Not confident with automotive wiring? Have a professional harness builder or tuner do it, or check your work before first power-up. A wiring mistake can damage the ECU, the engine or the car, or start a fire.
100%
Stock ECU being replaced
GND
GND
MAIN-R-COIL+ Relay coil positive (ignition-switched +12V)
G4XXTREMEX-A-A19 Aux 3
ECM power (J271 relay feed)
G4XXTREMEX-B-B3 Injector 6
G4XXTREMEX-A-A29 Aux 5
G4XXTREMEX-A-A31 Digital Input 2
0V sensor
G4XXTREMEX-A-A33 Analog Volt 3
0V sensor
G4XXTREMEX-B-B33 Analog Volt 5
0V sensor
G4XXTREMEX-A-A23 Digital Input 3
G4XXTREMEX-B-B21 Digital Input 4
G4XXTREMEX-B-B20 Digital Input 5
G4XXTREMEX-B-B19 Digital Input 6
G4XXTREMEX-B-B2 Injector 7
G4XXTREMEX-B-B1 Injector 8
G4XXTREMEX-B-B30 Digital Input 7
G4XXTREMEX-A-A17 Analog Volt 1
G4XXTREMEX-A-A30 Digital Input 1
G4XXTREMEX-B-B29 Digital Input 8
G4XXTREMEX-B-B24 Analog Volt 9
G4XXTREMEX-B-B31 Analog Volt 10
G4XXTREMEX-B-B28 CAN 2 L
G4XXTREMEX-B-B27 CAN 2 H
G4XXTREMEX-A-A18 Aux 4
G4XXTREMEX-A-A21 Aux 1
G4XXTREMEX-A-A20 Aux 2
G4XXTREMEX-B-B32 Analog Volt 11
G4XXTREMEX-B-B16 Analog Volt 7
G4XXTREMEX-B-B23 Analog Volt 8
5V ref
5V ref
G4XXTREMEX-A-A28 Aux 6
G4XXTREMEX-A-A8 Trigger 1
5V ref
G4XXTREMEX-A-A14 Analog Volt 4
G4XXTREMEX-A-A16 Analog Temp 2
G4XXTREMEX-A-A9 Trigger 2
G4XXTREMEX-A-A1 Injector 4
G4XXTREMEX-A-A3 Injector 2
0V sensor
0V sensor
G4XXTREMEX-B-B15 Analog Volt 6
G4XXTREMEX-A-A15 Analog Temp 1
G4XXTREMEX-A-A10 Ignition 4
G4XXTREMEX-A-A12 Ignition 2
G4XXTREMEX-A-A4 Injector 1
G4XXTREMEX-A-A2 Injector 3
5V ref
5V ref
G4XXTREMEX-A-A22 Analog Volt 2
G4XXTREMEX-A-A13 Ignition 1
G4XXTREMEX-A-A11 Ignition 3
G4XXTREMEX-A-A27 Aux 7
G4XXTREMEX-A-A26 Aux 8
G4XXTREMEX-B-B9 Knock 1
G4XXTREMEX-B-B8 Knock 2
0V sensor
G4XXTREMEX-B-B4 Injector 5
G4XXTREMEX-B-B18 Aux 9
G4XXTREMEX-B-B26 Aux 10
ECM + coil power (J271 relay feed)
OEM-T121
Stock ECU being replaced
1ECU ground
2ECU ground
3Ignition switch +12V (term 15)
5Wideband lambda heater (Z19)
21ECM power (J271 relay feed)
22Brake vacuum pump (V192)
25V144 Evaporative diagnostic pump (Pin 2)
28Alternator DF terminal (charge warning)
29MAF sensor ground (G70)
33Accelerator pedal position 1 (G79)
34Accelerator pedal position 1 ground (G79)
35Accelerator pedal position 2 (G185)
36Accelerator pedal position 2 ground (G185)
38Cruise control switch (E45)
39Clutch pedal switch (F36)
40A/C signal
41A/C signal
47Check engine light (MIL)
48EPC warning light
49Power steering pressure switch (F88)
53MAF sensor signal (G70)
54Road speed signal (VSS)
55Brake pedal switch (F)
56Brake pedal switch (F)
57Cruise control switch (E45)
58CAN bus low
60CAN bus high
63Post-cat lambda heater (Z29)
65Fuel pump relay control
66Secondary-air pump relay (J299)
67Crash sensor signal
68Post-cat lambda signal (G130)
69Post-cat lambda signal (G130)
72Accelerator pedal position 1 5V supply (G79)
73Accelerator pedal position 2 5V supply (G185)
80V144 Evap Diagnostic Pump (Pin 1)
82Crank position sensor (G28)
83Throttle position sensor 5V supply (G187/G188)
84Throttle position sensor 1 (G187)
85Intake air temperature (G42)
86Camshaft position sensor (G40)
88Injector 4 (N33)
89Injector 2 (N31)
90Crank position sensor ground (G28)
91Throttle position sensor ground (G187/G188)
92Throttle position sensor 2 (G188)
93Engine coolant temperature (G62)
94Ignition coil 4 (N163)
95Ignition coil 2 (N128)
96Injector 1 (N30)
97Injector 3 (N32)
98Cam + boost sensor 5V supply (G40/G31)
99Knock sensor 5V supply (G61/G66)
101Boost pressure sensor (G31)
102Ignition coil 1 (N127)
103Ignition coil 3 (N158)
104Boost control solenoid (N75)
105Diverter valve (N249)
106Knock sensor 1 (G61)
107Knock sensor 2 (G66)
108Sensor ground
115VVT camshaft adjustment valve (N205)
117Throttle motor G186 (+)
118Throttle motor G186 (−)
121ECM + coil power (J271 relay feed)
G4XXTREMEX
G4XXTREMEX-A
G4XXTREMEX
A1Injector 4
A2Injector 3
A3Injector 2
A4Injector 1
A5+14V ECU Power
A8Trigger 1
A9Trigger 2
A10Ignition 4
A11Ignition 3
A12Ignition 2
A13Ignition 1
A14Analog Volt 4
A15Analog Temp 1
A16Analog Temp 2
A17Analog Volt 1
A18Aux 4
A19Aux 3
A20Aux 2
A21Aux 1
A22Analog Volt 2
A23Digital Input 3
A24Sensor Ground
A25System Ground
A26Aux 8
A27Aux 7
A28Aux 6
A29Aux 5
A30Digital Input 1
A31Digital Input 2
A32+5V Out
A33Analog Volt 3
A34System Ground
OEM-T121-88 Injector 4 (N33)
OEM-T121-97 Injector 3 (N32)
OEM-T121-89 Injector 2 (N31)
OEM-T121-96 Injector 1 (N30)
+14V ECU Power
OEM-T121-82 Crank position sensor (G28)
OEM-T121-86 Camshaft position sensor (G40)
OEM-T121-94 Ignition coil 4 (N163)
OEM-T121-103 Ignition coil 3 (N158)
OEM-T121-95 Ignition coil 2 (N128)
OEM-T121-102 Ignition coil 1 (N127)
OEM-T121-84 Throttle position sensor 1 (G187)
OEM-T121-93 Engine coolant temperature (G62)
OEM-T121-85 Intake air temperature (G42)
OEM-T121-53 MAF sensor signal (G70)
OEM-T121-63 Post-cat lambda heater (Z29)
OEM-T121-5 Wideband lambda heater (Z19)
OEM-T121-66 Secondary-air pump relay (J299)
OEM-T121-65 Fuel pump relay control
OEM-T121-101 Boost pressure sensor (G31)
OEM-T121-38 Cruise control switch (E45)
0V sensor
GND
OEM-T121-105 Diverter valve (N249)
OEM-T121-104 Boost control solenoid (N75)
OEM-T121-80 V144 Evap Diagnostic Pump (Pin 1)
OEM-T121-25 V144 Evaporative diagnostic pump (Pin 2)
OEM-T121-54 Road speed signal (VSS)
OEM-T121-28 Alternator DF terminal (charge warning)
5V ref
OEM-T121-33 Accelerator pedal position 1 (G79)
GND
G4XXTREMEX-B
G4XXTREMEX
B1Injector 8
B2Injector 7
B3Injector 6
B4Injector 5
B5Aux 9/10 E-Throttle Supply
B8Knock 2
B9Knock 1
B15Analog Volt 6
B16Analog Volt 7
B18Aux 9
B19Digital Input 6
B20Digital Input 5
B21Digital Input 4
B22Sensor Ground
B23Analog Volt 8
B24Analog Volt 9
B25System Ground
B26Aux 10
B27CAN 2 H
B28CAN 2 L
B29Digital Input 8
B30Digital Input 7
B31Analog Volt 10
B32Analog Volt 11
B33Analog Volt 5
B34System Ground
OEM-T121-48 EPC warning light
OEM-T121-47 Check engine light (MIL)
OEM-T121-22 Brake vacuum pump (V192)
OEM-T121-115 VVT camshaft adjustment valve (N205)
Aux 9/10 E-Throttle Supply
OEM-T121-107 Knock sensor 2 (G66)
OEM-T121-106 Knock sensor 1 (G61)
OEM-T121-92 Throttle position sensor 2 (G188)
OEM-T121-68 Post-cat lambda signal (G130)
OEM-T121-117 Throttle motor G186 (+)
OEM-T121-41 A/C signal
OEM-T121-40 A/C signal
OEM-T121-39 Clutch pedal switch (F36)
0V sensor
OEM-T121-69 Post-cat lambda signal (G130)
OEM-T121-56 Brake pedal switch (F)
GND
OEM-T121-118 Throttle motor G186 (−)
OEM-T121-60 CAN bus high
OEM-T121-58 CAN bus low
OEM-T121-55 Brake pedal switch (F)
OEM-T121-49 Power steering pressure switch (F88)
OEM-T121-57 Cruise control switch (E45)
OEM-T121-67 Crash sensor signal
OEM-T121-35 Accelerator pedal position 2 (G185)
GND
MAIN
MAIN-R
MAIN
INRelay contact input (battery + via main fuse)
OUTRelay contact output (switched +12V bus)
COIL+Relay coil positive (ignition-switched +12V)
COIL-Relay coil negative (ECU low-side driver)
NEW-BATT
G4XXTREMEX-A-A5 +14V ECU Power
Relay coil positive (ignition-switched +12V)
SP-GND · 6 pins
SP-0V · 9 pins
SP-GND · 8 pins
SP-14V · 4 pins
SP-5V1 · 7 pins
◯New feed: NEW-BATT
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