The Mustang Mach-E GT should be able to put its tires through quite a bit of agony thanks to its upwards of 600 lb-ft of torque. That’s especially true if you deactivate traction control and set about spinning ruts into the earth. It turns out, though, that some Mach-Es sort of lose it after such displays of power, as one owner revealed on a forum earlier this month.
The driver — an individual named Corey — posted a thread over at Mach-E Forum explaining what ensued after he turned off traction control on his Mach-E to make it up an ice-covered incline. “All four wheels were spinning,” Corey wrote, but he eventually made it up the hill. At which point, the car’s dashboard started glitching out like a robot asked to define love. The following messages were displayed:
• Hill start assist not available
• 1 Pedal Drive Fault — Press brake pedal to reduce speed
• Service AdvanceTrac
• Check headlamp system — See manual
• Auto hold fault
• Blind spot fault
• Cross traffic system fault
• Reverse brake assist not available — See manual
Corey said the messages kept popping up every couple of minutes and even prevented him from selecting different drive modes. He wasn’t the only one; two more respondents reported such weirdness, though many others said they subjected their Mach-Es to similar abuse without incident.
The owner finally got his car back this past Monday after a week at the dealer. The issue had been fixed, with the service advisor telling Corey that the garage “had to reset all modules in the vehicle” and highlighting an issue with the steering sensor. The invoice does indeed mention a “network interruption” that threw the steering wheel center find off kilter, then cascaded into the aforementioned errors.
But why? Some in the thread theorized the malfunction could’ve been caused by over-revving and/or “back EMF” — shorthand for counter-electromotive force. I am not an electrical engineer, so I can merely supply Wikipedia’s definition that describes back EMF as “the the electromotive force (voltage) that opposes the change in current which induced it.” Here’s a better, more illustrative definition from an ancient-looking website belonging to the Boston University College of Arts & Sciences:
When something like a refrigerator or an air conditioner (anything with a motor) first turns on in your house, the lights often dim momentarily. To understand this, realize that a spinning motor also acts like a generator. A motor has coils turning inside magnetic fields, and a coil turning inside a magnetic field induces an EMF. This EMF, known as the back EMF, acts against the applied voltage that’s causing the motor to spin in the first place, and reduces the current flowing through the coils of the motor.
Could the back EMF generated by all that wheelspin be frying things behind the scenes? I wondered this myself, so I reached out to an expert — Michael Bream, CEO of EV West, a company in California that sells EV parts, charging equipment and even conversion kits.
Michael told me he hasn’t observed such issues caused by back EMF, but that the likely culprit may be something far more typical:
In the aftermarket (and sometimes repurposed OEM) systems that we do we have not had an issue with back EMF. As a software engineer I would suspect that they are seeing unexpected values, (delta speed at wheel) or something similar that could be causing undefined states in the software, that can contribute to cascading errors. Anecdotally, VW gave us an ID4 to do some development work, and being the Jalops that we are, we pulled the traction fuses and went nuts. Afterward, it took almost a full day for the computers to calm down, reset and cancel all the warning lights. Seemed extremely odd, and for at least half the day we thought we broke the ID4. Total speculation, but I would suspect rushed software to be the cause over back EMF, but that is purely a guess.
A botched software update would explain why some owners ran into trouble while many didn’t. It also could mean this issue isn’t exclusively endemic to EVs. I reached out to Ford for insight but haven’t received a response at the time of writing. I’ll update this story with whatever I hear.
So there you have it: melt the tires of an EV running software that isn’t up to the task, and you might just confuse it so hard it thinks it’s dying. At least it’s not permanent.