Basic electrical question regarding reverse lights.

[bikerjosh]

Been fixing a lot of little electrical lapses with Montero lately.
Working on trying to figure out why only one reverse light works.
Tried multiple bulbs, no difference.
When I put the car in reverse and put a test light probe in the socket and attach the other side to the chassis I get a completed circuit, so I figured ground was bad. Ran a jumper from the ground wire out of the socket to the chassis but still no luck. \
Feels like I am missing something here?
Any ideas?
thanks

 

[bikerjosh]

Put a multi meter on the circuit but I'm only getting 11.4 volts, shouldn't it light at least a little bit?

 

[mapper]

Corroded or bent contacts in the socket seems the only real likely possibility. Your test light was able to get a decent connection but the actual bulb can't connect clean to socket. That's all I can offer.