MX-5 Miata NB1 1999-00 (BP-4W) → Motorsport Electronics ME221 (auto)

MX-5 Miata NB1 1999-00 (BP-4W) — Motorsport Electronics — ME221

Drawn by Michael Gnankou · Rev 0 · proposal · 2026-10-09

Before you start

Status	proposal · not yet verified: nobody has reported building and running this harness
Open errors	none
Size of the job	44 wires · 7 connectors · 3 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-1-B	SP-14V-1	0.85	☐	☐	☐	☐	☐	☐	☐
W2	OEM-3-M	SP-14V-1	0.85	☐	☐	☐	☐	☐	☐	☐
W3	SP-14V-1	ME221-C1-14	0.85	☐	☐	☐	☐	☐	☐	☐
W4	SP-14V-1	ME221-C1-64	0.85	☐	☐	☐	☐	☐	☐	☐
W5	OEM-3-A	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W6	OEM-3-B	SP-GND-1	0.85	☐	☐	☐	☐	☐	☐	☐
W7	OEM-3-C	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-F	SP-0V-1	0.5	☐	☐	☐	☐	☐	☐	☐
W13	SP-0V-1	ME221-C1-52	0.5	☐	☐	☐	☐	☐	☐	☐
W14	SP-0V-1	ME221-C1-84	0.5	☐	☐	☐	☐	☐	☐	☐
W15	OEM-2-I	ME221-C1-45	0.5	☐	☐	☐	☐	☐	☐	☐
W16	OEM-2-J	ME221-C1-80	0.5	☐	☐	☐	☐	☐	☐	☐
W17	OEM-2-H	ME221-C1-22	0.5	☐	☐	☐	☐	☐	☐	☐
W18	OEM-2-F	ME221-C1-53	0.5	☐	☐	☐	☐	☐	☐	☐
W19	OEM-3-G	ME221-C1-32	0.5	☐	☐	☐	☐	☐	☐	☐
W20	OEM-3-H	ME221-C1-31	0.5	☐	☐	☐	☐	☐	☐	☐
W21	OEM-3-W	ME221-C1-63	0.5	☐	☐	☐	☐	☐	☐	☐
W22	OEM-3-X	ME221-C1-4	0.5	☐	☐	☐	☐	☐	☐	☐
W23	OEM-3-Y	ME221-C1-33	0.5	☐	☐	☐	☐	☐	☐	☐
W24	OEM-3-Z	ME221-C1-3	0.5	☐	☐	☐	☐	☐	☐	☐
W25	OEM-1-I	ME221-C1-73	0.5	☐	☐	☐	☐	☐	☐	☐
W26	OEM-1-R	ME221-C1-12	0.5	☐	☐	☐	☐	☐	☐	☐
W27	OEM-1-S	ME221-C1-74	0.5	☐	☐	☐	☐	☐	☐	☐
W28	OEM-3-N	ME221-C1-44	0.5	☐	☐	☐	☐	☐	☐	☐
W29	OEM-1-U	ME221-C1-16	0.5	☐	☐	☐	☐	☐	☐	☐
W30	OEM-3-V	ME221-C1-69	0.5	☐	☐	☐	☐	☐	☐	☐
W31	OEM-3-O	ME221-C1-39	0.5	☐	☐	☐	☐	☐	☐	☐
W32	OEM-1-E	ME221-C1-67	0.5	☐	☐	☐	☐	☐	☐	☐
W33	OEM-1-O	ME221-C1-68	0.5	☐	☐	☐	☐	☐	☐	☐
W34	OEM-1-Q	ME221-C1-70	0.5	☐	☐	☐	☐	☐	☐	☐
W35	OEM-2-M	ME221-C1-71	0.5	☐	☐	☐	☐	☐	☐	☐
W36	OEM-2-K	ME221-C1-79	0.5	☐	☐	☐	☐	☐	☐	☐
W37	OEM-2-L	ME221-C1-26	0.5	☐	☐	☐	☐	☐	☐	☐
W38	OEM-3-E	ME221-C1-56	0.5	☐	☐	☐	☐	☐	☐	☐
W39	OEM-2-C	ME221-C1-17	0.5	☐	☐	☐	☐	☐	☐	☐
W40	OEM-3-J	ME221-C1-18	0.5	☐	☐	☐	☐	☐	☐	☐
W41	OEM-2-E	ME221-C1-86	0.5	☐	☐	☐	☐	☐	☐	☐
W42	OEM-2-B	ME221-C1-57	0.5	☐	☐	☐	☐	☐	☐	☐
W43	OEM-2-D	ME221-C1-6	0.5	☐	☐	☐	☐	☐	☐	☐
W44	OEM-1-F	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-C1-14	ME221-C1-10	open (OL)	+12 V supply must not touch power ground
2	ME221-C1-14	ME221-C1-52	open (OL)	+12 V supply must not touch sensor ground
3	ME221-C1-45	ME221-C1-10	open (OL)	5 V sensor reference must not touch power ground
4	ME221-C1-45	ME221-C1-52	open (OL)	5 V sensor reference must not touch sensor ground
5	ME221-C1-14	ME221-C1-45	open (OL)	+12 V supply must not touch 5 V sensor reference

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	—	W26	—	0.5	OEM-1-R	—	—	—
14	VBAT IGNITION	—	W3	—	0.85	SP-14V-1	—	—	—
15	LSU HEATER +VE	—	—	—	—	—	—	—	—
16	LSU HEATER -VE	—	W29	—	0.5	OEM-1-U	—	—	—
17	ANA VOLT 3	—	W39	—	0.5	OEM-2-C	—	—	—
18	ANA VOLT 4	—	W40	—	0.5	OEM-3-J	—	—	—
19	LSU UN	—	—	—	—	—	—	—	—
2	COIL 3	—	—	—	—	—	—	—	—
20	LSU VM	—	—	—	—	—	—	—	—
21	CAN 1 HIGH	—	—	—	—	—	—	—	—
22	CAM A VR+	—	W17	—	0.5	OEM-2-H	—	—	—
23	CAM A VR-	—	—	—	—	—	—	—	—
24	SERIAL 1 GROUND	—	—	—	—	—	—	—	—
25	SERIAL 1 TX	—	—	—	—	—	—	—	—
26	ANA VOLT 1	—	W37	—	0.5	OEM-2-L	—	—	—
3	INJECTOR 4	—	W24	—	0.5	OEM-3-Z	—	—	—
31	COIL 2	—	W20	—	0.5	OEM-3-H	—	—	—
32	COIL 1	—	W19	—	0.5	OEM-3-G	—	—	—
33	INJECTOR 3	—	W23	—	0.5	OEM-3-Y	—	—	—
35	USB D+	—	—	—	—	—	—	—	—
36	USB D-	—	—	—	—	—	—	—	—
37	LOW SIDE RELAY 11	—	—	—	—	—	—	—	—
38	USB VBUS	—	—	—	—	—	—	—	—
39	LOW SIDE 6	—	W31	—	0.5	OEM-3-O	—	—	—
4	INJECTOR 2	—	W22	—	0.5	OEM-3-X	—	—	—
41	USB GROUND	—	—	—	—	—	—	—	—
42	LOW SIDE RELAY 12	—	—	—	—	—	—	—	—
43	LOW SIDE RELAY 14	—	—	—	—	—	—	—	—
44	LOW SIDE 4	—	W28	—	0.5	OEM-3-N	—	—	—
45	5V REF	—	W15	—	0.5	OEM-2-I	—	—	—
46	5V REF	—	—	—	—	—	—	—	—
49	LSU IA	—	—	—	—	—	—	—	—
50	LSU IP	—	—	—	—	—	—	—	—
51	CAN 1 LOW	—	—	—	—	—	—	—	—
52	SENSORS GROUND	—	W13	—	0.5	SP-0V-1	—	—	—
53	KNOCK 1 SIGNAL	—	W18	—	0.5	OEM-2-F	—	—	—
55	SERIAL 1 RX	—	—	—	—	—	—	—	—
56	ANA VOLT 2	—	W38	—	0.5	OEM-3-E	—	—	—
57	ANA TEMP 2	—	W42	—	0.5	OEM-2-B	—	—	—
6	DIG_IN 1	—	W43	—	0.5	OEM-2-D	—	—	—
61	GROUND	—	W9	—	0.85	SP-GND-1	—	—	—
63	INJECTOR 1	—	W21	—	0.5	OEM-3-W	—	—	—
64	VBAT	—	W4	—	0.85	SP-14V-1	—	—	—
67	Stepper 1 / A1	—	W32	—	0.5	OEM-1-E	—	—	—
68	Stepper 2 / A2	—	W33	—	0.5	OEM-1-O	—	—	—
69	LOW SIDE 5	—	W30	—	0.5	OEM-3-V	—	—	—
7	DIG_IN 2	—	W44	—	0.5	OEM-1-F	—	—	—
70	Stepper 3 / B1	—	W34	—	0.5	OEM-1-Q	—	—	—
71	Stepper 4 / B2	—	W35	—	0.5	OEM-2-M	—	—	—
72	LOW SIDE RELAY 13	—	—	—	—	—	—	—	—
73	LOW SIDE 1	—	W25	—	0.5	OEM-1-I	—	—	—
74	LOW SIDE 3	—	W27	—	0.5	OEM-1-S	—	—	—
76	5V REF	—	—	—	—	—	—	—	—
79	TACHOMETER	—	W36	—	0.5	OEM-2-K	—	—	—
80	CRANK VR+	—	W16	—	0.5	OEM-2-J	—	—	—
81	CRANK VR-	—	—	—	—	—	—	—	—
84	Sensor Ground	—	W14	—	0.5	SP-0V-1	—	—	—
86	ANA TEMP 1	—	W41	—	0.5	OEM-2-E	—	—	—
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	Constant +12V	—	—	—	—	—	—	—	—
B	ECU power +14V (main relay)	—	W1	—	0.85	SP-14V-1	—	—	—
E	Malfunction indicator lamp (MIL)	—	W32	—	0.5	ME221-C1-67	—	—	—
F	Brake switch	—	W44	—	0.5	ME221-C1-7	—	—	—
G	Power steering pressure switch	—	—	—	—	—	—	—	—
I	Condenser fan relay	—	W25	—	0.5	ME221-C1-73	—	—	—
O	Alternator control	—	W33	—	0.5	ME221-C1-68	—	—	—
P	A/C request	—	—	—	—	—	—	—	—
Q	Charge lamp	—	W34	—	0.5	ME221-C1-70	—	—	—
R	Cooling fan relay	—	W26	—	0.5	ME221-C1-12	—	—	—
S	A/C clutch relay	—	W27	—	0.5	ME221-C1-74	—	—	—
U	Front O2 heater	—	W29	—	0.5	ME221-C1-16	—	—	—
V	Neutral switch	—	—	—	—	—	—	—	—

OEM-2

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
A	Fuel tank pressure	—	—	—	—	—	—	—	—
B	Intake air temperature (IAT)	—	W42	—	0.5	ME221-C1-57	—	—	—
C	Front O2 signal	—	W39	—	0.5	ME221-C1-17	—	—	—
D	Vehicle speed	—	W43	—	0.5	ME221-C1-6	—	—	—
E	Coolant temperature (ECT)	—	W41	—	0.5	ME221-C1-86	—	—	—
F	Knock sensor	—	W18	—	0.5	ME221-C1-53	—	—	—
H	Cam position (CMP)	—	W17	—	0.5	ME221-C1-22	—	—	—
I	+5V sensor supply	—	W15	—	0.5	ME221-C1-45	—	—	—
J	Crank position (CKP)	—	W16	—	0.5	ME221-C1-80	—	—	—
K	Tachometer output	—	W36	—	0.5	ME221-C1-79	—	—	—
L	Mass air flow (MAF)	—	W37	—	0.5	ME221-C1-26	—	—	—
M	EGR valve	—	W35	—	0.5	ME221-C1-71	—	—	—
N	EGR valve	—	—	—	—	—	—	—	—
O	EGR valve	—	—	—	—	—	—	—	—
P	EGR valve	—	—	—	—	—	—	—	—

OEM-3

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
A	Power ground	—	W5	—	0.85	SP-GND-1	—	—	—
B	Power ground	—	W6	—	0.85	SP-GND-1	—	—	—
C	Power ground	—	W7	—	0.85	SP-GND-1	—	—	—
E	Throttle position (TPS)	—	W38	—	0.5	ME221-C1-56	—	—	—
F	Signal ground	—	W12	—	0.5	SP-0V-1	—	—	—
G	Ignition 1 (coils 1+4, wasted spark)	—	W19	—	0.5	ME221-C1-32	—	—	—
H	Ignition 2 (coils 2+3, wasted spark)	—	W20	—	0.5	ME221-C1-31	—	—	—
I	Clutch switch	—	—	—	—	—	—	—	—
J	Rear O2 signal	—	W40	—	0.5	ME221-C1-18	—	—	—
K	Fuel level	—	—	—	—	—	—	—	—
L	Evap purge solenoid	—	—	—	—	—	—	—	—
M	ISC valve +14V feed	—	W2	—	0.85	SP-14V-1	—	—	—
N	Fuel pump relay	—	W28	—	0.5	ME221-C1-44	—	—	—
O	ISC valve low side	—	W31	—	0.5	ME221-C1-39	—	—	—
Q	VICS solenoid (intake butterflies)	—	—	—	—	—	—	—	—
S	EGR boost sensor	—	—	—	—	—	—	—	—
T	EGR boost solenoid	—	—	—	—	—	—	—	—
U	Canister drain cut valve (CDCV)	—	—	—	—	—	—	—	—
V	Rear O2 heater	—	W30	—	0.5	ME221-C1-69	—	—	—
W	Injector 1	—	W21	—	0.5	ME221-C1-63	—	—	—
X	Injector 2	—	W22	—	0.5	ME221-C1-4	—	—	—
Y	Injector 3	—	W23	—	0.5	ME221-C1-33	—	—	—
Z	Injector 4	—	W24	—	0.5	ME221-C1-3	—	—	—

SP-0V

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

SP-14V

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	—	—	W1	—	0.85	OEM-1-B	—	—	—
1	—	—	W2	—	0.85	OEM-3-M	—	—	—
1	—	—	W3	—	0.85	ME221-C1-14	—	—	—
1	—	—	W4	—	0.85	ME221-C1-64	—	—	—

SP-GND

Cavity	Function	Signal	Wire	Colour	Gauge (mm²)	Destination	Terminal	Seal	Plug
1	—	—	W5	—	0.85	OEM-3-A	—	—	—
1	—	—	W6	—	0.85	OEM-3-B	—	—	—
1	—	—	W7	—	0.85	OEM-3-C	—	—	—
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	Constant +12V	power_in	—	—	—	single_source
OEM-1-B	ECU power +14V (main relay)	power_in	ME221-C1-14 + ME221-C1-64	VBAT IGNITION + VBAT	power_in	single_source
OEM-1-E	Malfunction indicator lamp (MIL)	low_side_out	ME221-C1-67	Stepper 1 / A1	hbridge_out	single_source
OEM-1-F	Brake switch	digital_in	ME221-C1-7	DIG_IN 2	digital_in	single_source
OEM-1-G	Power steering pressure switch	digital_in	—	—	—	single_source
OEM-1-I	Condenser fan relay	low_side_out	ME221-C1-73	LOW SIDE 1	low_side_out	single_source
OEM-1-O	Alternator control	low_side_out	ME221-C1-68	Stepper 2 / A2	hbridge_out	single_source
OEM-1-P	A/C request	digital_in	—	—	—	single_source
OEM-1-Q	Charge lamp	low_side_out	ME221-C1-70	Stepper 3 / B1	hbridge_out	single_source
OEM-1-R	Cooling fan relay	low_side_out	ME221-C1-12	LOW SIDE 2	low_side_out	single_source
OEM-1-S	A/C clutch relay	low_side_out	ME221-C1-74	LOW SIDE 3	low_side_out	single_source
OEM-1-U	Front O2 heater	low_side_out	ME221-C1-16	LSU HEATER -VE	low_side_out	single_source
OEM-1-V	Neutral switch	digital_in	—	—	—	single_source
OEM-2-A	Fuel tank pressure	analog_in	—	—	—	single_source
OEM-2-B	Intake air temperature (IAT)	temp_in	ME221-C1-57	ANA TEMP 2	temp_in	single_source
OEM-2-C	Front O2 signal	lambda_nb_in	ME221-C1-17	ANA VOLT 3	analog_in	single_source
OEM-2-D	Vehicle speed	digital_in	ME221-C1-6	DIG_IN 1	digital_in	single_source
OEM-2-E	Coolant temperature (ECT)	temp_in	ME221-C1-86	ANA TEMP 1	temp_in	single_source
OEM-2-F	Knock sensor	knock_in	ME221-C1-53	KNOCK 1 SIGNAL	knock_in	single_source
OEM-2-H	Cam position (CMP)	trigger_in	ME221-C1-22	CAM A VR+	trigger_in	single_source
OEM-2-I	+5V sensor supply	vref	ME221-C1-45	5V REF	vref	single_source
OEM-2-J	Crank position (CKP)	trigger_in	ME221-C1-80	CRANK VR+	trigger_in	single_source
OEM-2-K	Tachometer output	tacho_out	ME221-C1-79	TACHOMETER	tacho_out	single_source
OEM-2-L	Mass air flow (MAF)	analog_in	ME221-C1-26	ANA VOLT 1	analog_in	single_source
OEM-2-M	EGR valve	low_side_out	ME221-C1-71	Stepper 4 / B2	hbridge_out	single_source
OEM-2-N	EGR valve	low_side_out	—	—	—	single_source
OEM-2-O	EGR valve	low_side_out	—	—	—	single_source
OEM-2-P	EGR valve	low_side_out	—	—	—	single_source
OEM-3-A	Power ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	single_source
OEM-3-B	Power ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	single_source
OEM-3-C	Power ground	ground	ME221-C1-10 + ME221-C1-61 + ME221-C1-89 + ME221-C1-90	GROUND CHASSIS + GROUND + GROUND + GROUND	ground	single_source
OEM-3-E	Throttle position (TPS)	analog_in	ME221-C1-56	ANA VOLT 2	analog_in	single_source
OEM-3-F	Signal ground	sensor_ground	ME221-C1-52 + ME221-C1-84	SENSORS GROUND + Sensor Ground	sensor_ground	single_source
OEM-3-G	Ignition 1 (coils 1+4, wasted spark)	ignition_out	ME221-C1-32	COIL 1	ignition_out	single_source
OEM-3-H	Ignition 2 (coils 2+3, wasted spark)	ignition_out	ME221-C1-31	COIL 2	ignition_out	single_source
OEM-3-I	Clutch switch	digital_in	—	—	—	single_source
OEM-3-J	Rear O2 signal	lambda_nb_in	ME221-C1-18	ANA VOLT 4	analog_in	single_source
OEM-3-K	Fuel level	analog_in	—	—	—	single_source
OEM-3-L	Evap purge solenoid	low_side_out	—	—	—	single_source
OEM-3-M	ISC valve +14V feed	power_in	ME221-C1-14 + ME221-C1-64	VBAT IGNITION + VBAT	power_in	single_source
OEM-3-N	Fuel pump relay	low_side_out	ME221-C1-44	LOW SIDE 4	low_side_out	single_source
OEM-3-O	ISC valve low side	low_side_out	ME221-C1-39	LOW SIDE 6	low_side_out	single_source
OEM-3-Q	VICS solenoid (intake butterflies)	low_side_out	—	—	—	single_source
OEM-3-S	EGR boost sensor	analog_in	—	—	—	single_source
OEM-3-T	EGR boost solenoid	low_side_out	—	—	—	single_source
OEM-3-U	Canister drain cut valve (CDCV)	low_side_out	—	—	—	single_source
OEM-3-V	Rear O2 heater	low_side_out	ME221-C1-69	LOW SIDE 5	low_side_out	single_source
OEM-3-W	Injector 1	injector_out	ME221-C1-63	INJECTOR 1	injector_out	single_source
OEM-3-X	Injector 2	injector_out	ME221-C1-4	INJECTOR 2	injector_out	single_source
OEM-3-Y	Injector 3	injector_out	ME221-C1-33	INJECTOR 3	injector_out	single_source
OEM-3-Z	Injector 4	injector_out	ME221-C1-3	INJECTOR 4	injector_out	single_source

Cut list

Wire	From	To	Gauge (mm²)	Length	Signal	Ident
W1	OEM-1-B	SP-14V-1	0.85	no route	ECU power +14V (main relay)	—
W2	OEM-3-M	SP-14V-1	0.85	no route	ISC valve +14V feed	—
W3	SP-14V-1	ME221-C1-14	0.85	no route	VBAT IGNITION	—
W4	SP-14V-1	ME221-C1-64	0.85	no route	VBAT	—
W5	OEM-3-A	SP-GND-1	0.85	no route	Power ground	—
W6	OEM-3-B	SP-GND-1	0.85	no route	Power ground	—
W7	OEM-3-C	SP-GND-1	0.85	no route	Power 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-F	SP-0V-1	0.5	no route	Signal ground	—
W13	SP-0V-1	ME221-C1-52	0.5	no route	SENSORS GROUND	—
W14	SP-0V-1	ME221-C1-84	0.5	no route	Sensor Ground	—
W15	OEM-2-I	ME221-C1-45	0.5	no route	+5V sensor supply	—
W16	OEM-2-J	ME221-C1-80	0.5	no route	Crank position (CKP)	—
W17	OEM-2-H	ME221-C1-22	0.5	no route	Cam position (CMP)	—
W18	OEM-2-F	ME221-C1-53	0.5	no route	Knock sensor	—
W19	OEM-3-G	ME221-C1-32	0.5	no route	Ignition 1 (coils 1+4, wasted spark)	—
W20	OEM-3-H	ME221-C1-31	0.5	no route	Ignition 2 (coils 2+3, wasted spark)	—
W21	OEM-3-W	ME221-C1-63	0.5	no route	Injector 1	—
W22	OEM-3-X	ME221-C1-4	0.5	no route	Injector 2	—
W23	OEM-3-Y	ME221-C1-33	0.5	no route	Injector 3	—
W24	OEM-3-Z	ME221-C1-3	0.5	no route	Injector 4	—
W25	OEM-1-I	ME221-C1-73	0.5	no route	Condenser fan relay	—
W26	OEM-1-R	ME221-C1-12	0.5	no route	Cooling fan relay	—
W27	OEM-1-S	ME221-C1-74	0.5	no route	A/C clutch relay	—
W28	OEM-3-N	ME221-C1-44	0.5	no route	Fuel pump relay	—
W29	OEM-1-U	ME221-C1-16	0.5	no route	Front O2 heater	—
W30	OEM-3-V	ME221-C1-69	0.5	no route	Rear O2 heater	—
W31	OEM-3-O	ME221-C1-39	0.5	no route	ISC valve low side	—
W32	OEM-1-E	ME221-C1-67	0.5	no route	Malfunction indicator lamp (MIL)	—
W33	OEM-1-O	ME221-C1-68	0.5	no route	Alternator control	—
W34	OEM-1-Q	ME221-C1-70	0.5	no route	Charge lamp	—
W35	OEM-2-M	ME221-C1-71	0.5	no route	EGR valve	—
W36	OEM-2-K	ME221-C1-79	0.5	no route	Tachometer output	—
W37	OEM-2-L	ME221-C1-26	0.5	no route	Mass air flow (MAF)	—
W38	OEM-3-E	ME221-C1-56	0.5	no route	Throttle position (TPS)	—
W39	OEM-2-C	ME221-C1-17	0.5	no route	Front O2 signal	—
W40	OEM-3-J	ME221-C1-18	0.5	no route	Rear O2 signal	—
W41	OEM-2-E	ME221-C1-86	0.5	no route	Coolant temperature (ECT)	—
W42	OEM-2-B	ME221-C1-57	0.5	no route	Intake air temperature (IAT)	—
W43	OEM-2-D	ME221-C1-6	0.5	no route	Vehicle speed	—
W44	OEM-1-F	ME221-C1-7	0.5	no route	Brake switch	—

Bill of materials

Category	Part number	Manufacturer	Description	Qty	Unit
connector	174514-6	TE	AMP Multilock .040/.070 hybrid 16-pin female harness plug (Miata NB1 ECU)	1.000	ea
connector	174515-6	TE	AMP Multilock .040/.070 hybrid 22-pin female harness plug (Miata NA/NB ECU)	1.000	ea
connector	174516-6	TE	AMP Multilock .040/.070 hybrid 26-pin female harness plug (Miata NA/NB ECU)	1.000	ea

ECU setup sheet

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

Findings

Open (5)

Severity	Code	Subject	Message
warn	NET_FAMILY	OEM-1-E ↔ ME221-C1-67	OEM-1-E "Malfunction indicator lamp (MIL)" [low_side_out] is wired to ME221-C1-67 "Stepper 1 / A1" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way.
warn	NET_FAMILY	OEM-1-O ↔ ME221-C1-68	OEM-1-O "Alternator control" [low_side_out] is wired to ME221-C1-68 "Stepper 2 / A2" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way.
warn	NET_FAMILY	OEM-1-Q ↔ ME221-C1-70	OEM-1-Q "Charge lamp" [low_side_out] is wired to ME221-C1-70 "Stepper 3 / B1" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way.
warn	NET_FAMILY	OEM-2-M ↔ ME221-C1-71	OEM-2-M "EGR valve" [low_side_out] is wired to ME221-C1-71 "Stepper 4 / B2" [hbridge_out]. A half-bridge can act as a low-side switch only if configured that way.
info	UNMAPPED	OEM	14 optional OEM pins are not mapped: OEM-1-G Power steering pressure switch; OEM-1-P A/C request; OEM-1-V Neutral switch; OEM-2-A Fuel tank pressure; OEM-2-N EGR valve; OEM-2-O EGR valve; OEM-2-P EGR valve; OEM-3-I Clutch switch; OEM-3-K Fuel level; OEM-3-L Evap purge solenoid; OEM-3-Q VICS solenoid (intake butterflies); OEM-3-S EGR boost sensor; OEM-3-T EGR boost solenoid; OEM-3-U Canister drain cut valve (CDCV)

Accepted (1)

Code	Subject	Reason	By
REQUIRED_UNMAPPED	OEM-1-A	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 2026-10-08. Review every wire against both manuals before building. Not wired: - OEM-1 A: Constant +12V: Motorsport Electronics ME221 has no battery-constant input; not needed - OEM-2 N: EGR valve: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-2 O: EGR valve: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-2 P: EGR valve: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 L: Evap purge solenoid: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 Q: VICS solenoid (intake butterflies): no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 T: EGR boost solenoid: no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-3 U: Canister drain cut valve (CDCV): no free low_side/ls_hs/injector/hbridge on Motorsport Electronics ME221 - OEM-2 A: Fuel tank pressure: no free analog_0_5 on Motorsport Electronics ME221 - OEM-3 K: Fuel level: no free analog_0_5 on Motorsport Electronics ME221 - OEM-3 S: EGR boost sensor: no free analog_0_5 on Motorsport Electronics ME221 - OEM-1 G: Power steering pressure switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-1 P: A/C request: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-1 V: Neutral switch: no free switch_in/frequency_in/analog_0_5 on Motorsport Electronics ME221 - OEM-3 I: Clutch 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	Link G4X MX5NB1X install manual (NB1 1999-00)	https://linkecu.com/documentation/MX5XNB1.pdf	archive	2026-10-05	2e36c91270cc
4	vendor_doc	Motorsport Electronics GEN2 ME221/ME360/ME442 wire-in pinout	https://motorsport-electronics.co.uk/onlinehelp/html/ME442ME360ME221GEN2Wire-InPinout.html	—	—	—