That “Check Hybrid System – Turn Off Engine” warning on your 2017 Hyundai Sonata Hybrid usually means there’s a fault in either the high-voltage battery system, inverter, hybrid control unit, or electric motor. When the car limits your speed and throws that message, it’s entering limp mode to protect itself.
Since you're able to clear the code with a scanner and drive normally (until highway speeds), it likely means one of the hybrid system components is failing under load (like when extra power is needed at higher speeds).
Here’s what you can do:
-
Pull the exact trouble code with a scan tool that reads hybrid-specific systems. A generic OBD2 scanner might not be enough. You need something that can read hybrid battery management or inverter faults (like P0A94, P1A10, etc.).
-
Check the inverter coolant system. Overheating in the inverter can trigger this issue. Make sure the coolant level is good and the inverter pump is running.
-
Inspect the high-voltage battery state of charge. If it’s degrading, the system will cut performance under high load.
-
Check for recalls or software updates. Hyundai has issued hybrid system updates in the past.
And yes, this OEM repair manual does cover full diagnostics for the hybrid system, including troubleshooting flowcharts, sensor specs, and step-by-step repair procedures. If you want to go deeper and do your own diagnostics, it’s the best tool to have on hand.
Let me know the code you pulled, and perhaps we can help you further.
