What does "Battery is good" mean? Did you do a load test, was it recently replaced... etc? Just because you're getting 12+v at the terminals doesn't mean you have the amps and remaining juice to actually start the car. On my original Hyundai battery which I replaced a few months ago, everything was great until one day one of the cells decided to start going. Voltage was good but you test it for load and it would fail. Measure voltage when you're trying to turn over . Ground and starter come to mind too along with Neutral Switch at the transmission. Can you try starting in Neutral?Turn the key on, dash lights turn on. Turn the key to start, all lights turn off, everything is dead. Battery is good. Any ideas?
These are symptoms of a high resistance, usually caused by a corroded/loose connection. As flemmons suggested, voltage drop testing is the way you diagnose the cause. I think it's more likely to be a body ground issue though, rather than the engine ground. You'd want to measure the voltage between the battery neg post and clean metal on the car body. The lower the voltage the better and >1V is defo a problem.Turn the key to start, all lights turn off, everything is dead.
Turn the key on, dash lights turn on. Turn the key to start, all lights turn off, everything is dead. Battery is good. Any ideas?
OP's original statement tends to rule out those suggestions regardless of year. More indicative of what AUTOSPARK and Login:LordByron are indicating. I would also have my battery tested for sure (or have it hooked up to a jump) to make sure I didn't get a battery with a bad cell.Two other suggestions as I don't know the year, check that the car is in Park as Sonata's have issues with the shifter. Second, check the brake switch under the pedal. Both of these items have been recalled.
If the battery is new I would think it was replaced because of a previous battery not operating correctly. If the alternator isn't charging the battery properly it won't let the car start. Being a new battery there should be enough juice in the battery to turn the lights on in the car but not turn over the engine. My first idea would be to try and boost the car with jumper cables and if it starts I would 100% say the alternator if not then void my theory lol.What about it?