Thank you for your responses. The respones are helpful; I'm surprised Honda has not responded to this because it seems like a life safety issue. Imagine trying to figure out why your car is slowing down on the freeway from 65 miles an hour while you press the gas, and traffic around you is still doing 65.
This seemed to be more common very early in Clarity production, reports like this are very rare now. What year is your Clarity, also what is the manufacture date (located on driver door jamb). How many miles on it, how long have you owned it?
Also not questioning what you experienced, but the more common issue reported (again mostly from a couple of years ago) is a very loud engine, some have described it as the engine is redlining. Based on these reports there may be some type of glitch that makes the RPM shoot up very high to an alarming level (although not harmful to the car), but most of that power is going to the battery not to the wheels, thus the sensation that the car has slipped out of gear (metaphorically as Clarity does not have gears, it doesn't even have a CVT). There is a theory that when this happens some people assume based on the sound that they are pressing the accelerator to near maximum so they don't press it any further, thus believing the car will not accelerate, when actually it would if they would have pressed the pedal farther.
Realistically it's difficult to gauge how far you are pressing the pedal, other than when the pedal is to the floor, most of us gauge accelerator pedal position by engine sounds or acceleration. So the theory again is that when people experience super excessive high RPMs, the pedal is only slightly pressed, enough to only barely maintain speed, but the high engine revs causes the driver to think they are pressing the pedal more than they really are, thus creating a sensation that the car will not accelerate.
Again not saying this was your situation, but do you remember if you tried pressing the pedal all the way to the floor? Any chance you glanced at the power gauge during this time? I understand if you didn't as an incident like this can be quite distracting, but it would be helpful if it happens again to watch the power gauge to see what it indicates during the high rev situation. In preparation you may want to watch the power gauge in normal driving perhaps more than you normally do and memorize what levels the power gauge indicates at different accelerations. Then if the incident happens again you will have something to compare it to.
As for an RPM gauge, there are relatively inexpensive OBD2 bluetooth devices that you use with a phone app. Torque Pro is a popular app, the free version will show RPM. Again it would be good to use it in regular driving and note typical RPM's, then if the incident happens again you will have something to compare to. This won't necessarily help solve it but it will give you more of a qualitative description to report to the dealer.
, Purchased the 2019 Honda Clarity in March of 2020 brand new. When it happened on 8/26, I noticed the sound first, then looked at the speedometer and saw the loss of speed from 39 miles per hour and continued to drop. I pushed the pedal a few times, and speed continue to drop. The second time was from a dead stop, I was able to get up to 19 miles an hour, and the car would not go past that. In both cases, what seemed to resolve the inability to accelerate was turn off HV mode for a moment (less than a minute), and re-enabling it again.
I'm waiting on the BlueDriving OBD-II; hopefully I can log other data should the event happen again.
, thank you for the link; it helps to understand this a lot better.
with our 2018 Clarity Touring a number of times the first year we owned it. Sometimes it would happen in the winter during severe cold, other times in the mountains with a fully loaded car. Very disturbing and also terribly dangerous, so I filed a formal complaint with the National Traffic Safety Board. In reference to an earlier post, pushing the accelerator pedal to the floor does no good in those situations. I took it to our local Honda dealer and they exerted a good faith effort by hooking up a computer and driving with me but we couldn't duplicate the problem -- no surprise there. I considered using our state's Lemon Law due to safety concerns, but we haven't had any problems the last 1.5 years so decided to keep it. Am heading to the mountains again in a couple weeks so will be interested to see if we encounter the same problems again. I know of no solution, other than keeping your battery as fully charged as possible whenever in HV mode.
, It seems like the problem I'm having now. It happens when it happens, and it happened again yesterday, I took the car into the shop today, and Honda could not find anything in the codes.
Thanks for the detailed info. I read all of the NHTSA reports a while back and I found eighteen that described a similar complaint, car would not accelerate, slowed down to 20 mph, etc. But most of them were from a couple of years ago there were very few recent reports. When I read the reports it sounded like what you experienced, in my opinion they couldn't all be explained by the high RPM theory where drivers are misled by alarmingly high RPM's into believing the car would not accelerate. Unfortunately none of the reports that I read specifically stated that they tried pressing the pedal to the floor, so there was no way to prove this wasn't the case to those who were dismissing the reports as just new owners who didn't understand how the car works. Although perhaps coincidentally I did notice that most of the reports were from people who had only owned the car for a relatively short time. It makes me wonder if perhaps the problem was a software glitch that somehow clears up as the car is driven longer and builds up more data. Or maybe the problem was fixed in a software patch that the owner may not have been aware occurred. Just guesses as a way to explain why the problem seems to have mostly gone away.
, I am wondering the same thing; it seems like if this were a hardware problem there would be "codes" (smoke, sounds, etc.) but for Software I would expect an exception code for scenarios that did not meet the various use cases, unless it is an "undocumented feature" that perhaps Honda may not be aware.
Here are the details fo the occurrence on 2020/09/07 approx 3 PM.
(1) State of the car:
The car was in HV mode with 45% of battery
Pressed the gas and the engine revved and did not get past 12 miles per hour.
Driving Southbound on the 15 freeway downhill in Stop and Go traffic. I noticed the pressing the accelerator the would engine rev, and the car seemed to have trouble accelerating; this time, I unable to drive past 12 miles an hour.
Note: The 12 miles per hour is strange because I would not expect this to occur, considering the driving direction is downhill.
(4) Workarounds/What next?
What seemed to resolve the inability to accelerate was to disable HV mode, drive using electric for a bit, then turn HV Mode back on.
Took the car into the shop today, and Honda reported that there were no error codes that would indicate there was a problem and that Honda was unable to replicate the issue.
I've got a Blue OBD arriving, so I can start logging other engine parameters when this occurs. I'll share what I find the next time this happens.