In my 2016 Miata, the electric power assist for the steering has died but the fuse for it is fine. It was working fine when it was towed to a dealership to have the manual transmission rebuilt and it was dead when I picked it up. Any ideas?
Sajeev answers:
First, let’s mention that ND Miata transmission replacements are a thing. Wow.
Gearbox removal is no cakewalk, but this long video suggests there’s no need to muck with the electric power steering system. So either the dealership addresses the issue or maybe, possibly, the system woke itself up after a few driving cycles?
Once again, no matter the existence of a valid diagnostic tree for electric power steering systems, the joy of owning a car under warranty means this isn’t your problem!
One thing I’ve learned in my years working in auto retail is mistakes are nearly impossible to avoid: too many moving parts (so to speak) are in play, which is the nature of this business. So mistakes shall happen, but will they resolve the problem to your satisfaction?
[Image: Mazda]
Send your queries to sajeev@thetruthaboutcars.

It is clear we’re dealing with malevolent possession.
Inari will need to be appeased.
Taxidermy fox to the temple is the traditional offering, but a sushi roll thrown in the fox enclosure at your local zoo will work. Fried tofu is preferred by the Kitsune.
This will be the best way.
Tranny Tribulations? That could lead to a TERF war.
lol
I’d check the electrical connections to the EPS – maybe a connector is off or loose, or maybe they managed to break something (like a wire) when they were working on it.
I’ll wager that there are custom OBD-II codes (PIDs) for their EPS system, that could be read by something like a Snap-on code scanner (but not by the $50 ones they use at AutoZone to tell you that you need to buy one of their cheap Chinese-made ValuCraft parts).
When I had my F150 (featured in a Piston Slap about gear whine) and had the flatbed installed I picked it up, both the AC and the back up lights were not working.
Body shop couldn’t figure out why.
After a short and sweaty drive to the gas station I opened the fuse box and found one that had wiggled loose but was still held in place (didn’t fall out) some checking of fuse tightness solved both problems.
Just out of curiosity, how did you figure out that your reversing lights were not operable? Did someone alert you to the fact, or did the truck itself produce an error?
The shop (I worked with the owner’s wife for several years in a previous teaching assignment) called me up to pick it up and admitted that they couldn’t figure out what was causing the issue. Since it was sitting inside the shop and the windows were down, they didn’t know about the AC issue.
Good guys but it was their first time doing that job and it was trial and error. Fortunately they worked cheap.
Oh, okay! That makes sense!
I’ve learned the hard way that fuses can look good but are bad. I would change the fuse and get a fuse tester as a my first step.
First, just take it back. They’ll fix it for you.
I suspect they left a ground strap loose when doing the transmission. Those racks use a decent amount of current, and a loose or missing ground strap can keep them from working properly.
This.
Random guess: a sensor on or near the steering rack was disconnected and not plugged back in.
Surprised that the OP could even turn the wheel, as from what I understand, when an EPS system is on the fritz, it’s damn near impossible to turn the wheel, versus when a hydraulic system goes Tango-Uniform! I probably would have sensed that something was amiss before I left the parking lot of the shop.
Of course, this is a Miata, so there may not be a need for much, if any, assist.