Both Side Mirrors Not Working? Step-by-Step Automotive Troubleshooting on a 2016 Hyundai Sonata
If you’ve ever gotten into your car and realized neither side mirror will adjust, you know how frustrating—and potentially unsafe—that can be. This is one of those issues that seems simple on the surface but can quickly turn into a guessing game if you don’t approach it the right way.
In this case, we’re working on a 2016 Hyundai Sonata with a complaint that both exterior mirrors were completely inoperative in all directions. No movement, no sound—nothing.
When you’re diagnosing car problems like this, especially when both sides fail at the same time, it’s critical to slow down and think logically. Jumping straight to parts replacement without testing is how people waste time and money.
Let’s walk through this one step-by-step so you can see how proper automotive troubleshooting leads to a confident, accurate repair.
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Vehicle Overview
We’re working with a 2016 Hyundai Sonata, a mid-size sedan equipped with electronically controlled power mirrors integrated through the driver door module and switch assembly.
Vehicle Concern
The issue was straightforward:
Both side mirrors would not adjust in any direction. No noise, no movement—completely dead.
This type of symptom immediately raises a few key questions during automotive troubleshooting:
Is this a shared power issue?
Is the switch or module failing?
Or do we actually have component failure on both sides?
Initial Inspection
The first step in diagnosing car problems like this is always to check the basics.
Since both mirrors were affected, the suspicion leaned toward a shared circuit—most commonly a fuse or module issue.
Using the wiring diagram, several relevant fuses were identified:
Memory fuse (7.5A)
Module fuse (10A)
Memory 1 fuse (10A, depending on trim level)
Instead of guessing which one applied, every fuse in the interior fuse panel was checked.
Result?
All fuses tested good.
That’s an important turning point in the diagnostic process. At this stage, many less experienced technicians might still replace a fuse “just in case” or move on to guessing. But proper automotive troubleshooting means verifying the circuit, not assuming.
Codes (if applicable)
No fault codes were present related to the mirror system.
That’s not unusual. Many mirror systems are simple motor-driven circuits that don’t always report failures unless there’s a module communication issue.
Diagnostic Process
With power supply ruled out, the next step was to verify whether the mirrors were actually receiving commands.
This is where the Power Probe 3 comes into play.
The left mirror glass was carefully removed to access the motor connector. From there, the circuit was backprobed while operating the mirror switch in all directions.
Here’s what was found:
Power was present for each directional command
Ground was present where expected
Voltage changed appropriately when switching directions
This is a critical moment in diagnosing car problems.
At this point, you’ve effectively proven:
The mirror switch is working
The door module is functioning
The wiring from the switch to the mirror is intact
In other words, the entire control side of the circuit is doing exactly what it should.
So what’s left?
The component itself.
Key Findings
The mirror motors were receiving proper power and ground signals for all directional inputs, but there was no response—no movement or sound.
That tells you the motors are not converting electrical input into mechanical movement.
This is classic internal motor failure.
Even though it may seem unlikely at first, it is absolutely possible for both mirror motors to fail, especially on vehicles exposed to:
Moisture intrusion
Temperature extremes
Long-term wear
Internal gear binding
Final Diagnosis
Both exterior mirror motors have failed internally and require replacement.
At this point, there’s no need for further circuit testing. The system has been fully verified, and the failure has been isolated to the components themselves.
Common Causes
When dealing with symptoms like this, there are a few common causes technicians consider early on:
A blown fuse is often the first suspect, especially when both mirrors stop working at the same time. In this case, all fuses were good.
A faulty mirror switch is another common issue, but that would not allow proper voltage output to the mirrors like we saw here.
Broken wiring, particularly in the door jamb, is also very common. However, consistent and correct voltage at the mirror connector rules that out.
That leaves internal motor failure—which is exactly what this turned out to be.
Lessons for Buyers / DIYers
This is a perfect example of why proper automotive troubleshooting matters.
If you’re not testing the circuit and just replacing parts based on symptoms, you could easily:
Replace the switch unnecessarily
Tear apart wiring harnesses chasing a problem that isn’t there
Waste hours (or days) guessing
For anyone getting into diagnosing car problems, here are a few key takeaways:
Always verify power and ground at the component before condemning it. That one step alone eliminates a huge amount of guesswork.
Don’t assume a shared failure always means a shared cause. Sometimes, two components really do fail independently.
Use wiring diagrams. Modern vehicles are too complex to diagnose blindly.
And if you’re shopping for a vehicle, this is exactly the kind of issue that might not be obvious during a quick test drive but can cost you later.
Don’t Get Burned on Your Next Used Car
If you’re thinking about buying a used car—or even if you already have one—this is exactly the kind of problem that can slip through the cracks and cost you big money later.
After 35+ years in the automotive field, I’ve seen firsthand how often people end up with vehicles that have hidden issues just like this.
That’s why I put together a simple Used Car Guide to help you understand what to look for and how to avoid making a costly mistake.
It’s a quick, practical guide designed to give you the right mindset and approach before you buy.
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Disclaimer
Disclaimer: Some links in this post may be affiliate links. I may earn a small commission at no extra cost to you. I only recommend tools I personally use and trust in real-world diagnostics.
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