i have a 2002 gv 3.3 v6 and the engine light came on when i started up this afternoon looked in handbook and says about loose caps? fuel quality? or servicing? help please

 

May be as simple as tightening your fuel fill tube cap or maybe not. You'll have to have the codes read with a scanner or you can cycle the key from off to on three times within 5 seconds, leaving it on and read the codes off your odometer.

 

i done that the codes i have are p168.5 p168.4 p013.5

 

got 3 codes p168.5 p168.4 p013.5

 

P0135 is related to O2 sensor heater circuit and is probably the cause of the light

 

how easy is it to replacement the part have searched it and says about lambda sensor on exhaust nearest to engine.

 

Not the greatest video but it will get you there eventually. This should have been a 2 minute video not 7+.
OBD-II Trouble Code: P0135 Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor1)

1685 = SKIM detected an invalid key