Intermittent Power Seat Movement? Here’s How to Diagnose a Failing Seat Motor the Right Way
If you’ve ever dealt with a power seat that works when it wants to, you already know how frustrating it can be. One minute it moves just fine, the next minute—nothing. Then suddenly it works again like nothing ever happened.
This kind of intermittent issue is one of the most overlooked problems when diagnosing car problems, especially during a used car inspection. It doesn’t always set codes, and it can easily be dismissed as “just a glitch.” But in reality, it’s often a sign of a component on its way out.
In this case, we’re working on a 2015 Chevrolet Impala (Chevy SS platform), where the passenger front seat would not consistently move forward and backward. Let’s walk through the automotive troubleshooting process step by step so you can understand how to approach this kind of problem like a pro.
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Autel MaxiSys MS906 Pro TS Scanner
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Power Probe 3 Circuit Tester
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Perfect for quickly verifying power and ground at switches, motors, and connectors without guessing.
Power Probe ECT3000 Short Finder
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Vehicle Overview
The 2015 Chevrolet Impala is a well-equipped full-size sedan, and the Chevy SS trim includes power-adjustable seats with multiple motors controlling forward/backward movement, tilt, and height. These systems rely on a combination of switches, wiring, and electric motors working together seamlessly.
When one part of that system starts to fail, symptoms can become inconsistent and misleading.
Vehicle Concern
The complaint was straightforward: the passenger front seat would intermittently fail to move forward and backward. Sometimes it worked perfectly. Other times, pressing the switch did absolutely nothing.
No grinding noise. No clicking. Just intermittent operation.
This is exactly the kind of symptom that can trick even experienced technicians if they don’t follow a structured diagnostic process.
Initial Inspection
First step in any automotive troubleshooting job is verifying the concern. You don’t assume—you confirm.
Sure enough, the seat movement was inconsistent. At times it responded normally, and at other times it was completely unresponsive in the fore/aft direction.
Next, we checked the obvious:
No blown fuses
No visible damage to the seat track
No obstruction under the seat
At this point, it’s time to dig deeper.
Codes (If Applicable)
In this case, there were no diagnostic trouble codes related to the seat system. That’s common with mechanical or motor-related failures.
This is why relying solely on a scan tool can sometimes leave you chasing your tail. Not every problem sets a code.
Diagnostic Process
Now we move into hands-on testing—the part where experience really matters.
The side trim of the seat was removed to access the seat switch connector. This gives you direct access to the circuit without tearing the entire seat apart.
Using a Power Probe, we tested the switch operation.
Here’s what we found:
When operating the seat switch forward and backward, power and ground were present at the connector.
The polarity changed correctly depending on switch direction (which is exactly what you want to see for a reversible DC motor).
That tells us something critical: the switch is working properly, and the circuit is delivering power as designed.
At this stage, you’ve eliminated:
The seat switch
The main power supply
Ground integrity (at least up to the connector)
So now the focus shifts downstream.
Key Findings
The most important takeaway from testing was this:
Power and ground were consistently present at the motor circuit, even when the seat failed to move.
That’s a big clue.
If the motor is receiving proper voltage but isn’t responding, the issue is almost always internal to the motor itself.
Now add in the intermittent nature of the problem, and you start thinking about one specific failure mode.
Final Diagnosis
The likely cause here is a failing seat track motor with a worn or damaged armature.
Inside electric motors, you have brushes making contact with the commutator. Over time, wear can create “dead spots” where electrical contact is lost depending on the motor’s position.
That explains the symptoms perfectly:
Sometimes the motor lands on a good contact point → it works
Other times it stops on a bad segment → no movement at all
This is a textbook intermittent motor failure.
The plan moving forward is to replace the seat track motor. While the seat is removed, it’s also smart to inspect the wiring harness between the switch and motor for any signs of damage or partial breaks.
Even though testing points strongly to the motor, a quick visual inspection ensures nothing gets overlooked.
Common Causes
Intermittent seat movement like this usually comes down to a few key issues:
Worn motor brushes or commutator (most common)
Internal motor failure or dead spots
Wiring damage inside the seat frame
Loose or corroded connectors
Faulty seat switch (less common if power/ground tests good)
In this case, all signs point to the motor itself.
Lessons for Buyers / DIYers
This is where things get real important—especially if you’re buying a used vehicle.
Intermittent issues like this are easy to miss during a quick test drive. The seat might work perfectly when you check it, only to fail later.
Here are a few used car inspection tips you should always follow:
Take your time operating every power function multiple times. Don’t just test it once and move on.
Pay attention to hesitation, slow movement, or inconsistent behavior. Those are early warning signs.
Understand that electrical components often fail intermittently before they fail completely.
And most importantly—don’t ignore “small” issues. A seat motor might not seem like a big deal, but depending on the vehicle, repairs can add up quickly once labor is involved.
When diagnosing car problems, consistency is key. If something doesn’t behave the same way every time, there’s usually a deeper issue hiding underneath.
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.
👉 https://stan.store/BobbyWhiteside
Affiliate 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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