Looking for a quick reference guide to the OBD1 Engine Harness Pinout? This post provides an overview of the ECU A, B, and D connectors, along with the C101 chassis connectors. Whether you're troubleshooting, wiring up an engine swap, or simply need to verify pin locations, this guide serves as a handy resource. Stay tuned for more wiring guides and tech tips!

OEM OBD1 Honda ECU Pinout

1992-1995 Civic | 1992-1995 Integra

1	3	5	7	9	11	13	15	17	19	21	23	25
2	4	6	/	/	12	/	16	/	20	22	24	26

OBD1 ECU A (26 Pin) C404 Civic, C410 Integra
Pin	Wire Color	Terminal Name	Description	Test
1	BRN	INJ1	Injector 1	Ignition On: 12V, Engine running: (-) Pulses
2	YEL	INJ4	Injector 4	Ignition On: 12V, Engine running: (-) Pulses
3	RED	INJ2	Injector 2	Ignition On: 12V, Engine running: (-) Pulses
4	ORN/WHT (Civic) to GRN/YEL	VTS	VTEC SOLENOID VALVE	Low RPM: 0V, High RPM: 12V
5	LT BLU, BLU (Integra)	INJ3	Injector 3	Ignition On: 12V, Engine running: (-) Pulses
6	ORN/BLK	PO2SHTC	Primary O2 Sensor Heater Control	Ignition On: 12V, Operating Temperature: 0V
7	GRN/YEL (Civic), GRN/BLU (Integra)	FLR	Fuel Relay (Main Relay)	0V when activated, 12V resting
8	GRN/YEL (Civic), GRN/BLU (Integra)	FLR	Fuel Relay (Main Relay)	Redundant
9	GRN/WHT to BLU/YEL (Civic), BLK/BLU (Integra)	IACV	Idle Air Control Valve	Idle: 6 - 10V
11	ORN/BLU	EGR Control Solenoid	Drives EGR valve (VX)	On: Duty controlled, Off: 0V
12	YEL/GRN (Civic) to GRN (Integra)	FANC	Radiator Fan Switch	Fan Running: 0V
13	GRN/ORN	MIL	Malfunction Indicator Light	On: 0V, Off: 12V
15	BLK/RED	ACC	A/C Compressor Clutch	AC On: 0V, AC Off: 12V
16	WHT/YEL (Civic), WHT/GRN (Integra)	ALTC	Alternator Control	12 - 0V
17	PNK/BLU (GSR B18C1)	IAB SOL	Intake Air Bypass	Below 5750RPM: 12V
19	WHT	ICS	Intake Control Solenoid (H22A)
20	RED to RED/BLK to RED	PCS	Purge Control Solenoid	Coolant Temp > 154F: 12V when activated
21	RED/GRN (Civic) YEL/GRN (Integra)	ICM	Ignition Control Module	Key (III): 12V, Engine running: pulses
22	RED/GRN (Civic only)	ICM	Ignition Control Module (redundant)	Key (III): 12V, Engine running: pulses
23	BLK	PG1 (Main Relay, VTP SW, G101)	Power Ground 1	Less than 1V at all times
24	BLK	PG2 (Main Relay, VTP SW, G101)	Power Ground 2	Less than 1V at all times
25	YEL/BLK	IGP2	Ignition Power Ground 2, Main Relay, Junction, INJ	Key (II): 12V
26	BLK/RED (Civic), BRN/BLK (Integra)	LG1	Logic Ground 1	Less than 1V at all times

 

1	/	5	7	9	11	13	15
2	/	/	8	10	12	14	16

OBD1 ECU B (16 Pin) C405 Civic, C408 Integra
Pin	Wire Color	Terminal Name	Description	Test
1	YEL/BLK	IGP1	Ignition Power 1, Main Relay, Junction, INJ	Ignition On: 12V
2	BRN/BLK	LG2	Logic Ground 2	Less than 1V at all times
5	BLU/RED	AC Switch (ACS)	Detects AC switch	AC switch On: 0V, AC Switch Off: 12V
7	PNK/BLK	CLSW	Clutch Switch (VX)
8	BRN/RED (Civic), GRN (Integra)	PSP SW	Power Steering Pressure Switch	When steering: 12V
9	BLU/WHT	Starter Switch Signal (STS)	Detects starting, Main Relay	Engine cranking: 12V
10	YEL/BLU to YEL/WHT (Civic), ORN (Integra)	VSS	Vehicle Speed Sensor	Ignition on, Front wheels rotating: 0 - 5V cycles
11	ORN	CYP P	Cylinder Position (Power)	Engine running: Pulses
12	WHT	CYP M	Cylinder Position (Ground)
13	ORN/BLU	TDC P	Top Dead Center (Power)	Engine running: Pulses
14	WHT/BLU	TDC M	Top Dead Center (Ground)
15	BLU/GRN	CKP P	Crank Position (Power)	Engine running: Pulses
16	BLU/YEL	CKP M	Crank Position (Ground)

 

1	3	/	7	9	11	13	15	17	19	21
2	4	6	8	10	12	14	16	18	20	22

OBD1 ECU D (22 Pin) C405 Civic, C409 Integra
Pin	Wire Color	Terminal Name	Description	Test
1	WHT/BLU	VBU Voltage Backup	ECU Power source	12V
2	GRN/WHT	BKSW	Brake Switch signal	Brake pressed: 12V
3	RED/BLU	KS	Knock Sensor (GSR, Type R)	Knock present: pulses
3	BLU/YEL to WHT (Civic VX)	LAF LABEL	5-wire O2 Sensor (VX)	O2 Unplugged, jumpered to D22: .3 - 4.9V
4	BRN (Civic), BRN/WHT (Integra)	Service Check Signal (SCS)	Enables Diagnostic mode	Jumpered: 0V, Not jumpered: 5V or Battery voltage
6	ORN/BLU (Civic) to BLU/BLK	VTP SW (USDM)	VTEC Pressure Switch	VTEC ON: 12V
7	LT BLU	DLC	Data Link Connector
8	WHT/BLU (Civic VX)	LAF VS+	5-wire O2 Sensor (VX)	Jumpered to D22: > .5V
9	PNK to BLU (Civic), WHT/RED (Integra)	ALT F	Alternator FR Signal	Engine running: voltage dependent on electrical load
10	GRN/RED	ELD	Electric Load Detector	Parking Lights On, Idle: 2.5 - 3.5V, Headlights On: 1.5 - 2.5V
11	LT GRN to RED/BLU (Civic), RED/BLK (Integra)	TPS	Throttle Position Sensor	Fully Open: 4.8V, Closed: .5V
12	WHT/BLK	EGRL (VX)	Exhaust Gas Recirculation Valve Position	Idle: 1.2V
13	RED/WHT	ECT	Engine Coolant Temp	.1 - 4.8V
14	WHT (Civic), WHT/RED (Integra)	PHO2S	Primary Heated O2 Sensor Signal	Full throttle, Operating temperature > .6V, Decel > .4V
14	ORN/BLU (Civic VX)	LAF IP+	5-wire O2 (VX)
15	RED/YEL	IAT	Intake Air Temperature	.1 - 4.8V
16	BLU/GRN to ORN (Civic VX)	LAF IP-, VS-	5-wire O2 (VX)	Jumpered TO D22: > .5V
17	WHT (Civic) or WHT/YEL (Integra)	MAP	Manifold Absolute Pressure	Ignition on: 3V, Idle: ~1V
18	PNK/GRN to LT BLU	SIL	Upshift Light (CX, VX)
19	YEL/GRN (Civic) or YEL/WHT to YEL/RED (Integra)	VCC1	Sensor Voltage 1 (MAP)	Ignition on: 5V
20	YEL/WHT (Civic), YEL/BLU (Integra)	VCC2	Sensor Voltage 2 (TPS)	Ignition on: 5V
21	GRN/BLU (Civic) to GRN/WHT (Integra)	SG1	Sensor Ground 1	Less than 1V at all times
22	GRN/WHT (Civic), GRN/BLU (Integra)	SG2	Sensor Ground 2	Less than 1V at all times

 

O2 Sensors

 

MAP Sensor and TPS

1 2 3

 

MAP Sensor
Pin	Wire Color	Terminal Name	Description
1	WHT	MAP Signal	D17
2	GRN/WHT or GRN/BLU (D15B7)	SG1 Sensor Ground	D21
3	YEL/RED or YEL/GRN (D15B7)	VCC1 Sensor Voltage	D19

 

1 2 3

 

TPS
Pin	Wire Color	Terminal Name	Description
1	YEL/WHT	VCC2 Sensor Voltage	D20
2	RED/BLU	TPS Signal	D11
3	GRN/WHT	SG2 Sensor Ground	D22

Distributor

1	2	3	4
/	6	7	8

 

Distributor C107 Civic, C110 Integra
Pin	Wire Color	Terminal Name	Description
1	YEL/GRN	ICM	A21
2	BLU/GRN	CKP P	B15
3	ORN/BLU	TDC P	B13
4	ORN	CYL P	B11
6	BLU/YEL	CKP M	B16
7	WHT/BLU	TDC M	B14
8	WHT	CYP M	B12

 

Main Relay

1	2		3
4	5	6	7

 

Main Relay
Pin	Wire Color	Terminal Name	Description
1	GRN/YEL	FLR1, FLR2	A7, A8
2	BLU/WHT	STS	Under dash Fuse 18, B9
3	BLK	PG1, PG2	A23, A24, G101
4	YEL/GRN	FUEL PUMP
5	BLK/YEL	IG1	Under dash Fuse 12
6	YEL/BLK	IGP1, IGP2	A25, B1, INJ, O2
7	YEL/WHT	Constant 12V	Under hood ECU Fuse 31

 

Strut Tower Plugs

1 2 3
4	5	6	7
8	9	10	11
12 13 14

 

Driver-side round plug C304 / C126 Civic, C305 / C127 Integra
Pin	Wire Color	Terminal Name	Description
1	BLK/YEL	Alternator	From Alt to Dash Fuse
2	WHT/BLU	Battery Warning Light	Gauge Cluster to Alternator
3	RED to RED/BLK to RED	PCS	A20
3	PNK/BLU	IAB Solenoid	A17 B18C1
4	GRN/WHT to BLU/YEL, BLK/BLU (Integra)	IACV	A9
5	BLK/YEL	IG1 (Key) Alternator	Dash Fuse 24 to VSS, Main Relay, ELD
6	YEL/BLU to YEL/WHT, ORN (Integra)	VSS	B10
7	BLU (Integra)	Tachometer Engine Speed	ICM to Gauge Cluster
8	YEL/RED	Oil Warning Light	Gauge Cluster to Oil Pressure Sw
9	YEL/GRN, GRN (Integra)	FANC	A12, Radiator Fan Switch
10	BLK	PG2	A23, A24 to G101, VTP SW
11	YEL/GRN to GRN	Coolant Temp Sending Unit	Gauge Cluster
12	YEL, YEL/BLK (Integra)	IGP1 and 2 (AUTO)	B1 to INJ
13	GRN/BLK	LCB (AUTO)	A18
14	YEL/BLK, YEL (Integra)	LCA (AUTO)	A19

 

1 2 3
4	5	6	7
8 9 10

 

Passenger-side (10 Pin) round plug C222 / C102
Pin	Wire Color	Terminal Name	Description
1	BRN/BLK	LG 1 or 2	A26 or B2 Thermostat Housing
2	WHT/RED	PHO2S	D14
3	BRN/BLK	LG 1 or 2	A26 or B2 Thermostat Housing
4	ORN	CYP P	B11
5	WHT	CYP M	B12
6	ORN/BLU	TDC P	B13
7	WHT/BLU	TDC M	B14
8	BLU/GRN	CKP P	B15
9	BLU/YEL	CKP M	B16
10	RED/BLU	KS Knock Sensor	D3

 

1	2
3	4

 

Passenger-side C221 / C101
Pin	Wire Color	Terminal Name	Description
1	RED	INJ2	A3
2	BRN	INJ1	A1
3	YEL	INJ4	A2
4	BLU	INJ3	A5

 

1 2 3
4	5	6	7
8	9	10	11
12 13 14

 

Passenger-side (14 Pin) round plug C223 / C103
Pin	Wire Color	Terminal Name	Description
1	WHT/GRN	ALT C	A16
2	ORN/BLK	PO2SHTC	A6
3	GRN/YEL	VTS	A4 VTEC Solenoid
4	GRN/WHT	SG1 - MAP	D21
5	WHT/YEL	MAP	D17
6	YEL/WHT / YEL/RED	VCC1 to MAP	D19
7	BLU/BLK	VT PSW	D6 VTEC Pressure Switch
8	RED/BLK	TPS	D11
9	GRN/BLU - GRN/BLK	SG2 to PHO2S	D22
10	YEL/BLU	VCC2 to TPS	D20
11	YEL/GRN	ICM	A21
12	RED/YEL	IAT	D15
13	RED/WHT	ECT	D13
14	WHT/RED	ALT F	D9