For those new to VEMS, the ECIII header on these tables is just the name for the large connectors on the VEMS box. Number in setup refers to the name of the function when using MegaTune.
Power
| Power |
| Wire Color | Use | number in setup | ECIII pin |
| Black/Red | EFI Relay #1 | +13.8VBATT | 25 |
| Grounds |
| Wire Color | Use | number in setup | ECIII pin |
| Brown | ground to CLT | GND | 26 |
| Brown | ground to TPS | GND | 26 |
| Brown | ground to IAT | GND | 26 |
| Brown | ground to GND5 & chassis close to ECU | GND | 26 |
| Coax Sheild | ground to CAM Triggers | GND | 26 |
| Black | power grounds 2 each to intake | GND5 | 32 |
| Black | power grounds to intake | GND5 | 21 |
| Black | ground to GND & chassis close to ECU | GND5 | 21 |
| Black | power grounds 2 each to intake | GND5 | 5 |
TPS
| TPS switch |
| Wire Color | Use | number in setup | ECIII pin |
| Red | Wiper | TPS | pin1 |
| Light Blue/Red | PWR | TPS5V | pin28 |
| Brown | common | GND | pin26 |
| Light Blue | Switch | | |
Injectors
| Injector |
| Wire Color | Injector | number in setup | ECIII pin |
| Yellow | Injector power | EFI Relay | |
| | Injector #1 | INJA | pin7 |
| | Injector #2 | INJB | pin19 |
| | Injector #3 | INJC | pin8 |
| | Injector #4 | INJD | pin20 |
Coils setup
| The pairs I will use so I can run wasted is |
| Wire Color | Transistor | number in setup | ECIII pin | Cyl |
| ?? | Q16 | #0 | pin35 | 1,4 |
| ?? | Q21 | #1 | pin33 | 2,3 |
CLT
| Wire Color | Use | number in setup | ECIII pin |
| Green | CLT | CLT | 14 |
| Brown | Gnd | Gnd | 26 |
IAT
| Wire Color | Use | number in setup | ECIII pin |
| Yellow/Black | | MAT | 2 |
| Brown | Gnd | Gnd | 26 |
CAM Trigers
| CAM Trigers use coex |
| Wire Color | Use | number in setup | ECIII pin |
| Ne | coax | TRIGG1_CONN | 27 |
| G1 | coax | TRIGG2_CONN | 13 |
| G- | shield | GND | 26 |
WBO²
ground the green coex to gnd
| WBO² |
| Wire Color | Use | ECIII18 pin | WBO² pin |
| ?? | PUMP(-) | 7 | 5 |
| ?? | PUMP(+) | 9 | 6 |
| coex | NERNST_CELL1 | 13 | 1 |
| ?? | HEATER1(-) | 18 | 4 |
| ?? | Power | N/A | 3 |
| Power will come from the old wire that went to the NBO² |
Tachometer
| Tachometer |
| Wire Color | Use | number in setup | ECIII18 pin |
| Black | goes to cluster(tach) | STEP_B | 10 |
Knock
| Knock Use coex |
| Wire Color | Use | number in setup | ECIII pin |
| Blackn | KNOCK1 | | 34 |
| Shield | Knock gnd | | 36 |
Fan
| Fan Reley |
| Wire Color | Use | ECIII18 pin |
| ?? | STEP_C | 5 |
Fuel Pump Power Control
| Fuel Pump |
| Wire Color | Use | number in setup | ECIII pin |
| Green/Red | relay | STEP_A | small#4 |
IAC
Need to add a flyback diode between the pins?
| Wire Color | Use | number in setup | ECIII pin |
| Black/Blue? | will be the IAC control | INJG | pin6 |
| Black/White? | will be the IAC control | INJF | pin18 |
| Black? | Switched power | N/A | N/A |
VVT valve
| Wire Color | Use | number in setup | ECIII pin |
| ?? | ?? | ?? | ?? |
Check Engine Light
| Wire Color | Use | number in setup | ECIII pin |
| Green/White | ?? | ?? | ?? |
Charcoal Canister valve
| Wire Color | Use | number in setup | ECIII pin |
| ?? | ?? | ?? | ?? |
EGR valve
| Wire Color | Use | number in setup | ECIII pin |
| ?? | ?? | ?? | ?? |
Serial Port
| Wire Color | Use | number in setup | ECIII18 pin |
| Red | RxD | RxD | 14 |
| Brown | TxD | TxD | 15 |
C BLACK firewall connector
NOTE: Pins may have different uses on other trim models/year of AE86. This is specifically for a 1986 US spec "Kouki" GT-S with 4AG-EC (16V with EFI). Generally, auto transmission uses pin 8 for Starter Signal power and leaves 14 blank, Manual transmission uses pin 14 for the same purpose and leaves pin 8 blank.
My car has/had P/S, and A/C. Cars with out one or both will have subtle differences in the wiring. SR5s are different again.
- Pins labeled with an "X" are BLANK on my car's connector and are not used, despite the image above.**
| PIN # | Color | Function |
| 1 | Yellow/Green | Water Temp |
| 2 | Black/Orange | Injector and Coil Power |
| 3 | Red-Black | Backup Light |
| 4 | X | X |
| 5 | Black | Idle-Up |
| 6 | X | X |
| 7 | Yellow/Black | Oil Pressure Sender |
| 8 | X | Auto Tranny uses this but not M/T |
| 9 | Red/Light Blue | Backup Light (+12) |
| 10 | X | X |
| 11 | White | A/C PSI Switch |
| 12 | Black/White | A/C Clutch |
| 13 | Black | Tacho |
| 14 | Black/White | Starter Signal, STA, Cold start/Thermal time switch |
| 15 | | A/C compressor swtch |
Pin 14 is usually used to privides STA signal to 20V OEM ECUs for those not using a standalone. It is recommended to hook this up to the ECU.