Can't say with certainty, but with your symptoms it sounds like it has something to do with the ABS system. The brake pedal pulsating that you're getting is from the ABS module thinking you're engaging in a emergency stop; brake pedal completely smashed, and the pulsation is the system releasing some brake application to prevent the brakes from locking up. Now yes, you're not doing that but something along that system is not communicating properly and causing you to go into an ABS/full emergency stop event when that is not what you are doing.

 

First of all, make sure to keep it charged while awaiting repair:

How to Completely KILL a 500e (4 easy methods)

10/10/22 addition: Maybe easiest yet: Just don't get U69 done! That's all! :oops: (To learn about U69, click here). Then when the 12V starter battery dies with no warning, the HV pack will kill itself trying to recharge it. 4/17/22 addition: To completely kill a 500e permanently dead, just...

www.fiat500owners.com

Then make sure your humidity sensor is left disconnected:

Humidity Sensor SUCKS! (until you unplug it)

It activates the range-reducing A/C compressor, without even lighting the A/C button! It deactivates recirculate, which can also reduce range by heating/cooling outside air instead of pre-conditioned cabin air. It can cause false alarms including ABS, RBS, HSA, ESC, PRND, SRS (airbag), etc...

www.fiat500owners.com

Then try these other tricks to clear errors:

Clearing Warning Messages/Error Codes (updated)

Last edit 9/28/22. List of edits & credits at the bottom. Sorry if I missed anyone (PM me if I did). The 500e sometimes shows a warning or error even when everything is working fine, & sometimes something won't work JUST due to an erroneous code. There are really only 6 things to try. Here's...

www.fiat500owners.com

 

The pulsating isn't what your thinking. It's the regen coming on and off every other second rapidly as by the KW regen reading on the dash confirms, when the regen cuts off the car goes into a coast no matter how hard I push the pedal. The car has no idea that the pedal is being pushed (which i can't believe all the electronics can even let happen). I'm starting to wonder if i'm maybe having some grounding issues.

 

Ya, a TurboPanda would never have this issue, but I understood it from your description of "dash regen says 45kw, 7kw, 39kw, 7 kw, 36kw, 7kw, 29kw ", so my own easy DIY suggestions above still apply. Please try them & let us know how it goes.

Also, everyone else reading this, if it ever happens to you, & you're going to crash from brake failure, use the handbrake. It's one advantage of having a classic mechanical system.

 

I took it to Perkins in Colorado Springs as I saw on another post that they were (at least at one time) certified to work on the E's. I was going to check the humidity sensor to see if was hooked up but forgot. They are supposed to do diagnostic sometime this week. I'm kinda done on trying to diagnosis the issue myself, but if they can figure it out i'll post it up here for future research purposes.

 

Thanks for the update, & thanks in advance for posting any developments.

I understand your attitude somewhat, since I've rebuilt gas engines myself, as well as carburetors, fuel pumps, etc, & this thing is more like a computer that happens to be on 4 wheels.

But don't be surprised if a dealership can't figure it out, or gets it wrong, since their techs were VERY insufficiently trained, especially considering that much of the knowledge has only been learned quite recently, & only then just by users' own trial & error.

As a "4-wheeled computer", often the best way to fix it is to reboot after deleting unnecessary stuff. In this car, the humidity sensor needs deleting, & the reboot can require up to 30 hours with the 12V disconnected, & sometimes as many as 4 different disconnect/reconnect sequences for the HV plug under the back seat.

To me it's not all that much work compared to replacing a clutch.

 

It's more of my knowledge in electric cars and what they look at to make certain things do certain things is very limited. Even being in my late 20's i still have to have my girlfriend constantly help me with my phone and computer from time to time. It was also my daily driver and driving my v10 3/4 ton truck to work takes nearly $150 a week in fuel so i'm just ready to either have it fixed or to get it traded off. I'm not fond of dealers since they are expensive and most "techs" are fresh out of school or off the street but they told me they had a dedicated EV tech when i called to make ceratin they had someone who actually knows how to work on them so fingers crossed on that.

 

Ya, I hope it works out for you.

Just keep in mind that you may already know something that the dealer tech doesn't. For example you know to leave the humidity sensor permanently unplugged, which they likely don't (click here).EDIT: That thread was deleted by the author. It showed pretty bad dealership incompetence. Coincidence?

Your girlfriend will likely agree that it very often works to delete extras & then reboot, for any computer, such as a phone, DVR, Keurig, or 500e, especially if it's 7 years old like yours (no offense, mine is even older).

My DVR is newer than my 500e, but it needs reboot more often. My friend's Keurig is even newer than my DVR, but it needs reboot even more often!

 

Well here's where the car stands, humidity sensor was already disabled apparently, car has been factory reset twice. The certified tech for the E doesn't know whats wrong but wants to replace all ABS sensors with expensive Fiat ones (already replaced) and put a brand new ABS module to see if that fixes the issue of the first problem of the rear ABS sensors cutting in and out. Don't know why the accelerator pedal also cuts in and out. So i feel like i just paid $700 for them to go yep don't know what's wrong so better start throwing money at it. They are supposed to have someone look at it and give me an offer on it. The car isn't as useful as it was when i first bought it and isn't really saving me money at this point so i'll be going back to a ICE car. Thanks for the suggestions though. Probably wait a few years until the serviceability of EVs become more common and get one with more range and fast charging so it's more useful in my area.

 

So, my car just started having a similar issue. It started with a regen pulsating current like yours; but, evolved into only being able to dive under 40mph without the ESC light flashing and the ABS pulsing. I did not know anything about the humidity sensor thing; but, the dealer want over $2600 for the ABS module replacement. $1447.20 for the module, $653.59 in labor, and $253.50 for the AC evac and recharge. Because, they insist the AC line has to be removed to get the ABS module out.

 

So after 6 months of it sitting at the dealer waiting in an ABS module (they thought that was what was wrong with mine) New ones just don't exist and probably never will exist, you'd be stuck with a used one. We had already replaced the rear ABS sensors but after finding out that a new module will never come after having it ordered for all those months we tried replacing both rear ABS sensors again and it fixed it, zero issues now. Apparently both rear ABS sensors failed and the first replacements (unknown brand form independent shop) wouldn't communicate with the module correctly for some reason. Mopar replacement rear ABS sensors, new 12v battery and diagnosis for $515. Car is back to perfect.

 

Well, thanks for the update. Yeah, I've been told that the new one (p/n 6822668AC) is on manufacturer hold due to supply chain issues. But there are 2 of the predecessor models left (68226688AB)

Did your car have any errors stored that related to the ABS sensors? Also, by ABS sensors, you mean the wheel speed sensors right?

 

Don't know about stored codes i'd have to find the dealer print out but i don't recall them saying anything about a sensor specific code. They suggested a new 12v, ABS module update, speed sensors, hubs, ABS module in that order. Had service RBS, ABS warnings on, hill hold and traction disabled, speedo was all over randomly working and not working and car would randomly go in and out of limp mode. Also yeah the rear speed sensors.