Had this occur last week on our 2015 Hybrid Accord. Just got the car in mid-May and haven't had any services/repairs needed yet. In my case, having already seen this thread I just pulled off onto the shoulder and shut-off/restarted the car. It was probably less than 60 seconds from error indicator until I shut off the engine. I did notice the engine was running, and running at mid-high range RPM when I stopped on the shoulder. I guess it was trying to recharge the battery but it wasn't the normal idle speed engine recharge such as if you were at a stop light or in a drive through. Upon restart I didn't have a check engine light. Upon restart it was 100% normal.

Hope it logged the error.

I wiill be taking it in for an oil change this weekend and will ask them to pull codes and make sure all software is up to date.

 

UPDATE: thought my problem was fixed with the software update 2 weeks ago, but the same error message appeared again for the last 2 days in a row. Took the car back to the dealership today, this is the 4th time in a little over a month. They gave me a loaner this time while they're trying to replicate the problem.

Also, I saw that Honda finally issued a recall regarding this problem.

Edmunds.com article:
WASHINGTON — American Honda Motor Co. is recalling 6,786 2014-'15 Honda Accord Hybrid sedans because of a stalling risk, according to the National Highway Traffic Safety Administration.

"Electrical interference may cause the hybrid system to switch into fail-safe mode, disabling the gasoline engine, limiting the vehicle's speed to 40 mph and functioning only on battery power," NHTSA said in its recall summary. "Once the battery is discharged, the vehicle will stall.

"A vehicle stall increases the risk of a crash."

No injuries have been linked to the recall, said Honda in a statement. The problem was discovered through the warranty-claim process.

The affected Accord Hybrids were built from August 29, 2013 to May 30, 2015.

Honda dealers will update the hybrid system's software. The recall is expected to begin on November 6. Owners can contact Honda customer service at 1-888-234-2138.

Edmunds says: This recall will get started in a month, but your Honda dealer is available if you have any immediate questions or concerns.

 

from autoblog.com article:

RECALL Subject : Hybrid System may go into Fail Safe Mode

Report Receipt Date: SEP 25, 2015
NHTSA Campaign Number: 15V602000
Component(s): HYBRID PROPULSION SYSTEM
Potential Number of Units Affected: 6,786
All Products Associated with this Recall
Vehicle Make Model Model Year(s)
HONDA ACCORD HYBRID 2014-2015

Details

Manufacturer: Honda (American Honda Motor Co.)

SUMMARY:
Honda (American Honda Motor Co.) is recalling certain model year 2014-2015 Honda Accord Hybrid vehicles manufactured August 29, 2013, to May 30, 2015. Electrical interference may cause the hybrid system to switch into fail-safe mode, disabling the gasoline engine, limiting the vehicle's speed to 40 miles per hour and functioning only on battery power. Once the battery is discharged, the vehicle will stall.

CONSEQUENCE:
A vehicle stall increases the risk of a crash.

REMEDY:
Honda will notify owners, and dealers will update the hybrid system software, free of charge. The recall is expected to begin November 6, 2015. Owners may contact Honda customer service at 1-888-234-2138. Honda's number for this recall is JT7.

NOTES:
Owners may also contact the National Highway Traffic Safety Administration Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153), or go to www.safercar.gov.


Statement by American Honda Regarding Cell Voltage Sensor Recall: 2014-2015 Accord Hybrid

Oct 5, 2015 - TORRANCE, Calif.

Honda will voluntarily recall 6,786 model-year 2014-2015 Accord Hybrid vehicles in the United States to update the hybrid system software related to the hybrid battery cell voltage sensor (CVS), free of charge. No injuries have been reported related to this issue, which was discovered through the warranty claim process.

The CVS may not have sufficient electrical noise toughness, which may result in the CVS incorrectly interpreting electrical noise from the hybrid battery inverter and motor circuits. If the CVS incorrectly interprets the electrical noise, it can cause the vehicle to switch to a fail-safe electric vehicle (EV) mode in which the vehicle uses the electric motor for propulsion, with braking and steering functionality operating on electric power only. If the vehicle switches to fail-safe EV mode while cruising at highway speed, the internal combustion engine will shut off with visual and audible warnings and the vehicle will experience a sudden loss of power, with the maximum speed limited to approximately 40 mph. Once in fail-safe EV mode, the vehicle may be able to travel for up to two miles at which time the hybrid battery will likely completely discharge. If the battery completely discharges while the vehicle is still in operation, the vehicle will stall, increasing the risk of a crash. The software update will prevent misinterpretation of the noted electrical noise.

Honda is announcing this recall to encourage each owner of an affected vehicle to take it to an authorized dealer as soon as they receive notification of this recall from Honda. Mailed notification to customers will begin in early November, 2015. Additionally, owners of these vehicles can determine if their vehicles require repair now by going to www.recalls.honda.com or by calling (888) 234-2138.

 

Hello everyone!
I have a 2014 Honda Accord Hybrid Plug-in with 69k miles.
Yesterday I was driving to Santa Cruz with my daughter and the "Power System Problem" & check engine lights came on. I saw this thread and was scared as hell to drive over highway 17 to make it to the dealership in San Carlos, especially with my 6 year old in the car. I bought the car used with 40k on it. I have the certified Honda Warranty which is up to 100k miles & I bought the extended warranty for $2500 when I bought the car back in Nov 2017. The dealer called me today and told me there was "2 problems" with it and that my warranty only covers one of them, the cheap one. The other is $2000 just for the part and that he was going to talk to his supervisor to see if they could get me a discount. He said the recall doesn't apply to this problem. I am ****** Fried!!!!!! Never ever should a car with that low of miles need $2000 worth of work, Especially with 2 warranties! He said my $2500 warranty expired Nov 2018. I can barely afford the $380 per month I am paying for the car now. Anyone have any suggestions? I am not paying $2000 just for parts and god knows how much for labor in a car that I already pay up the ying yang for. I would never have bought this car if I knew it was gonna do this. I will not be a happy customer and will not hesitate to call 7 on your side if they try to make me pay that ridiculous amount to fix a problem that Honda should be responsible for in the first place. Thanks everyone!

 

Since my last and final visit back in 2015, I have not had this issue again, I'm nearing 50k on my 2015 Accord Hybrid. The dealer I went to replaced the PCB? From what I understand, its similar to the motherboard on a PC. The cost was over $6k but the warranty covered it.

If you're able to, try to take it to a different dealer and see if they will honor the extended warranty you paid for. Your last recourse is threatening them with bad press as you sugguested. I would throw in negative reviews on google, yelp, dealerrating, edmunds, etc.