I'm having the EXACT SAME ISSUE.
2016 Hyundai Sonata Hybrid, Steve Shomo, VIN KMHE34L16GA015823
Since early September 2017, I’ve experienced an intermittent “Check Hybrid System” warning when trying to start the car on long trips. This problem is becoming more and more common when driving continuously at highway speeds. When starting the car, the computer performs a system check and finds this error. At this point, the computer “will not” start the car. The hybrid system refuses to “boot up.”
NOTE: I have never yet had this issue while driving around town locally or for short periods of time. (1 hour or less)
This always happens after driving the car at interstate speeds for 1 or more continuous hours. When you stop to get gas or go into a rest area, the system refuses to “boot up” for 15 to 45 minutes. When the system has had enough time to COOL DOWN?, the car will start and the “red check engine” light remains on.
The first instance was September 6, 2017 returning from Columbus Ohio. I pulled into a gas station to fuel. After filling up, I could not start the car. I’ve attached a video of the dashboard control screen when this happens. (2018-03-09_HEV start up system failure.mov) After repeated attempts, it finally starts after 10-20 minutes and the car electronics “boots up.” Once the diagnostic system allows the car to start, the red check engine light remains lit.
When I returned to Greensboro, I immediately took the car to Capital Hyundai here in Greensboro. A service DTC scan indicated a saved code of P1990. According to the service reports, the code represents a high voltage warning on the electric input line to the Oil Pump. Once the system cools down, or is not being run continuously on the interstate, a test of the electric line to the oil pump comes back with no problems.
On a trip to Boston in October, I experienced the same problem at a service area where I stopped to get gas. The following day after I’d arrived at my destination, I took the car to the Hyundai Village Dealership in Danvers, MA. The DTC scan showed the same P1990 code. They also performed an “engine off” oil pump test which passed.
In late December, after visiting our children and grandchildren in Boston, the car failed to start at a rest area returning to Greensboro in early January of this year. We went inside to eat and after 45 min, the car booted up, again with the red engine light.
During my regular oil change and service I relayed this to XXXXX there at Sport Durst. The DTC scan again revealed the P1990 code, but there was no time to test the system which I presumed would have passed.
we just returned from a trip to Alabama. (March 9-12, 2018) Every time we stopped both going down and coming back, the car would not start. Once we got to our destination and drove around town once or twice, the red engine warning light would go off. The car ALWAYS starts when cold. After returning home on Monday, the red engine warning light just went off this afternoon. (3/13/18)
Here is my uneducated guess. During long periods of driving, there must be some HEAT related to that high voltage line going to the oil pump. This issue stops the computer system check from starting the Hybrid system. When you stop and the electrical system cools down, the car will start normally. Driving around town or locally does not get the system hot enough to create the code.
