02 Sensor Harness Missing

The green/yellow wire is the 12 volts for the O2 sensor heater, the black/gray wire is the signal & heater power ground, other wire is the O2 sensor output. The sensor wiring is Teflon insulated to survive the high heat around the exhaust system. Use regular insulated wire on the O2 sensors and the heat from the exhaust will melt or damage the wire's insulation.


The numbers on the sensor body match the numbers on the sensor socket. That shows you what wires are the heater, ground and sensor outputs.

60 is the sensor and heater ground. It terminates up in the engine fuel injector harness with an orange wire that bolts to either the back of the cylinder head, intake manifold or car body. Make sure this is grounded if you want the O2 sensors to work correctly.

90 (dark brown/lt green)& 94 (dark green/Purple) are the O2 sensor outputs.

687 is the 12 volt O2 sensor heater power that connects to a fuse link in the wiring harness.







The diagram for the O2 sensor harness is below:
Diagram courtesy of Tmoss & Stang&2birds



See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.


Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 29