AEM Series 2 Plug Play EMS 306821 User Manual

Page 11 of 21 
Troubleshooting Operational Faults 
 
Should an operational fault be detected, please read and follow the following suggestions for each 
system. 
 
APP 
 Ensure the accelerator pedal position sensor is in good condition and plugged in. 
 Double-check that APP sensor is wired per OEM specifications. 
 Check all wiring for shorts or intermittent connections. 
 
TPSA/TPSB 
 Ensure the throttle position sensor is in good condition and plugged in. 
 Double-check that throttle body/TPS...

Page 12 of 21 
 
 
Wiring accessories to the EMS 
Please  follow  this  suggested  wiring  diagram  when  adding new accessories and  retaining 
original  accessories such  as  the multiplex  coolant  temperature  gauge,  air  conditioning 
switch, reverse lockout, UEGO gauges, MAP sensors, IAT sensors, or switches for use with 
the EMS. Note that wire polarity is not important for the Air Temperature sensor.   
 
 
30-1820 (Series 1) vs 30-6820 (Series 2) EMS differences: 
The EMS functions assigned to...

Page 13 of 21 
1) Install AEMTuner software onto your PC  
The latest version of the AEMTuner software can be downloaded from the AEMTuner 
section of the AEM Performance Electronics forums found at www.aemelectronics.com  
Series 2 units are not supported by the older AEMPro tuning software.  
 
2) Remove the Stock Engine Control Unit 
a) Disconnect negative terminal from battery 
b) Access the stock Engine Control Unit (ECU). The location of the ECU on the WRX is 
underneath the passenger side...

Page 14 of 21 
 
4) Ready to begin tuning the vehicle. 
a) Before  starting  the  engine,  verify  that  the  fuel  pump  runs  for  a  couple  of  seconds 
when the key is turned on and there is sufficient pressure at the fuel rail.  
If  a  MAP  sensor  is  installed,  check  that  the  Engine  Load  indicates  something  near 
atmospheric  pressure  (approximately  101kPa  or  0  PSI  at  sea  level)  with  the  key  on 
and  engine  off.  Press  the  throttle  and  verify  that  the  ‘Throttle’...

Page 15 of 21 
 
5) Troubleshooting an engine that will not start 
a) Double-check  all  the  basics  first. Engines  need  air,  fuel,  compression,  and  a 
correctly-timed  spark  event.  If  any  of  these  are  lacking,  we  suggest checking  simple 
things  first.  Depending  on  the  symptoms,  it  may  be  best  to  inspect  fuses,  sufficient 
battery  voltage,  properly  mated  wiring  connectors,  spark  using  a  timing  light  or  by 
removing  the  spark  plug,  wiring  continuity  tests,...

Page 16 of 21 
Application Notes for EMS P/N 30-6820 / 30-6821 
Subaru Impreza WRX STI (USDM 2.5L) 
Make: Subaru   Description Function ECU Pin # 
Model: Impreza WRX STI  Spare Injector Driver (max 1.5A): Injector 5 C2 
Years Covered: 2004 (30-6820 EMS) 2005-2006 (30-6821 EMS)  Spare Injector Driver (max 1.5A): Injector 6 C1 
Engine Displacement: 2.5L  Spare Injector Driver (max 1.5A): Injector 7 A6 
Engine Configuration: Flat 4  Spare Injector Driver (max 1.5A): Injector 8 A7 
Firing Order: 1-3-2-4...

Page 17 of 21 
Connection Diagram for EMS P/N 30-6820 
PnP The Plug and Play system comes with this configured for proper operation of this device. It is available for reassignment. 
Available The function is not currently allocated and is available for use 
Dedicated The location is fixed and cannot be changed 
Not used The AEM EMS does not use this pin location for this application  
Pin  2004 STI 2.5L / 2005-2006 STI 2.5L AEM EMS 30-6820  EMS I/O EMS pin description 
A1 Clutch Switch Switch 3 In...

Page 18 of 21 
  
Pin  2004 STI 2.5L / 2005-2006 STI 2.5L AEM EMS 30-6820  EMS I/O EMS pin description 
B1 GND (Power Supply) Power Ground In Dedicated, also A34,B4,B12,B31,C32,C33,D1,D2,D7,D31 
B2 Rear Oxygen Sensor heater signal ---   Not Used 
B3 --- ---   Not Used 
B4 GND (Power Supply) Power Ground In Dedicated, also A34,B1,B12,B31,C32,C33,D1,D2,D7,D31 
B5 Control Unit Power Supply +12V Switched Ignition Power In Dedicated, also connects to A18, A19, B6 
B6 Control Unit Power Supply +12V Switched...

Page 19 of 21 
 
  
Pin  2004 STI 2.5L / 2005-2006 STI 2.5L AEM EMS 30-6820  EMS I/O EMS pin description 
C1 --- Injector 6  Out Available, can be used for additional injectors (1.5A max) 
C2 --- Injector 5 Out Available, can be used for additional injectors (1.5A max) 
C3 Fuel Injector #4 Injector 4 Out PnP for Injector 4  (Peak & Hold  4A / 1A  driver) 
C4 Fuel Injector #3 Injector 3 Out PnP for Injector 3  (Peak & Hold  4A / 1A  driver) 
C5 Fuel Injector #2 Injector 2 Out PnP for Injector 2  (Peak &...

Page 20 of 21 
 
  
Pin  2004 STI 2.5L / 2005-2006 STI 2.5L AEM EMS 30-6820  EMS I/O EMS pin description 
D1 GND (control systems) Power Ground In Dedicated, also A34,B1, B4,B12,B31,C32,C33,D2,D7,D31 
D2 GND (control systems) Power Ground In Dedicated, also A34,B1, B4,B12,B31,C32,C33,D1, D7,D31 
D3 Electronic Throttle control GND (sensor) Electronic Throttle Ground Out Dedicated 
D4 Electronic Throttle control motor (-) Electronic Throttle Motor -  Out Dedicated, ETC system output 
D5 Electronic Throttle...