Actually one of the LED is just plain missing from the circuit board but otherwise all test good and light up using multimeter diode function.
Does it mean solder joints are bad and needs to be cleaned or re-done?
Most LED's in cars are 'jumbo" 10mm LED's.
A single led requires about 3.1 volts across it (out of circuit of course) and about 20 mA of current. Longer lead is positive and shorter lead is negative.
Depends on the LED, but the standard ones that have been around for 45 or so years are around that voltage. Newer surface mount LEDs (fairly common in replacement bulbs) are often less than that.
We used LEDs like these back in our breadboard projects. They would just plug right in, but often we would trim them do they didn't stick out so much. I tried driving it straight from a TTL output, but there were some buffers and TTL that was meant for driving LEDs. I forgot what those were called.
Surface mount is going to be a huge pain to desolder and resolder. They're usually baked in ovens to get the solder to flow. I recall when my company would pay to have someone do rework on a prototype board.Right some are SMD (Surface Mount devices) and not seeing the LED board in question it sounded as if he could de-solder the LED, a "through hole" LED which means it has long leads as in your picture above.