AEM EMS-4 is a 36-pin wire-in AEM ECU on 1 connector: C (36 pins).
It has 4 injector outputs and 4 ignition outputs. The injector drivers are saturated, which means high-impedance injectors. Low-impedance ones need a ballast resistor pack or a different ECU. The ignition outputs are logic-level. Smart coils plug straight in; dumb coils need an igniter in between.
There are 4 dedicated trigger inputs; the maker does not say which sensor type. One knock input covers an inline engine. Wideband control needs an external controller, usually over CAN.
The maker does not list drive-by-wire outputs. One CAN bus handles dashes, PDMs and expansion.
Spec sheet
| Connectors | C (36)36 pins in this profile |
|---|---|
| Injector outputs | 4saturated (high-impedance only) |
| Ignition outputs | 4logic-level: smart coils, or an igniter for dumb coils |
| Dedicated trigger inputs | 4sensor type not stated |
| Knock inputs | 1 |
| Onboard wideband controllers | 0 |
| Onboard MAP sensor | Not listed by the maker |
| CAN buses | 1 |
| Drive-by-wire | Not stated by the maker |
| High-side outputs | 0 |
| Half-bridge outputs | 0 |
| 5V sensor supply | 1 pin |
Which builds it suits
Of the 58 swap presets in the planner, 0 fit as they are and 6 fit with add-ons; 52 do not fit at all. The add-on it asks for most often is the AEM X-Series Inline Wideband UEGO (30-0310). Where it falls short, it is usually not enough injector output (low-side). The planner fills anything a preset leaves open with its ordinary defaults, so your own build may land differently.
The Nissan SR20DET (S15) needs AEM X-Series Inline Wideband UEGO (30-0310). The Mazda Rotary 13B-REW (FD RX-7) needs a CAN I/O expander and AEM X-Series Inline Wideband UEGO (30-0310). It can't run the GM LT1 (Gen5 6.2 alum): not enough injector output (low-side). It can't run the Nissan RB26DETT (R32/R33, dumb coils): not enough injector output (low-side).
Fits with add-ons 6
- Nissan SR20DET (S13) with AEM X-Series Inline Wideband UEGO (30-0310), an external igniter
- Nissan SR20DET (S14) with AEM X-Series Inline Wideband UEGO (30-0310), an external igniter
- Nissan SR20DET (S15) with AEM X-Series Inline Wideband UEGO (30-0310)
- Subaru EJ/FA EJ20 turbo single-AVCS (EJ207 v7-9) with AEM X-Series Inline Wideband UEGO (30-0310)
- Subaru EJ/FA EJ20 turbo dual-AVCS (EJ207 GRB 2008+) with a CAN I/O expander, AEM X-Series Inline Wideband UEGO (30-0310)
- Mazda Rotary 13B-REW (FD RX-7) with a CAN I/O expander, AEM X-Series Inline Wideband UEGO (30-0310)
Does not fit 52
- Toyota 1JZ-GE distributor (NA, early) not enough injector output (low-side)
- Toyota 1JZ-GE VVT-i (coil pack) not enough injector output (low-side)
- Toyota 1JZ-GTE non-VVTi not enough injector output (low-side)
- Toyota 1JZ-GTE VVTi not enough injector output (low-side)
- Toyota 2JZ-GE distributor (NA, early) not enough injector output (low-side)
- Toyota 2JZ-GE VVT-i (coil pack) not enough injector output (low-side)
- Toyota 2JZ-GTE non-VVTi not enough injector output (low-side)
- Toyota 2JZ-GTE VVTi not enough injector output (low-side)
- GM LS1 (Gen3 5.7 alum) not enough injector output (low-side)
- GM LS6 (Gen3 5.7 alum) not enough injector output (low-side)
- GM LS LQ4/LQ9 (Gen3 6.0 iron) not enough injector output (low-side)
- GM LS2 (Gen4 6.0 alum) not enough injector output (low-side)
- GM LS3 (Gen4 6.2 alum, car) not enough injector output (low-side)
- GM LS L76 (Gen4 6.0 alum) not enough injector output (low-side)
- GM LS L92 (Gen4 6.2 alum) not enough injector output (low-side)
- GM LS LY6/L96 (Gen4 6.0 iron) not enough injector output (low-side)
- GM LSA (Gen4 6.2 alum, S/C) not enough injector output (low-side)
- GM LT1 (Gen5 6.2 alum) not enough injector output (low-side)
- GM LT4 (Gen5 6.2 alum, S/C) not enough injector output (low-side)
- Ford Coyote 5.0 Gen1 (2011-14) not enough injector output (low-side)
- Ford Coyote 5.0 Gen2 (2015-17) not enough injector output (low-side)
- Ford Coyote 5.0 Gen3 (2018-23) not enough injector output (low-side)
- Ford Modular 4.6 2V (SOHC) not enough injector output (low-side)
- Ford Modular 4.6 4V Cobra (NA, cable) not enough injector output (low-side)
- Ford Modular 4.6 4V Terminator (S/C, cable) not enough injector output (low-side)
- Ford Modular 5.4 4V Ford GT (S/C, cable) not enough injector output (low-side)
- Ford Modular 5.4 4V GT500 (S/C, DBW) not enough injector output (low-side)
- Ford Coyote Voodoo 5.2 (GT350, flat-plane) not enough injector output (low-side)
- Ford Coyote Predator 5.2 (GT500, cross-plane, S/C) not enough injector output (low-side)
- Ford Barra 4.0 NA (182/190/195) not enough injector output (low-side)
- Ford Barra 4.0 Turbo (240T/245T/270T/310T/325T) not enough injector output (low-side)
- Nissan RB20DET not enough injector output (low-side)
- Nissan RB25DET non-Neo S1 (R33, dumb coils) not enough injector output (low-side)
- Nissan RB25DET non-Neo S2 (R33, smart coils) not enough injector output (low-side)
- Nissan RB25DET Neo (R34) not enough injector output (low-side)
- Nissan RB26DETT (R32/R33, dumb coils) not enough injector output (low-side)
- Nissan RB26DETT (R34, smart coils) not enough injector output (low-side)
- Nissan VR38DETT (R35 GT-R) not enough injector output (low-side)
- Nissan VQ35DE (base, 2003-04) not enough injector output (low-side)
- Nissan VQ35DE Rev-Up (2005-06) not enough injector output (low-side)
- Nissan VQ35HR (High-Rev, 2007+) not enough injector output (low-side)
- Honda K20 (i-VTEC 2.0 NA) not enough drive-by-wire throttle motor (h-bridge)
- Honda K24 (i-VTEC 2.4 NA) not enough drive-by-wire throttle motor (h-bridge)
- Subaru EJ/FA EJ25 turbo single-AVCS (EJ257 2004-07) not enough drive-by-wire throttle motor (h-bridge)
- Subaru EJ/FA EJ25 turbo dual-AVCS (EJ257 2008+) not enough drive-by-wire throttle motor (h-bridge)
- Subaru EJ/FA FA20D (BRZ/86 NA) not enough drive-by-wire throttle motor (h-bridge)
- Subaru EJ/FA FA20DIT (WRX turbo 2015+) not enough drive-by-wire throttle motor (h-bridge)
- Mazda Rotary 13B-MSP Renesis (RX-8 manual, 6-injector) not enough drive-by-wire throttle motor (h-bridge)
- Mazda Rotary 13B-MSP Renesis (RX-8 auto, 4-injector) not enough drive-by-wire throttle motor (h-bridge)
- Mazda Rotary 20B (Eunos Cosmo 3-rotor) not enough ignition outputs
- BMW S54 (3.2 NA I6, E46 M3) not enough injector output (low-side)
- BMW N54 (3.0 twin-turbo I6) not enough injector output (low-side)
Plan a build around the AEM EMS-4
Pin table
Connector C carries 4 injector outputs, 4 ignition outputs and 4 trigger inputs.
Show all 36 pins
| Pin | Function |
|---|---|
| C 1 | Switched +12V input |
| C 2 | Injector #1 |
| C 3 | Injector #2 |
| C 4 | Injector #3 |
| C 5 | Injector #4 |
| C 6 | Coil 1 output |
| C 7 | Coil 2 output |
| C 8 | Coil 3 output |
| C 9 | Coil 4 output |
| C 10 | GPIO #1 |
| C 11 | GPIO #2 |
| C 12 | GPIO #3 |
| C 13 | GPIO #4 |
| C 14 | GPIO #5 |
| C 15 | GPIO #6 |
| C 16 | GPIO #7 |
| C 17 | GPIO #8 |
| C 18 | Battery neg |
| C 19 | Battery neg |
| C 20 | O2 sensor input |
| C 21 | Cam sensor mag input |
| C 22 | Crank sensor mag input |
| C 23 | VSS hall input |
| C 24 | Cam sensor hall input |
| C 25 | Crank sensor hall input |
| C 26 | Knock sensor #1 input |
| C 27 | Throttle position sensor |
| C 28 | Manifold pressure sensor |
| C 29 | Coolant temp sensor |
| C 30 | Inlet air temp sensor |
| C 31 | USB data - |
| C 32 | USB data + |
| C 33 | CAN + |
| C 34 | CAN - |
| C 35 | Sensor ground |
| C 36 | VCC |
Other AEM ECUs
The closest AEM unit is the AEM Infinity Series 3. Against it, this one has 4 injector outputs (the Infinity Series 3 has 10), 4 ignition outputs (the Infinity Series 3 has 9), 1 knock input (the Infinity Series 3 has 2) and 36 pins (the Infinity Series 3 has 73).
Source: AEM documentation for the EMS-4
Always verify against the manufacturer's manual and your tuner before wiring.