle body. 
 
The EMS ETC control system incorporates multiple failsafe strategies such that in the...

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Electronic Throttle Control System Calibration Procedure 
The 30-6820 / 30-6821 EMS, as delivered, requires a specific calibration procedure to be performed prior to 
use.  Before beginning this procedure, please be familiar with the location and function of the CRUISE and 
SET/COAST buttons on the Cruise Control Steering Column Stalk as depicted in Figure 2.  Also be aware of 
the (green) CRUISE and SET indicator lights on the dashboard, Figure 3.  This procedure should be 
repeated any...

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2. EMS Calibration 
a. Connect to the EMS using AEMTuner.  
b. Edit the Idle% vs. Target table, such that all cells are set to zero (0) percent. 
c. Edit A/C Idle Load Comp and/or Idle Extra > Set Throttle Range Wizard in the AEMTuner software and complete the procedure.  
f. Restore the above Options to their original values to ensure proper idle control functionality. 
 
 
 
 
 
 
Re-calibrating the Electronic Throttle Control System (ETC) Calibration  
Once the ETC system calibration...

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EMS Idle Control Calibration 
The ETC idle control can be configured and calibrated via the AEMTuner software similarly to more traditional 
systems that use an idle air bypass valve.  There are a few calibration options that are set specifically to allow 
proper ETC idle control and must not be changed from the values set forth in the 30-1820 startup calibration.  
The options listed below must remain set as depicted for predictable ETC idle control.  The other options that 
are not...

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2. Operational Fault – When the system detects a fault during normal operation (e.g. driving, 
idling, etc), the indicator lights will repeatedly flash in an alternating pattern to alert the user of 
this fault until the ignition key is turned off.  Note that the ETC system will not be functional and 
the EMS may disable engine operation during this mode depending on the severity of the fault.   
 
Once the ignition has been turned off and then on again the indicator...