Nissan Sentra Check Engine Light Causes & DIY Diagnostic Tips

The check engine light (malfunction indicator lamp (MIL)) is a small but important light on your Nissan Sentra’s dashboard. It can indicate a variety of issues with your Nissan engine, some more serious than others.

In this blog post, we’ll review the most common causes of a check engine light Nissan Sentra. Furthermore, we’ll provide diagnostic tips for DIY owners who want to figure out the problem on their own without the help of a shop.

Nissan Sentra Check Engine Light Causes & DIY Diagnostic Tips

Is the Check Engine Light Flashing?

The check engine light on the instrument panel will flash when the Engine Control Module (ECM) enters fail-safe mode. Or light up your Nissan identifies the same problem on two back-to-back trips. If the check engine light is flashing, the problem will likely be urgent, so stop driving immediately to prevent severe damage. Get your Nissan towed home or to a garage. If the light is on but not flashing, you have a little more time. But you still need to find out why to see if you need to take action.

The first step is to check for any problems that are easy to see. Check if anything is loose or disconnected. We’ve listed a few likely candidates below. If you don’t see the problem, you can use your Nissan’s trouble codes for more info. We’ll walk you through how to do that too. So read on.

Loose or Defective Gas Cap

A loose or defective gas cap is one of the most common reasons for a check engine light to come on. The gas cap is responsible for keeping fuel vapor from escaping out of the fuel tank. When it’s not working properly, fuel vapor can escape and trigger the 2015 Nissan Sentra check engine light. If you’re unsure whether or not your gas cap is loose or defective, you can remove it and inspect it for damage. If it looks damaged, replace it with a new one. If it’s just loose, tighten it until it clicks three times. 

Faulty Oxygen Sensor

A common reason for the 2015 Nissan Sentra check engine light coming on is a faulty oxygen sensor. The oxygen sensor gathers data about the amount of oxygen in exhaust gases and sends it to your Nissan’s computer to adjust the air/fuel mixture. With the right mix ratio, the car runs smoothly and has no problems. A faulty oxygen sensor sends the wrong information, so the air/fuel mixture gets out of wack, triggering the check engine light. 

Catalytic Converter Problems

The catalytic converter is part of the emission control system, and its job is to convert harmful emissions into less harmful ones. If there’s a problem with the catalytic converter, it can cause an increase in emissions, which will trigger the check engine light.

Mass Airflow Sensor Problems

The mass airflow sensor is responsible for measuring the amount of airflow entering the engine so that the computer can adjust the air/fuel mixture accordingly. If there’s a problem with the mass airflow sensor, it can cause the mixture to be too rich or too lean, which can trigger the check engine light on a Nissan Sentra.

Check Engine Light Codes Nissan Sentra

You don’t need to go to a Nissan dealer or car part shop to read your Nissan’s engine codes. You’ll need to the car into diagnostic mode, then check the engine code against Nissan’s list online or in your owner’s manual. Here’s how:

How to Set Nissan Sentra’s ECM in Diagnostic Test Mode II

  1. With the accelerator pedal pushed down all the way, turn on the ignition switch and wait 3 seconds.
  2. Please repeat the following steps five times in total within 5 seconds.
  3. Push the accelerator pedal all the way down.
  4. Remove your foot from the accelerator pedal completely.
  5. Wait 7 seconds, fully depress the accelerator pedal and hold it for approximately 10 seconds until the check engine light flashes.
  6. Remove your foot from the accelerator pedal completely.

You are now in Diagnostic Test Mode II.

How to Read Nissan Sentra’s Trouble Codes Diagnostic Test Mode II

Each flash indicates a digit in the engine code. For example, ‘3’ would be shown as 3 flashes. There will be a short delay (1.3 seconds) before the ECM starts to flash the next digit. Don’t worry if you miss it the first time; the pattern will repeat so you’ll have several chances. When you get the code, look it up in Nissan’s list online or in your owner’s manual.

2015 Nissan Sentra Check Engine Light Reset

Before you reset your Nissan Sentra’s check engine light, make sure you’ve completed your diagnosis. Once you reset, the memory clears.

The simplest 2015 Nissan Sentra check engine light reset method is disconnecting your Nissan’s battery for more than 24 hours. This clears the memory.

The other option is to set the ECM in Diagnostic Test Mode II, then press the accelerator pedal to the floor for at least 10 seconds.


If your check engine light Nissan Sentra comes on, don’t panic! It could be something as simple as a loose or defective gas cap. There’s a good chance that you can diagnose the problem and it fix yourself.  

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news