Vehicle:Mazda Miata 2003

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See also

For power see

NB2 Miata ECU Connectors Drawing.png


Coil three wire plug:

middle wire GND

pin closer to the engine is +12v

pin further away from the engine signal

Plug 1 (ECU connector #2)

"rusEfi harness" does not mean much - that's just the way I bundle 4-5 wires together on my cars

pos color desc type rusEfi harness
2A Yellow/Black Injector #1 orange Y1
2B Red/Yellow Engine radiator fan orange B4
2C Blue/White AC radiator fan
2D Violet/Green Injector #2 blue Y1
2E Light Green EGR Valve #1 Coil
2F White/Green EGR Valve #2 Coil
2G Yellow/Red Injector #3 white Y1
2H Pink/Black EGR Valve #3 Coil
2I Pink EGR Valve #4 Coil
2J Yellow/Green Injector #4 green Y1
2K A/C Relay
2L NA Does not exist
2M Red/White Fuel Pump Relay red B4
2N VTCS Control
2P Orange IAC (positive) idle +12v wired to main relay via 4AF red, short wire
2Q Violet/Red IAC (negative) idle low-side with diode blue b4
2R White/Blue MIL Control low-side white Y1

Plug 2 (ECU Connector #3)

pos color desc type rusEfi harness
3A Black Injector GND ground black Y1
3B Black/Red PCM (ECU) GND ground black W4, sliced for MAP
3C Green/Yello Purge Control Solenoid
3D EGR Boost sens. sol.
3E CDCV Control (Evap canister?)
3F Brown/White Coil #1 (cylinder 1 & 4) white B4
3G NA Does not exist
3H Main relay control Low-side output white or red, R5
3I Black/Yellow Coil #2 (cylinder 2 & 3) orange B4
3J Black/Orange Front O2 sens. heater GND Presumably switched to GND in 'run'
3M Grey/Red Alternator field ctrl. PWM signal to control voltage orange R5
3O Green/Orange Tach OUT Drives tachometer green B4
3P White/Black Rear O2 sens. Signal
3Q Green/White K-Line (serial comm.) Probably goes to OBDII
3R NA Does not exist
3S Immobilizer comm.
3T VSS in blue W3
3U Alternator warn. light
3V Camshaft Sensor blue W3
3Y Crankshaft Sensor white W3

Plug 3 (ECU Connector #4)

pos color desc type rusEfi harness
4A Black/Blue GND ground black W4
4B Brake Switch
4C Power Steering Switch (Presumably used for 'Idle Up')
4D Yellow VVT Oil Control Valve pos. +12v wired to main relay via 4AF, short wire
4E DTM switching (Diagnostic Terminal?)
4F AC Pressure In
4G NA Does not exist
4H Neutral Switch
4I Clutch Switch
4J VTCS ca. switch
4L Lt GRN / RED Sensor +5V red W3, sliced for MAP
4M Knock sens. in white R5
4N IAT Sensor green B2
4O BLK / RED Sensor GND ground black B2
4P Red/Blue CLT Sensor blue B2
4Q NA Does not esist
4R Violet/Yellow VVT Oil Control Valve neg. low-side driver white B2
4S Black/White +12V engine fuse 15A ECU power source, run/start red B2
4T Alternator output voltage (seems to be feedback from alt.)
4U NC extra main relay for diode red, short wire
4V Green/Black TPS Sensor output green B2
4W Front O2 Sensor Signal
4X Pink MAF Sensor orange B2
4Y NA Does not exist
4Z Pink/Black ECU - TCM Communication for A/T
4AA Red Rear O2 Sensor
4AB FTP Sensor Fuel Tank Pressure
4AC ECU - TCM Communication for A/T
4AD Fuel Level Sensor
4AE EGR Boost Pressure Sensor
4AF white/Red +12v from main relay red, short wire
4AG Blue/Red Bat+ (Hot all times) 12v 10A fuse from battery
4AH Evap

desc type rusEfi harness
MAP signal analog blue
AFR signal analog white

Mazda miata 2003.png

Individual pages for printing: Mazda miata 2003 page 1.png

Mazda miata 2003 page 2.png

Mazda miata 2003 page 3.png

Automatic Transmission


Mazda miata 2003 at.png


NALDEC NC87 67 790 MAZDA MX5 EUNOS MK2 MK2.5 BURGLAR ALARM MODULE NC8767790 is not an immobilizer

US immobilizer 2001 miata immobilizer.png

Wiper Motor

2003 miata wiper motor.png


2003 miata charging.png

Air Conditioning

2003 miata ac.png

See also

Starting & power

In start or run ECU is powered from Engine Fuse 15A (behind left side of dash) via 4S. (This is different from 2002 - nothing on 4S in 2002)

ECU controls main relay via 3H. (This is different from 2002 - nothing on 3H in 2002)

ECU gets +12v from main relay output 4AF which is used as +12v source for VVT (4D) and IAC (2P).

Fly-back diode - stripe facing +12 - is needed between VVT 4D (power, stripe side) and VVT control 4R.

Fly-back diode - stripe facing +12 - is needed between IAC 2P (power, stripe side) and IAC control 2Q.


For ignition key see


Two timing marks - the left one is TDC