MX-5 Miata NA8 1996-97 (BP-ZE, 1.8, OBD-II) → Motorsport Electronics ME221 (auto)

MX-5 Miata NA8 1996-97 (BP-ZE, 1.8, OBD-II) — Motorsport Electronics — ME221

Drawn by Michael Gnankou · Rev 0 · proposal · 2026-10-12

Before you start

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.

Status	proposal · not yet verified: nobody has reported building and running this harness
Open errors	none
Size of the job	45 wires · 7 connectors · 0 part lines
Tools	Crimp and extraction tools for each terminal family (see Connectors) · wire strippers · multimeter · heat gun + heat-shrink
Order of work	1. Check every part against the parts list. 2. Cut and label every wire (labels: Export → Wire labels). 3. Crimp and pin connector by connector, ticking the build checklist. 4. Run the bench test with nothing plugged in and the battery disconnected. 5. Only then connect the ECU and power up.

Build checklist

Tick each box as you go. Continuity: meter from end to end, expect under 1 Ω.

Wire	From	To	Gauge	Cut	Label	Crimp A	Crimp B	Pin A	Pin B	Continuity
W1	OEM-4-B	SP-14V-1	0.85	☐	☐	☐	☐	☐	☐	☐
W2	SP-14V-1	ME221-C1-15	0.85	☐	☐	☐	☐	☐	☐	☐
W3	SP-14V-1	ME221-C1-64	0.85	☐	☐	☐	☐	☐	☐	☐
W4	OEM-4-A	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W5	OEM-4-C	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W6	OEM-4-D	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W7	OEM-4-K	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W8	SP-GND-1	ME221-C1-10	0.85	☐	☐	☐	☐	☐	☐	☐
W9	SP-GND-1	ME221-C1-61	0.85	☐	☐	☐	☐	☐	☐	☐
W10	SP-GND-1	ME221-C1-89	0.85	☐	☐	☐	☐	☐	☐	☐
W11	SP-GND-1	ME221-C1-90	0.85	☐	☐	☐	☐	☐	☐	☐
W12	OEM-3-O	SP-0V-1	0.5	☐	☐	☐	☐	☐	☐	☐
W13	OEM-4-H	SP-0V-1	0.5	☐	☐	☐	☐	☐	☐	☐
W14	SP-0V-1	ME221-C1-52	0.5	☐	☐	☐	☐	☐	☐	☐
W15	SP-0V-1	ME221-C1-84	0.5	☐	☐	☐	☐	☐	☐	☐
W16	OEM-3-I	ME221-C1-45	0.5	☐	☐	☐	☐	☐	☐	☐
W17	OEM-4-E	ME221-C1-80	0.5	☐	☐	☐	☐	☐	☐	☐
W18	OEM-4-G	ME221-C1-22	0.5	☐	☐	☐	☐	☐	☐	☐
W19	OEM-4-F	ME221-C1-23	0.5	☐	☐	☐	☐	☐	☐	☐
W20	OEM-4-N	ME221-C1-32	0.5	☐	☐	☐	☐	☐	☐	☐
W21	OEM-4-R	ME221-C1-31	0.5	☐	☐	☐	☐	☐	☐	☐
W22	OEM-4-U	ME221-C1-63	0.5	☐	☐	☐	☐	☐	☐	☐
W23	OEM-4-V	ME221-C1-4	0.5	☐	☐	☐	☐	☐	☐	☐
W24	OEM-4-W	ME221-C1-33	0.5	☐	☐	☐	☐	☐	☐	☐
W25	OEM-4-X	ME221-C1-3	0.5	☐	☐	☐	☐	☐	☐	☐
W26	OEM-3-B	ME221-C1-26	0.5	☐	☐	☐	☐	☐	☐	☐
W27	OEM-3-F	ME221-C1-56	0.5	☐	☐	☐	☐	☐	☐	☐
W28	OEM-3-G	ME221-C1-86	0.5	☐	☐	☐	☐	☐	☐	☐
W29	OEM-1-A	ME221-C1-73	0.5	☐	☐	☐	☐	☐	☐	☐
W30	OEM-1-B	ME221-C1-12	0.5	☐	☐	☐	☐	☐	☐	☐
W31	OEM-1-G	ME221-C1-74	0.5	☐	☐	☐	☐	☐	☐	☐
W32	OEM-1-U	ME221-C1-44	0.5	☐	☐	☐	☐	☐	☐	☐
W33	OEM-3-M	ME221-C1-16	0.5	☐	☐	☐	☐	☐	☐	☐
W34	OEM-1-E	ME221-C1-69	0.5	☐	☐	☐	☐	☐	☐	☐
W35	OEM-4-J	ME221-C1-39	0.5	☐	☐	☐	☐	☐	☐	☐
W36	OEM-4-O	ME221-C1-37	0.5	☐	☐	☐	☐	☐	☐	☐
W37	OEM-4-P	ME221-C1-42	0.5	☐	☐	☐	☐	☐	☐	☐
W38	OEM-4-Q	ME221-C1-72	0.5	☐	☐	☐	☐	☐	☐	☐
W39	OEM-4-T	ME221-C1-43	0.5	☐	☐	☐	☐	☐	☐	☐
W40	OEM-4-L	ME221-C1-79	0.5	☐	☐	☐	☐	☐	☐	☐
W41	OEM-3-H	ME221-C1-17	0.5	☐	☐	☐	☐	☐	☐	☐
W42	OEM-3-N	ME221-C1-18	0.5	☐	☐	☐	☐	☐	☐	☐
W43	OEM-3-K	ME221-C1-57	0.5	☐	☐	☐	☐	☐	☐	☐
W44	OEM-1-M	ME221-C1-6	0.5	☐	☐	☐	☐	☐	☐	☐
W45	OEM-1-C	ME221-C1-7	0.5	☐	☐	☐	☐	☐	☐	☐

Bench test (before first power-up)

Battery disconnected, ECU and every sensor unplugged. Meter on resistance. Each pair below must read open (OL): a reading means a pinched wire, a stray strand or a mis-pinned cavity. Then check continuity of every wire (last column of the build checklist).

#	Probe A	Probe B	Expect	Why
1	ME221-C1-45	ME221-C1-10	open (OL)	5 V sensor reference must not touch power ground
2	ME221-C1-45	ME221-C1-52	open (OL)	5 V sensor reference must not touch sensor ground
3	ME221-C1-10	ME221-C1-15	open (OL)	power ground must not touch +12 V supply
4	ME221-C1-45	ME221-C1-15	open (OL)	5 V sensor reference must not touch +12 V supply
5	ME221-C1-52	ME221-C1-15	open (OL)	sensor ground must not touch +12 V supply

If any reading doesn't match, stop and get help before powering up.

Revisions

Rev	Label	By	Date
No revisions yet.

Schematic

Connectors

ME221-C1

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	COIL 4	—	—	—	—	—	—	—	—
10	GROUND CHASSIS	—	W8	—	0.85	SP-GND-1	—	—	—
12	LOW SIDE 2	—	W30	—	0.5	OEM-1-B	—	—	—
14	LSU +12V	—	—	—	—	—	—	—	—
15	IGN +12V	—	W2	—	0.85	SP-14V-1	—	—	—
16	LSU HEATER -VE	—	W33	—	0.5	OEM-3-M	—	—	—
17	ANA VOLT 3	—	W41	—	0.5	OEM-3-H	—	—	—
18	ANA VOLT 4	—	W42	—	0.5	OEM-3-N	—	—	—
19	LSU UN	—	—	—	—	—	—	—	—
2	COIL 3	—	—	—	—	—	—	—	—
20	LSU VM	—	—	—	—	—	—	—	—
21	CAN 1 HIGH	—	—	—	—	—	—	—	—
22	CAM A VR+	—	W18	—	0.5	OEM-4-G	—	—	—
23	CAM A VR-	—	W19	—	0.5	OEM-4-F	—	—	—
24	SERIAL 1 GROUND	—	—	—	—	—	—	—	—
25	SERIAL 1 TX	—	—	—	—	—	—	—	—
26	ANA VOLT 1	—	W26	—	0.5	OEM-3-B	—	—	—
3	INJECTOR 4	—	W25	—	0.5	OEM-4-X	—	—	—
31	COIL 2	—	W21	—	0.5	OEM-4-R	—	—	—
32	COIL 1	—	W20	—	0.5	OEM-4-N	—	—	—
33	INJECTOR 3	—	W24	—	0.5	OEM-4-W	—	—	—
35	USB D+	—	—	—	—	—	—	—	—
36	USB D-	—	—	—	—	—	—	—	—
37	LOW SIDE RELAY 11	—	W36	—	0.5	OEM-4-O	—	—	—
38	USB VBUS	—	—	—	—	—	—	—	—
39	LOW SIDE 6	—	W35	—	0.5	OEM-4-J	—	—	—
4	INJECTOR 2	—	W23	—	0.5	OEM-4-V	—	—	—
41	USB GROUND	—	—	—	—	—	—	—	—
42	LOW SIDE RELAY 12	—	W37	—	0.5	OEM-4-P	—	—	—
43	LOW SIDE RELAY 14	—	W39	—	0.5	OEM-4-T	—	—	—
44	LOW SIDE 4	—	W32	—	0.5	OEM-1-U	—	—	—
45	5V REF	—	W16	—	0.5	OEM-3-I	—	—	—
46	5V REF	—	—	—	—	—	—	—	—
49	LSU IA	—	—	—	—	—	—	—	—
50	LSU IP	—	—	—	—	—	—	—	—
51	CAN 1 LOW	—	—	—	—	—	—	—	—
52	SENSORS GROUND	—	W14	—	0.5	SP-0V-1	—	—	—
53	KNOCK 1 SIGNAL	—	—	—	—	—	—	—	—
55	SERIAL 1 RX	—	—	—	—	—	—	—	—
56	ANA VOLT 2	—	W27	—	0.5	OEM-3-F	—	—	—
57	ANA TEMP 2	—	W43	—	0.5	OEM-3-K	—	—	—
6	DIG_IN 1	—	W44	—	0.5	OEM-1-M	—	—	—
61	GROUND	—	W9	—	0.85	SP-GND-1	—	—	—
63	INJECTOR 1	—	W22	—	0.5	OEM-4-U	—	—	—
64	VBAT	—	W3	—	0.85	SP-14V-1	—	—	—
67	Stepper 1 / A1	—	—	—	—	—	—	—	—
68	Stepper 2 / A2	—	—	—	—	—	—	—	—
69	LOW SIDE 5	—	W34	—	0.5	OEM-1-E	—	—	—
7	DIG_IN 2	—	W45	—	0.5	OEM-1-C	—	—	—
70	Stepper 3 / B1	—	—	—	—	—	—	—	—
71	Stepper 4 / B2	—	—	—	—	—	—	—	—
72	LOW SIDE RELAY 13	—	W38	—	0.5	OEM-4-Q	—	—	—
73	LOW SIDE 1	—	W29	—	0.5	OEM-1-A	—	—	—
74	LOW SIDE 3	—	W31	—	0.5	OEM-1-G	—	—	—
76	5V REF	—	—	—	—	—	—	—	—
79	TACHOMETER	—	W40	—	0.5	OEM-4-L	—	—	—
80	CRANK VR+	—	W17	—	0.5	OEM-4-E	—	—	—
81	CRANK VR-	—	—	—	—	—	—	—	—
84	Sensor Ground	—	W15	—	0.5	SP-0V-1	—	—	—
86	ANA TEMP 1	—	W28	—	0.5	OEM-3-G	—	—	—
89	GROUND	—	W10	—	0.85	SP-GND-1	—	—	—
90	GROUND	—	W11	—	0.85	SP-GND-1	—	—	—

OEM-1

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
A	Cooling fan relay (low-side)	—	W29	—	0.5	ME221-C1-73	—	—	—
B	A/C condenser fan relay	—	W30	—	0.5	ME221-C1-12	—	—	—
C	Starter input (12V while cranking)	—	W45	—	0.5	ME221-C1-7	—	—	—
E	Check engine light (MIL)	—	W34	—	0.5	ME221-C1-69	—	—	—
G	A/C clutch relay	—	W31	—	0.5	ME221-C1-74	—	—	—
K	A/C pressure switch (A/C request)	—	—	—	—	—	—	—	—
L	Clutch switch	—	—	—	—	—	—	—	—
M	Vehicle speed sensor (VSS)	—	W44	—	0.5	ME221-C1-6	—	—	—
Q	Brake switch	—	—	—	—	—	—	—	—
U	Fuel pump relay (low-side)	—	W32	—	0.5	ME221-C1-44	—	—	—

OEM-3

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
B	MAF sensor input	—	W26	—	0.5	ME221-C1-26	—	—	—
C	Front O2 sensor input	—	—	—	—	—	—	—	—
D	Rear O2 sensor input	—	—	—	—	—	—	—	—
F	Throttle position (TPS)	—	W27	—	0.5	ME221-C1-56	—	—	—
G	Engine coolant temp (CLT)	—	W28	—	0.5	ME221-C1-86	—	—	—
H	EGR boost sensor	—	W41	—	0.5	ME221-C1-17	—	—	—
I	+5V sensor reference	—	W16	—	0.5	ME221-C1-45	—	—	—
J	EGR valve position sensor	—	—	—	—	—	—	—	—
K	Intake air temp (IAT)	—	W43	—	0.5	ME221-C1-57	—	—	—
L	Idle switch (closed throttle)	—	—	—	—	—	—	—	—
M	Front O2 heater control	—	W33	—	0.5	ME221-C1-16	—	—	—
N	EGR boost sensor (2nd channel)	—	W42	—	0.5	ME221-C1-18	—	—	—
O	Sensor ground	—	W12	—	0.5	SP-0V-1	—	—	—
P	Power steering pressure switch	—	—	—	—	—	—	—	—

OEM-4

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
A	Chassis ground	—	W4	—	0.85	SP-GND-1	—	—	—
B	ECU power +12V (main relay)	—	W1	—	0.85	SP-14V-1	—	—	—
C	Chassis ground	—	W5	—	0.85	SP-GND-1	—	—	—
D	Chassis ground	—	W6	—	0.85	SP-GND-1	—	—	—
E	Crank position (CKP) sensor	—	W17	—	0.5	ME221-C1-80	—	—	—
F	CAS SGT (cam trigger)	—	W19	—	0.5	ME221-C1-23	—	—	—
G	CAS SGC (cam sync)	—	W18	—	0.5	ME221-C1-22	—	—	—
H	Crank pickup timing ground (CKP gnd)	—	W13	—	0.5	SP-0V-1	—	—	—
I	Permanent +12V (battery)	—	—	—	—	—	—	—	—
J	PRC solenoid (FPR control)	—	W35	—	0.5	ME221-C1-39	—	—	—
K	Chassis ground	—	W7	—	0.85	SP-GND-1	—	—	—
L	Tachometer output	—	W40	—	0.5	ME221-C1-79	—	—	—
N	Ignition coil trigger (cyl 1&4)	—	W20	—	0.5	ME221-C1-32	—	—	—
O	EGR vent solenoid	—	W36	—	0.5	ME221-C1-37	—	—	—
P	EGR vacuum solenoid	—	W37	—	0.5	ME221-C1-42	—	—	—
Q	Idle air control (IAC) valve	—	W38	—	0.5	ME221-C1-72	—	—	—
R	Ignition coil trigger (cyl 2&3)	—	W21	—	0.5	ME221-C1-31	—	—	—
T	EVAP purge solenoid	—	W39	—	0.5	ME221-C1-43	—	—	—
U	Injector 1 (cyl 1)	—	W22	—	0.5	ME221-C1-63	—	—	—
V	Injector 2 (cyl 2)	—	W23	—	0.5	ME221-C1-4	—	—	—
W	Injector 3 (cyl 3)	—	W24	—	0.5	ME221-C1-33	—	—	—
X	Injector 4 (cyl 4)	—	W25	—	0.5	ME221-C1-3	—	—	—

SP-0V

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	—	—	W12	—	0.5	OEM-3-O	—	—	—
1	—	—	W13	—	0.5	OEM-4-H	—	—	—
1	—	—	W14	—	0.5	ME221-C1-52	—	—	—
1	—	—	W15	—	0.5	ME221-C1-84	—	—	—

SP-14V

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	—	—	W1	—	0.85	OEM-4-B	—	—	—
1	—	—	W2	—	0.85	ME221-C1-15	—	—	—
1	—	—	W3	—	0.85	ME221-C1-64	—	—	—

SP-GND

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	—	—	W4	—	0.85	OEM-4-A	—	—	—
1	—	—	W5	—	0.85	OEM-4-C	—	—	—
1	—	—	W6	—	0.85	OEM-4-D	—	—	—
1	—	—	W7	—	0.85	OEM-4-K	—	—	—
1	—	—	W8	—	0.85	ME221-C1-10	—	—	—
1	—	—	W9	—	0.85	ME221-C1-61	—	—	—
1	—	—	W10	—	0.85	ME221-C1-89	—	—	—
1	—	—	W11	—	0.85	ME221-C1-90	—	—	—

Pin map

OEM point	OEM function	OEM family	Target point	Target function	Target family	Evidence
OEM-1-A	Cooling fan relay (low-side)	low_side_out	ME221-C1-73	LOW SIDE 1	low_side_out	corroborated
OEM-1-B	A/C condenser fan relay	low_side_out	ME221-C1-12	LOW SIDE 2	low_side_out	corroborated
OEM-1-C	Starter input (12V while cranking)	digital_in	ME221-C1-7	DIG_IN 2	digital_in	corroborated
OEM-1-E	Check engine light (MIL)	low_side_out	ME221-C1-69	LOW SIDE 5	low_side_out	corroborated
OEM-1-G	A/C clutch relay	low_side_out	ME221-C1-74	LOW SIDE 3	low_side_out	corroborated
OEM-1-K	A/C pressure switch (A/C request)	digital_in	—	—	—	corroborated
OEM-1-L	Clutch switch	digital_in	—	—	—	corroborated
OEM-1-M	Vehicle speed sensor (VSS)	digital_in	ME221-C1-6	DIG_IN 1	digital_in	corroborated
OEM-1-Q	Brake switch	digital_in	—	—	—	corroborated
OEM-1-U	Fuel pump relay (low-side)	low_side_out	ME221-C1-44	LOW SIDE 4	low_side_out	corroborated
OEM-3-B	MAF sensor input	analog_in	ME221-C1-26	ANA VOLT 1	analog_in	corroborated
OEM-3-C	Front O2 sensor input	lambda_nb_in	—	—	—	corroborated
OEM-3-D	Rear O2 sensor input	lambda_nb_in	—	—	—	corroborated
OEM-3-F	Throttle position (TPS)	analog_in	ME221-C1-56	ANA VOLT 2	analog_in	corroborated
OEM-3-G	Engine coolant temp (CLT)	temp_in	ME221-C1-86	ANA TEMP 1	temp_in	corroborated
OEM-3-H	EGR boost sensor	analog_in	ME221-C1-17	ANA VOLT 3	analog_in	corroborated
OEM-3-I	+5V sensor reference	vref	ME221-C1-45	5V REF	vref	corroborated
OEM-3-J	EGR valve position sensor	analog_in	—	—	—	corroborated
OEM-3-K	Intake air temp (IAT)	temp_in	ME221-C1-57	ANA TEMP 2	temp_in	corroborated
OEM-3-L	Idle switch (closed throttle)	digital_in	—	—	—	corroborated
OEM-3-M	Front O2 heater control	low_side_out	ME221-C1-16	LSU HEATER -VE	low_side_out	corroborated
OEM-3-N	EGR boost sensor (2nd channel)	analog_in	ME221-C1-18	ANA VOLT 4	analog_in	corroborated
OEM-3-O	Sensor ground	sensor_ground	ME221-C1-52 + ME221-C1-84	SENSORS GROUND + Sensor Ground	sensor_ground	corroborated
OEM-3-P	Power steering pressure switch	digital_in	—	—	—	corroborated
OEM-4-A	Chassis ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	corroborated
OEM-4-B	ECU power +12V (main relay)	power_in	ME221-C1-15 + ME221-C1-64	IGN +12V + VBAT	power_in	corroborated
OEM-4-C	Chassis ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	corroborated
OEM-4-D	Chassis ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	corroborated
OEM-4-E	Crank position (CKP) sensor	trigger_in	ME221-C1-80	CRANK VR+	trigger_in	corroborated
OEM-4-F	CAS SGT (cam trigger)	trigger_in	ME221-C1-23	CAM A VR-	trigger_in	corroborated
OEM-4-G	CAS SGC (cam sync)	trigger_in	ME221-C1-22	CAM A VR+	trigger_in	corroborated
OEM-4-H	Crank pickup timing ground (CKP gnd)	sensor_ground	ME221-C1-52 + ME221-C1-84	SENSORS GROUND + Sensor Ground	sensor_ground	corroborated
OEM-4-I	Permanent +12V (battery)	power_in	—	—	—	corroborated
OEM-4-J	PRC solenoid (FPR control)	low_side_out	ME221-C1-39	LOW SIDE 6	low_side_out	corroborated
OEM-4-K	Chassis ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	corroborated
OEM-4-L	Tachometer output	tacho_out	ME221-C1-79	TACHOMETER	tacho_out	corroborated
OEM-4-N	Ignition coil trigger (cyl 1&4)	ignition_out	ME221-C1-32	COIL 1	ignition_out	corroborated
OEM-4-O	EGR vent solenoid	low_side_out	ME221-C1-37	LOW SIDE RELAY 11	low_side_out	corroborated
OEM-4-P	EGR vacuum solenoid	low_side_out	ME221-C1-42	LOW SIDE RELAY 12	low_side_out	corroborated
OEM-4-Q	Idle air control (IAC) valve	low_side_out	ME221-C1-72	LOW SIDE RELAY 13	low_side_out	corroborated
OEM-4-R	Ignition coil trigger (cyl 2&3)	ignition_out	ME221-C1-31	COIL 2	ignition_out	corroborated
OEM-4-T	EVAP purge solenoid	low_side_out	ME221-C1-43	LOW SIDE RELAY 14	low_side_out	corroborated
OEM-4-U	Injector 1 (cyl 1)	injector_out	ME221-C1-63	INJECTOR 1	injector_out	corroborated
OEM-4-V	Injector 2 (cyl 2)	injector_out	ME221-C1-4	INJECTOR 2	injector_out	corroborated
OEM-4-W	Injector 3 (cyl 3)	injector_out	ME221-C1-33	INJECTOR 3	injector_out	corroborated
OEM-4-X	Injector 4 (cyl 4)	injector_out	ME221-C1-3	INJECTOR 4	injector_out	corroborated

Cut list

Wire	From	To	Gauge (mm²)	Length	Signal	Ident
W1	OEM-4-B	SP-14V-1	0.85	no route	ECU power +12V (main relay)	—
W2	SP-14V-1	ME221-C1-15	0.85	no route	IGN +12V	—
W3	SP-14V-1	ME221-C1-64	0.85	no route	VBAT	—
W4	OEM-4-A	SP-GND-1	0.85	no route	Chassis ground	—
W5	OEM-4-C	SP-GND-1	0.85	no route	Chassis ground	—
W6	OEM-4-D	SP-GND-1	0.85	no route	Chassis ground	—
W7	OEM-4-K	SP-GND-1	0.85	no route	Chassis ground	—
W8	SP-GND-1	ME221-C1-10	0.85	no route	GROUND CHASSIS	—
W9	SP-GND-1	ME221-C1-61	0.85	no route	GROUND	—
W10	SP-GND-1	ME221-C1-89	0.85	no route	GROUND	—
W11	SP-GND-1	ME221-C1-90	0.85	no route	GROUND	—
W12	OEM-3-O	SP-0V-1	0.5	no route	Sensor ground	—
W13	OEM-4-H	SP-0V-1	0.5	no route	Crank pickup timing ground (CKP gnd)	—
W14	SP-0V-1	ME221-C1-52	0.5	no route	SENSORS GROUND	—
W15	SP-0V-1	ME221-C1-84	0.5	no route	Sensor Ground	—
W16	OEM-3-I	ME221-C1-45	0.5	no route	+5V sensor reference	—
W17	OEM-4-E	ME221-C1-80	0.5	no route	Crank position (CKP) sensor	—
W18	OEM-4-G	ME221-C1-22	0.5	no route	CAS SGC (cam sync)	—
W19	OEM-4-F	ME221-C1-23	0.5	no route	CAS SGT (cam trigger)	—
W20	OEM-4-N	ME221-C1-32	0.5	no route	Ignition coil trigger (cyl 1&4)	—
W21	OEM-4-R	ME221-C1-31	0.5	no route	Ignition coil trigger (cyl 2&3)	—
W22	OEM-4-U	ME221-C1-63	0.5	no route	Injector 1 (cyl 1)	—
W23	OEM-4-V	ME221-C1-4	0.5	no route	Injector 2 (cyl 2)	—
W24	OEM-4-W	ME221-C1-33	0.5	no route	Injector 3 (cyl 3)	—
W25	OEM-4-X	ME221-C1-3	0.5	no route	Injector 4 (cyl 4)	—
W26	OEM-3-B	ME221-C1-26	0.5	no route	MAF sensor input	—
W27	OEM-3-F	ME221-C1-56	0.5	no route	Throttle position (TPS)	—
W28	OEM-3-G	ME221-C1-86	0.5	no route	Engine coolant temp (CLT)	—
W29	OEM-1-A	ME221-C1-73	0.5	no route	Cooling fan relay (low-side)	—
W30	OEM-1-B	ME221-C1-12	0.5	no route	A/C condenser fan relay	—
W31	OEM-1-G	ME221-C1-74	0.5	no route	A/C clutch relay	—
W32	OEM-1-U	ME221-C1-44	0.5	no route	Fuel pump relay (low-side)	—
W33	OEM-3-M	ME221-C1-16	0.5	no route	Front O2 heater control	—
W34	OEM-1-E	ME221-C1-69	0.5	no route	Check engine light (MIL)	—
W35	OEM-4-J	ME221-C1-39	0.5	no route	PRC solenoid (FPR control)	—
W36	OEM-4-O	ME221-C1-37	0.5	no route	EGR vent solenoid	—
W37	OEM-4-P	ME221-C1-42	0.5	no route	EGR vacuum solenoid	—
W38	OEM-4-Q	ME221-C1-72	0.5	no route	Idle air control (IAC) valve	—
W39	OEM-4-T	ME221-C1-43	0.5	no route	EVAP purge solenoid	—
W40	OEM-4-L	ME221-C1-79	0.5	no route	Tachometer output	—
W41	OEM-3-H	ME221-C1-17	0.5	no route	EGR boost sensor	—
W42	OEM-3-N	ME221-C1-18	0.5	no route	EGR boost sensor (2nd channel)	—
W43	OEM-3-K	ME221-C1-57	0.5	no route	Intake air temp (IAT)	—
W44	OEM-1-M	ME221-C1-6	0.5	no route	Vehicle speed sensor (VSS)	—
W45	OEM-1-C	ME221-C1-7	0.5	no route	Starter input (12V while cranking)	—

Bill of materials

Category	Part number	Manufacturer	Description	Qty	Unit

ECU setup sheet

Role	Engine ref	Engine signal	Sensor	ECU point	ECU function	ECU class	Setup flag
No configured channels.

Findings

Open (1)

Severity	Code	Subject	Message
info	UNMAPPED	OEM	8 optional OEM pins are not mapped: OEM-1-K A/C pressure switch (A/C request); OEM-1-L Clutch switch; OEM-1-Q Brake switch; OEM-3-C Front O2 sensor input; OEM-3-D Rear O2 sensor input; OEM-3-J EGR valve position sensor; OEM-3-L Idle switch (closed throttle); OEM-3-P Power steering pressure switch

Accepted (1)

Code	Subject	Reason	By
REQUIRED_UNMAPPED	OEM-4-I	Battery-constant (memory) feed of the stock ECU: the new ECU has no such input, so it is not needed.	mapping-proposal

Notes

Auto-mapped by auto_map() from the library pin data on 2026-10-11. Review every wire against both manuals before building. Not wired: - OEM-4 I: Permanent +12V (battery): Motorsport Electronics ME221 has no battery-constant input; not needed - OEM-3 C: Front O2 sensor input: no free o2_narrowband/analog_0_5 on Motorsport Electronics ME221 - OEM-3 D: Rear O2 sensor input: no free o2_narrowband/analog_0_5 on Motorsport Electronics ME221 - OEM-3 J: EGR valve position sensor: no free analog_0_5 on Motorsport Electronics ME221 - OEM-1 K: A/C pressure switch (A/C request): no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-1 L: Clutch switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-1 Q: Brake switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-3 L: Idle switch (closed throttle): no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-3 P: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221

Sources

Reliability	Kind	Title	URL	Archive	Captured	SHA-256
4	vendor_doc	AEM EMS 30-1720 Plug-and-Play adapter manual (1996-97 Miata)	https://static.summitracing.com/global/images/instructions/avm-30-1720.pdf	—	—	—
4	vendor_doc	Motorsport Electronics GEN2 ME221/ME360/ME442 wire-in pinout	https://motorsport-electronics.co.uk/onlinehelp/html/ME442ME360ME221GEN2Wire-InPinout.html	—	—	—
3	community_copy	Mellens.net: 1996 Mazda Miata wiring diagrams (FSM-derived)	http://www.mellens.net/mazda/mazda_miata_extra_manual/1996_wiring.pdf	—	—	—