Side lights on a car NISSAN Sentra VII (B17) (08.2012 - ...)

It is difficult to answer unequivocally. A non-working part shows that there is a problem in the circuit and indicates the circuit. But the problem is that there are many connections and devices in the circuit.
It is necessary to check the entire circuit and possibly replace parts in the circuit one by one - the method of exclusion.
But sometimes everything is trivially simple, the problem is in some connection, diagnostics are needed. Perhaps it is a lamp socket or a wire connection.

The intermittent flickering and failure of your 2014 Nissan Sentra’s side lights, despite bulbs and fuses checking out fine, is most commonly linked to alternator or electrical system issues rather than the bulbs themselves.

Here’s a breakdown of likely causes and next steps:

Alternator Problems:
Flickering lights often indicate the alternator is struggling to maintain a steady voltage output. A defective alternator or a faulty diode inside it can cause voltage drops and spikes, leading to flickering or dimming of exterior lights, including side lights. A video example with a similar Nissan Sentra showed that disconnecting the alternator stopped the flickering, confirming the alternator as the culprit.
Signs of alternator issues include flickering lights, dimming or overly bright lights, battery warning light on the dash, and electrical accessories malfunctioning.

Electrical Connections:
Loose or corroded wiring connections, especially at the alternator or fuse box, can cause intermittent power delivery and flickering. One owner resolved flickering by tightening the electrical connection on top of the alternator.
It’s worth inspecting and cleaning the alternator terminals, battery terminals, and related wiring harnesses.

Voltage Regulator:
Often integrated into the alternator, a faulty voltage regulator can cause unstable voltage output, leading to flickering lights.

Other Causes to Rule Out:
While you’ve checked bulbs and fuses, ensure the light switch itself isn’t faulty, as a failing switch can cause intermittent lighting issues.
Also, check for any aftermarket electrical modifications that might be causing wiring issues.

What to do next:
- Have your alternator and battery tested at a reputable garage or auto parts store to check voltage output and charging system health.
- Inspect and clean all relevant electrical connections, especially at the alternator and battery.
- If the alternator is faulty, replacement is usually the best solution.
- If the problem persists after alternator replacement, have the lighting circuit and switch inspected by a professional.

In summary, your symptoms strongly point to a faulty alternator or poor electrical connections rather than bulbs or fuses. Addressing the alternator and its wiring will likely resolve the flickering side lights on your 2014 Nissan Sentra.