Stefan, on our 4.6L mod engines there are 4 heated oxygen sensors. 2 before the dual converters on the exhaust pipes, and 2 after. If your not getting any CE light, they should be fine. However, if you have reason to believe they are bad, here is how you check them out:
**Warning-Do not pierce the wires when testing heated oxygen sensors, as this can lead to wiring harness damage. Backprobe the connector to properly read the voltage of HO2S.
1. Disconnect the HO2S(Heated O2 Sensor)
2. Measure the resistance between PWR and GND terminals of the sensor. If the reading is approximately 6 ohms at 68 degrees Fahrenhiet, the sensor's heater element is in good condition.
3. With the HO2S connected and engine running, measure the voltage with a Digital Volt-Ohmmeter between terminals HO2S and SIG RTN(GND) of the oxygen sensor connector. If the voltage readings are approximately equal to those below, the sensor is okay.
Ignition ON, engine OFF- 0 Volts
Idle(cold)- 0 Volts
Idle(warm)- 0-1.0 Volts
Acceleration- 0.5-1.0 Volts
Decelaration- 0-0.5 Volts
Per Chiltons
Hope this helps!
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96' GT
5-speed,K&N air filter,removed air silencer,80mm MAF,Mac True Fit Cat-Back
http://minot.com/~topel/stang9.JPG