Oxygen Sensor Wiring Reference

1987-1989 Speed Density Truck
3-wire HEGO (Single)
HEGO SIG at EEC Pin #29
HEGO GND at Sensor body

1990-1995 Speed Density Truck
4-wire HEGO (Single)
HEGO SIG at EEC Pin #29
HEGO GND at EEC Pin #49

1994-1995 5.0L Mass Air Truck
4-wire HEGO (Single)
HEGO SIG at EEC Pin #44
HEGO GND at EEC Pin #46 (SIG RTN)

1995 5.8L Mass Air Truck
4-wire HEGO (Stereo)
L-HEGO SIG at EEC Pin #43
R-HEGO SIG at EEC Pin #44
HEGO GND at EEC Pin #46 (SIG RTN)

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1987 5.0L Speed Density Mustang
3-wire HEGO (Stereo)
L HEGO SIG at EEC Pin #43
R HEGO SIG at EEC Pin #29
HEGO GND at Sensor body

1988-1993 5.0L Mass Air Mustang
3-wire HEGO (Stereo)
L HEGO SIG at EEC Pin #43
R HEGO SIG at EEC Pin #29
HEGO GND at Sensor body

1994-1995 5.0L Mass Air Mustang
4-wire HEGO (Stereo)
L-HEGO SIG at EEC Pin #43
R-HEGO SIG at EEC Pin #44
HEGO GND at EEC Pin #46 (SIG RTN)





MAF Upgrade Notes:

• You can use a 3-wire HEGO in a 4-wire Harness Connector.

• You cannot use a 4-wire HEGO in a 3-wire Harness Connector.

• When using the A9L/A9P Mustang PCM, use stereo 3-wire HEGOs.

• When using the WAY1/VEX1/AKCO PCM, use a single 4-wire HEGO.

• When using the BIO0 PCM, use stereo 4-wire HEGOs.

HEGO Sensor Connector




HEGO 4-wire Sensor Connector




HEGO 3-wire Harness Connector




HEGO 4-wire Harness Connector




Speed Density 3-Wire Single HEGO (Before 1990)

12v PWR - P/O from Relay/Fuse Panel
12v GND - BK to G-101

HEGO SIG - DG/P from EEC Pin #29
SIG RTN - GND at Sensor body



Speed Density 4-Wire Single HEGO (1990+)

12v PWR - P/O from Relay/Fuse Panel
12v GND - BK to G-101

HEGO SIG - GY/LB from EEC Pin #29
SIG RTN - O to EEC Pin #49



MAF Stereo 3-Wire HEGO (A9L/A9P)

12v PWR - GY/Y from Relay/Fuse Panel
R 12v GND - BK/W to Body GND

R HEGO SIG - GY/LB from EEC Pin #29
SIG RTN - GND at Sensor body

12v PWR - GY/Y from Relay/Fuse Panel
L 12v GND - BK/W to Body GND

L HEGO SIG - R/BK from EEC Pin #43
SIG RTN - GND at Sensor body



MAF Single 4-Wire HEGO (WAY1/VEX1/AKCO)

12v PWR - P/O from Relay/Fuse Panel
12v GND - BK to G-101

HEGO SIG - GY/LB from EEC Pin #44
SIG RTN - GY/R to EEC Pin #46



MAF Stereo 4-Wire HEGO (BIO0)

12v PWR - P/O from Relay/Fuse Panel
R 12v GND - BK to G-101

R HEGO SIG - GY/LB from EEC Pin #44
SIG RTN - GY/R to EEC Pin #46

12v PWR - P/O from Relay/Fuse Panel
L 12v GND - BK to G-100

L HEGO SIG - R/BK from EEC Pin #43
SIG RTN - GY/R to EEC Pin #46