Drivers side tail light is not working. I have tried 2 new light bulbs and tested all connections and it has voltage. What could it be?

First make sure you have voltage at the tail light connection. If you do then check to make sure you have a good ground. Make sure the connections are clean. Check to see if the bulb is bad. It might have a bad connection. If no power at tail light then follow the wire to see if there is a bad spot in it.

https://www.cruzetalk.com/threads/cruze-wiring-diagrams.86769/

Voltage drop test the circuit to find the unwanted high resistance ! lose or bad connection in the circuit . How And Why To Perform Voltage Drop Test Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia

IF both lights are out most likely a fuse, check the drivers manual for location of fuse, check both sides of the fuse with a test light, must be voltage both sides, no voltage , cable from light switch to fuse faulty. voltage to only one side of fuse, fuse faulty. voltage to both side of fuse , cable to tail lights faulty, bulbs faulty or bad earth to tail lights.

check the connections and the ground wire (just trace the wires out)

I don't know if there is a relay but the head light switch controls the taillights You can check the auto parts store and see if they have a listing for a taillight relay otherwise You will need an electrical tester or test light. First connect one side of the test light or meter to a good ground.Take the probe of the test light and test the fuse on both sides and make sure it lights. If it is good on both sides try testing for voltage at the tail light sockets With the light switch turned on, If you have voltage at the socket you could be missing the ground to the tail light bulbs.or you could have bad bulbs or corroded sockets.An other possibility if no voltage is at the sockets you could have a defective headlight switch.Beyond that you will need a factory service manual with wiring diagrams or a detailed manual such as Mitchel's or one from Alldata

Check wiring with a test light or volt meter. switch lights to low beam, connect volt meter N probe to a good ground then probe the light socket for the low beam power cable, should show battery voltage, now switch to high beam and test for battery voltage if ok remove the grounded meter probe and probe the cable in the socket that you have not tested this is the ground cable, battery voltage should show if ground cable is ok. If no voltage repair cable ,If voltage present check filament on bulb high beam perhaps the new bulb is faulty.

The tail light circuit is separate from the brake and turn signal circuit. Either the bulb socket has gone bad or a wire has flaked out. Check for voltage at the socket on either pin base when you have your parking lights on. If voltage is present, it is either a worn socket failing to hold the bulb properly, or another bad bulb. If no voltage, determine which wire on the other side is tail light power, and run a new wire across to the side that isn't working and connect it to provide power.

Voltage drop test the electrical circuit .

Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia
Do you know what a wiring diagram is ? Do use a test light ,use a DMM - digital multi-meter . Free wiring diagram here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model . Under system click on lighting then under subsystem click on turn signal lamps . Then click the search button then the blue link . Scroll down to last diagram .

you need new bulbs in tail lights one bulb in each side has two elements one works brake other works running lights the elements in the bulb for tail lites are bad . so just replace bulbs. hope this helps.

carefuly test the socket that the light plugs into with a test light. I have seen alot of the newer pickups etc. that have the push in style lights have bad boards. cost like 19.00 at orielys. on the back of your tail lights when you take them off of the rig. do you have to unplug a wiring harness and take 2 screws out? and pull the black plastic peice out and the lights push in. that is the board i am talking about replacing. use the test light to check the plugend if it works that will tell you.