where is the o2 sensor--i have one that a diagnostic says needs to be repleaced

there is no code for this. the code only tells you the failed system,not a bad part. they rarely go bad. it is usually something else that causes the o2 code. what code did you have?? by the way, there are 2 upstream just below the exhaust manifold and one downstream behind the cat. Roy

There are many diagnostic code pertaining to the Oxygen Sensor. P-0131 1/1 O2 SENSOR SHORTED TO GROUND, P-0132 1/1 O2 SENSOR SHORTED TO VOLTAGE, P-0133 1/1 O2 SENSOR SLOW RESPONSE, P-0135 1/1 O2 SENSOR HEATER FAILURE, P-0137 1/2 O2 SENSOR SHORTED TO GROUND, P-0138 1/2 O2 SENSOR SHORTED TO VOLTAGE, P-0139 1/2 OXYGEN SENSOR SLOW RESPONSE, P-0141 1/2 O2 SENSOR HEATER FAILURE. Some of the above codes will require O2 sensor replacement while others will need further diagnosis. For your reference 1/1 pertains to the upstream senor, which may be located on the front of the converter of pipe between the engine and converter, 1/2 is downstream located on the pipe after the converter. O2 heater related codes are EMISSION related codes for cold engine starts and do not affect engine performance, however for passing an Emission test, the sensor will have to be replaced.

ITS UNDER THE TRUCK ON THE MANIFOLD I CHANCED MINE ITS EASY IT COST 70 DALLARS THERE ARE TWO ONE BYE THE UP BYE THE MOTER AND ONE BEFORE THE MANAFOLD UNPLUGE IT AND TAKE IT OUT AND PUT IT BACK IN THIN HAVE AUTO ZONE USE THERE COPUTER AND RESEAT IT THE LIGHT WILL GO OFF