Traction control light on and car won't start

I have a 2011 Elantra and lately when I've gone to start the car its completely dead. Once I finally get it started, the traction control light comes on and the tachometer drops to zero. I replaced the battery a couple of weeks ago, which seemed to fix the problem, but now its happening again. Any ideas what could be the problem?

 

First off: HYUNDAI, IF YOU'RE LISTENING, YOU NEED TO FIX THIS!!! Hyundai should be paying for these repairs regardless of warranty status, as this is seems to be a common issue.

I had the exact same issues with my 2018 Hyundai Elantra. Tachometer dropped to zero. Very little acceleration. Traction control light comes on. Turning engine off and back on again fixed it at first, but after a while, it was a 50/50 chance. Then it started doing it while I was driving. (Also had my battery replaced and thought that fixed it at first!)

SOLUTION: Replaced the crankshaft position sensor and the camshaft censor. Completely fixed it.

A couple things here that hopefully help further:
1. The proper diagnostic codes won't show up if your instrument panel isn't showing the check engine light. Keep this in mind if a mechanic says they are not seeing any codes relating to these sensors. (This happened to one of the mechanics I took it to the first time they tried.)
2. I've heard over and over again that mechanics can't properly diagnose this (either for the reason stated above or because they just can't replicate the issue at all), so don't hesitate to tell them to just go ahead and replace the sensor(s) even if they're not seeing the relevant code.
3. You may want to just start with the crankshaft position sensor rather than doing both at once. This is the main one I've seen others on these forums mention. I only had both replaced since we were seeing both codes.

Hope this helps!!