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 are 
not PC literate, please do not attempt the installation. Refer the 
installation to a AEM trained tuning shop or call 800-423-0046 
for technical assistance. You should also visit the AEM EMS 
Tech Forum at http://www.aempower.com 
 
NOTE: AEM holds no responsibility for any engine damage that 
results from the misuse of this product! 
This product is legal in California for racing vehicles only and should never be used 
on public highways. 
 
Vehicle fitment Series I EMS Series II EMS 
2004 Subaru WRX STI  30-1820 30-6820 
2005-2006 Subaru WRX STI 30-1821 30-6821 
    2011 Advanced Engine Management, Inc. ADVANCED ENGINE MANAGEMENT INC. 2205 126th Street Unit A    Hawthorne, CA. 90250 Phone: (310) 484-2322 Fax: (310) 484-0152 http://www.aemelectronics.com Instruction Part Number: 10-6820  
						

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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 without any 
jumper harnesses. There is no need to modify your factory wiring harness and in most cases 
your car may be returned to stock in a matter of minutes.  
 
For stock and slightly modified vehicles, the supplied startup calibrations are configured to 
work with OEM sensors, providing a solid starting point for beginner tuning. For more heavily 
modified cars, the EMS can be reconfigured to utilize aftermarket sensors and has many 
spare inputs and outputs allowing the elimination of add-on rev-limiters, boost controllers, 
nitrous controllers, fuel computers, etc. It also includes a configurable onboard 1MB data 
logger that can record any 16 EMS parameters at up to 250 samples per second. Every 
EMS comes with all functions installed and activated; there is no need to purchase options or 
upgrades to unlock the full potential of your unit. 
 
The installation of the AEM EMS on the supported vehicles uses the stock sensors and 
actuators. After installing the AEMTuner software, the startup calibration will be saved to the 
following folder on your PC:  
C:\Program Files\AEM\AEMTuner\Calibrations\AEM Updates\Subaru\  
Multiple calibrations may be supplied for each EMS; additional details of the test vehicle 
used to generate each calibration can be found in the Calibration Notes section for that file.  
 
Please visit the AEM Performance Electronics Forum at http://www.aemelectronics.com and 
register. We always post the most current strategy release, PC Software and startup 
calibrations online. On the forum, you can find and share many helpful hints/tips to make 
your EMS perform its best.  
 
 
TUNING NOTES AND WARNING:  
While the supplied startup calibration may be a good starting point and can save 
considerable time and money, it will not replace the need to tune the EMS for your specific 
application. AEM startup calibrations are not intended to be driven aggressively before 
tuning. We strongly recommend that every EMS be tuned by someone who is already 
familiar with the AEM software and has successfully tuned vehicles using an AEM EMS. 
Most people make mistakes as part of the learning process; be warned that using your 
vehicle as a learning platform can damage your engine, your vehicle, and your EMS. 
  
						

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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    if 
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.  
						

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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 
camshaft) outputs; VVC position is monitored using the T2 and T3 inputs for independent 
closed-loop feedback. The VVC settings can be adjusted in the VVC tab (which may be 
hidden in the default AEM workspace).  
 
This system is active on this EMS when used with the provided startup calibrations and can 
be adjusted through the use of the ‘VVC 1 Target’ map. Adjustments to the intake cam timing 
are made by changing the values in the ‘VVC 1 Target’ map per Engine RPM and Engine 
Load. The values in the ‘VVC 1 Target’ map can vary from 0 degrees for zero intake cam 
advance to 50 degrees for full intake cam advance.  The channels ‘VVC 1 Advance’ and 
‘VVC 1B Advance’ show the measured position of the camshafts.   
 
 
  
WARNING: Improper use of the Variable Valve Control (VVC) in the AEMTuner software can 
lead to engine damage!  
  
Be very careful when building or tuning unknown engine combinations or using aftermarket 
pistons or valve train components. OEM engines and valve trains are not designed or 
manufactured to allow valve to piston interference at certain cam angles. AEM will not be 
responsible for engine damage resulting from improper use of the VVC function on engines 
with valve trains designed to allow mechanical interference. 
 
 
 
Please note that some Subaru camshaft sensors will send ‘false signals’ under some 
conditions (often light load and low RPM). This can be observed with an oscilloscope or 
high-speed datalogger, and occurs with the stock ECU as well. These false signals will not 
cause engine misfires with the Series 2 EMS, but will sometimes be reflected as quick jumps 
in the measured ‘VVC 1 Advance’ channels.  
  
						

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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 channels “ADCR11” and 
“ADCR14” display the current position of the valves. When these parameters are near 0 
Volts, the valves are open and will allow maximum air flow. When these parameters are near 
5 Volts, the valves are closed creating turbulence in the intake stream and restricting air flow. 
The valves are always open in the AEM-supplied startup calibrations.  
 
WARNING: the EMS can be configured to control the left and right bank independently. The 
engine will run very poorly if one set of TGVs is fully open while the other set is fully closed, 
so please be sure that the Motor 1 and Motor 2 Target tables are both the same. 
 
 
Subaru MAF sensor, Intake Air Temp sensor 
The MAF (mass air flow) sensor can be removed to help decrease intake air restriction as 
the base map uses the factory MAP sensor to determine engine load. Please be aware that 
the IAT (intake air temperature) sensor is integrated into the factory MAF sensor. If the 
factory MAF / IAT sensor is removed, you may wish to install an AEM IAT Sensor Kit (P/N 
30-2010), which includes a sensor, wire connector, and aluminum weld-in bung. While the 
factory MAF sensor locates the IAT sensor upstream of the turbocharger inlet, it may be 
preferable to install an IAT sensor downstream of the intercooler to accurately measure 
charge temperatures.  
  
 
 
 
EMS Fuel Map, Boost Fuel Trim Table 
The 30-6820 calibration maps provided utilize the “Boost Fuel Trim Table” to provide a 1:1 
fuel compensation above and below atmospheric pressure. To use this table, the “Boost Fuel 
Trim Table” should be configured to provide twice as much fuel when the manifold pressure 
is twice as high and half the fuel when the manifold pressure is half as high; this should help 
simplify the tuning process for different vacuum and boost levels. Notice the values in the 
main “Fuel Map” do not change significantly above 100 kPa (0 psi boost), the fuel correction 
is being made by the “Boost Fuel Trim Table.”  
Note: the “Boost Fuel Trim Table” must be adjusted if a different MAP sensor is installed or if 
the Load breakpoints are adjusted. The Boost Fuel Trim value should be set to -90 at 10kPa, 
0 at 100 kPa, +100 at 200 kPa, +200 at 300 kPa, etc… 
   
 
Check Engine Light 
The  Low  Side  10  output  (LS10)  activates  the  Check  Engine  Light  on  the  gauge  cluster.  It  is 
configured  to  activate  at low RPM  in  the  AEM  startup  calibrations;  this  can  be  reconfigured 
by selecting Tools>>Configure Outputs. 
 
 
  
						

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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 event of a component 
failure, the system will shut down the ETC system and, if necessary, the engine in a graceful manner.  It still 
remains the user’s responsibility to ensure that all vehicle, component, and wiring systems are maintained to a 
level of workmanship consistent with industry standards.   
Note:  As the EMS is intended for use on vehicles that are to be operated off-road only, the factory cruise 
control system will be non-operational after installation of the EMS. 
 
Installation Information 
The 30-6820 AEM EMS was designed to work with the vehicle, its components, and wiring as delivered from 
the manufacturer.  If any of the components or wiring have been changed or if the drive-line from the original 
vehicle has been placed in another vehicle such in a custom race application then the user should take heed of 
the following notes. 
 
A mechanical W ide Open Throttle/”WOT” accelerator pedal travel stop is installed in the floor and/or carpet of 
the vehicle as delivered from the manufacturer.  If this stop is removed for any reason, such as removing the 
carpet for use in a race vehicle, the user must ensure that a stop of some sort is fabricated and installed.  This 
stop must be fabricated such that there is a minimum clearance of 0.250 inches between the accelerator pedal 
mounting bracket and the accelerator pedal actuating rod when the pedal is at WOT.  See Figure 1. 
 
Figure 1 - Minimum Pedal to Bracket Clearance 
 
The CRUISE and SET/COAST buttons, and the CRUISE and SET dashboard indicator lights are an integral 
part of the ETC system calibration and diagnostic functions.  It is, therefore, not recommended that these 
buttons and lights be completely removed from the vehicle such as could be the case with a purpose-built race 
vehicle. If the OEM steering wheel and/or gauge cluster have been removed, please temporarily re-install them 
to calibrate the ETC unit, or add switches and lights to the vehicle as shown:   
						

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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 time any part of the ETC system has been serviced, removed, or replaced. 
 
Note: Do not attempt to start or run the engine during the calibration procedure.  The EMS will disable engine 
start/running whilst in calibration mode. 
  Figure 2 - “CRUISE” and “SET/COAST” buttons Figure 3 -“CRUISE” and “SET” indicator lights 
 
 
1. Initial Calibration Procedure 
a. Turn the ignition key to the ON position.  The CRUISE and SET indicator lights will begin flashing in 
unison at a medium rate. 
b. Press and hold the CRUISE button (See Figure 4) for approximately three (3) seconds until the 
indicator lights stop flashing. 
c. There will be a brief delay after which the CRUISE light will flash once. 
d. Ensure the accelerator pedal is not being depressed and is in the full “UP” position. 
e. The SET indicator light will flash rapidly for a few seconds as the EMS calibrates this position. 
f. There will be a brief delay after which the CRUISE light will flash twice. 
g. Depress and hold the accelerator pedal to the floor and ensure it is in the full W ide Open 
Throttle/“WOT” position. 
h. The SET indicator light will flash rapidly for a few seconds as the EMS calibrates this position. 
i. There will be a brief delay after which the CRUISE light will flash three times. 
j. The SET indicator light will flash rapidly for several seconds as the EMS calibrates the ETC throttle 
body. 
k. If the calibration procedure was successful and all the ETC sensors and actuators are found to be 
within tolerance then the CRUISE and SET indicator lights will flash in unison at a medium rate. 
l. If the calibration procedure fails, indicated by the CRUISE and SET indicator lights flashing in an 
alternating pattern, please reference the sections entitled ETC Diagnostics and Calibration 
Troubleshooting elsewhere in this document. 
m. Turn the ignition key to the OFF position. 
n. The ETC system is now calibrated and ready for use. 
 Figure 4 – Pressing the “CRUISE” button 
  
						

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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 procedure has been performed, it should not need to be re-calibrated unless 
one or more of the following is true: 
 The APP sensor, TPS, or throttle body have been removed, replaced, or adjusted. 
 The EMS has been removed and installed in a different vehicle. 
 AEM Technical Support has requested it to be performed. 
The following procedure describes the steps to re-activate calibration mode on a system that has already been 
calibrated. 
 
Activate Calibration Mode 
a. Ensure the ignition key is in the OFF position. 
b. Press and HOLD both the CRUISE and SET/COAST buttons.  Please note that the CRUISE button is 
activated by pressing the end of the Cruise Control Steering Column Stalk and the SET/COAST button 
is activated by pulling the entire stalk downward as depicted in Figure 5.  Both buttons must be 
depressed and held prior to moving on to the next step. 
 
 
 
 
 
 
 
 
 
 
 
 
 
c. Turn the ignition key to the ON position. 
d. Keep holding both the CRUISE and SET/COAST buttons for approximately ten (10) seconds until the 
CRUISE and SET indicator lights (Figure 3) begin flashing in unison at a medium rate. 
e. Release the CRUISE and SET/COAST buttons. 
f. Calibration mode has now been activated.  Follow the steps in Electronic Throttle Control System 
Calibration Procedure – Initial Calibration Procedure to complete the process. 
 
 
  Figure 5 - Pressing the “SET/COAST” and “CRUISE” buttons  
						

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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 highlighted have been set up for stable idle control in the 30-6820 startup calibration but are, however, 
available for adjustment as the calibrator sees fit. 
 
Idle On if TP Less  = 13% 
Idle Off if TP Over = 13% 
Idle Invert = ON 
Idle FB Dir Invert = ON 
Idle PW Frequency = 10000.0 uS 
 
 
  
ETC Fault Management 
The ETC system continuously monitors itself for proper operation.  If a fault is detected then the system will be 
placed in a failsafe mode and power to the electronic throttle body will be turned off.  This will allow the engine 
to start and idle at approximately 1500-2000 rpm as a “limp-home” mode but the throttle body will not respond 
to accelerator pedal inputs. 
 
The system will continue to monitor itself and assume that the throttle blade will be in its rest position while in 
this un-powered failsafe mode.  If it is detected that this is not the case then the system will enter a second 
failsafe stage whereby the crank signal to the EMS is interrupted. The tachometer will drop to zero and the 
EMS will not fire fuel injectors or ignition coils. If the engine is running, it will coast to a stop. If the engine is not 
running, it will not start.  
 
 
ETC Diagnostics 
The AEM EMS ETC system uses the CRUISE and SET indicator lights on the dashboard to display diagnostic 
information to the user.  The indicator lights flash in different ways for different purposes as described in the 
following sections. 
 Figure 9 - CRUISE and SET Indicator Lights as diagnostic outputs 
 
Boot-Up 
When the ignition key is turned on and the EMS is powered up, both of the CRUISE and SET indicator 
lights will flash briefly to signify the ETC system has booted up and that the indicator lights are 
functioning properly. 
 
Fault Detected 
When the ETC system detects a fault, the CRUISE and SET indicator lights will flash in an alternating 
fashion to alert the user a fault has been detected.  This will happen in one of two situations: 
 
1. Calibration Fault – A failed calibration will be detected if one of the sensors is found to be out of 
the expected range during the calibration procedure.  The indicator lights will flash in an 
alternating pattern to alert the user of this fault for a period of approximately twenty (20) 
seconds.  After this time period, the CRUISE light will remain off and the SET indicator light will 
flash a fault code.  Please reference Table 1 for a description of the fault codes.  The system 
will flash the code repeatedly until the ignition is turned off. 
  
						

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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 lights will flash the fault 
code for the affected system. The affected ETC system code will be first flashed on the 
CRUISE light after which the failure type will be flashed on the SET light.  These codes are 
listed in Table 2 and Table 3.  The ETC system will remain un-activated until the following boot-
up cycle, i.e. key-off then key-on. 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
Troubleshooting Calibration Faults 
 
A calibration fault will be reported if the Accelerator Pedal Position (APP) or Throttle Position Sensor 
(TPS) sensors are found to be outside of the specification limits.  Table 4 details the electrical limits for 
these sensors. 
 
Sensor Mechanical Position Voltage Limit (VDC) 
APP1 ( Main ) Minimum ( Idle ) 1.00 ± 0.35 
Maximum ( WOT ) 4.00 ± 0.45 
APP2 ( Sub ) Minimum ( Idle ) 1.00 ± 0.35 
Maximum ( WOT ) 4.00 ± 0.45 
TPS1 ( Main ) Minimum ( Idle ) 0.70 ± 0.30 
Maximum ( WOT ) 4.10 ± 0.45 
TPS2 ( Sub ) Minimum ( Idle ) 1.45 ± 0.30 
Maximum ( WOT ) 4.10 ± 0.45 
Table 4 – Sensor Electrical Calibration Limits 
 
A fault code of “5 - RP / Relay” may be caused by a fouled throttle bore, a malfunctioning or missing 
ETC relay, or if the throttle body has mechanically failed. 
Calibration Faults 
1 APP Minimum 
2 APP Maximum 
3 TPS Minimum 
4 TPS Maximum 
5 RP / Relay 
Table 1 – System Fault Code 
Operational Fault – Failure Type 
N Out of Range 
O Noise 
P Disagreement 
4 General 
R F2 
S N/A 
T N/A 
U N/A 
V N/A 
Table 3 – Failure Type Fault Code 
Operational Fault - System 
1 APP 
2 TPSA 
3 TPSB 
4 Target 
5 System Voltage 
6 Motor Driver 
7 WDR 
8 EEPROM 
9 N/A 
Table 2 – System Fault Code