How to Check Service Engine Light Codes on Infiniti

Discover how to read and interpret service engine light codes on your Infiniti using simple tools and methods. This guide walks you through OBD2 scanners, manual code reading, and next steps for repairs in 2026.

Key Takeaways

• Use an OBD2 scanner for accurate code reading: Modern Infiniti models require a reliable OBD2 scanner to retrieve diagnostic trouble codes (DTCs) quickly and accurately.
• Locate the OBD2 port under the dashboard: The port is typically found beneath the steering column, near the driver’s knees, and is easy to access.
• Understand common Infiniti engine codes: Codes like P0300 (random misfire) or P0420 (catalyst efficiency) are frequent and often tied to spark plugs or oxygen sensors.
• Manual code reading is limited but possible: Some older Infiniti models allow code retrieval via the ignition key, but this method is outdated and less reliable.
• Clear codes only after repairs: Never clear codes before fixing the issue, or you risk missing the root cause of the problem.
• Consult a professional for complex issues: If codes point to transmission, emissions, or electrical systems, seek expert help to avoid further damage.
• Keep a repair log for future reference: Documenting codes and fixes helps track recurring issues and improves long-term vehicle maintenance.

How to Check Service Engine Light Codes on Infiniti

If the service engine light has popped up on your Infiniti’s dashboard, don’t panic—yet. That little orange or yellow light is your car’s way of saying, “Hey, something’s not right.” But instead of rushing to the dealership or guessing what’s wrong, you can take control by learning how to check service engine light codes on your Infiniti. In this comprehensive 2026 guide, we’ll walk you through every step, from locating the diagnostic port to interpreting the codes and deciding your next move.

Whether you drive a sleek Q50, a rugged QX60, or a sporty Q60, the process is largely the same across Infiniti models. With the right tools and a bit of know-how, you can save time, money, and stress. We’ll cover both modern OBD2 scanner methods and older manual techniques, explain common codes, and offer practical troubleshooting tips. By the end, you’ll feel confident diagnosing your Infiniti like a pro.

Why the Service Engine Light Comes On

Before diving into how to check the codes, it helps to understand why the service engine light—also known as the malfunction indicator lamp (MIL)—activates. This light is part of your Infiniti’s onboard diagnostic system, which constantly monitors engine performance, emissions, fuel systems, and more.

The light can illuminate for minor issues, like a loose gas cap, or serious problems, such as a failing catalytic converter. In 2026, Infiniti vehicles are equipped with advanced diagnostics that can detect even subtle irregularities. Common triggers include:

• Faulty oxygen sensors
• Spark plug or ignition coil failures
• Evaporative emissions system leaks
• Mass airflow sensor issues
• Catalytic converter inefficiency
• Fuel system irregularities

Ignoring the light can lead to reduced fuel efficiency, increased emissions, or even engine damage. That’s why checking the codes promptly is so important.

Tools You’ll Need to Check Infiniti Engine Codes

To read service engine light codes on your Infiniti, you’ll need one or more of the following tools. The method you choose depends on your Infiniti’s model year and your comfort level with technology.

1. OBD2 Scanner (Recommended)

The most reliable and user-friendly way to check codes is with an OBD2 (On-Board Diagnostics, Generation 2) scanner. These devices plug into your car’s diagnostic port and communicate directly with the engine control unit (ECU).

In 2026, OBD2 scanners range from basic $20 models to advanced Bluetooth units that sync with smartphone apps. For most Infiniti owners, a mid-range scanner (around $50–$100) offers the best balance of features and affordability. Look for models that support:

• Reading and clearing DTCs
• Live data streaming
• Freeze frame data (shows conditions when the code was set)
• Compatibility with Nissan/Infiniti systems

Popular brands in 2026 include BlueDriver, FIXD, and Autel. Many now include cloud-based diagnostics and repair suggestions.

2. Smartphone with OBD2 App

If you prefer a wireless option, consider a Bluetooth or Wi-Fi OBD2 adapter paired with a diagnostic app. These compact devices plug into the OBD2 port and transmit data to your phone via an app like Torque Pro, OBD Fusion, or Car Scanner.

This method is great for real-time monitoring and logging data over time. Just make sure your adapter is compatible with Infiniti vehicles and supports the latest OBD2 protocols.

3. Manual Code Reading (Older Models Only)

For Infiniti models from the early 2000s or before, you might be able to read codes manually using the ignition key. This method involves turning the key on and off in a specific sequence to make the service engine light flash in patterns that correspond to codes.

However, this technique is outdated, limited in accuracy, and not supported on most post-2010 Infiniti models. We’ll cover it briefly, but we strongly recommend using an OBD2 scanner for better results.

Step-by-Step: How to Read Codes with an OBD2 Scanner

Using an OBD2 scanner is the gold standard for checking service engine light codes on Infiniti vehicles. Here’s how to do it safely and effectively.

Step 1: Locate the OBD2 Port

The OBD2 port is a 16-pin connector usually found under the dashboard on the driver’s side. In most Infiniti models, it’s tucked beneath the steering column, near your knees. You may need to crouch down or use a flashlight to spot it.

The port is typically black or gray and has a trapezoidal shape. It’s often labeled “OBD” or “DLC” (Data Link Connector). If you can’t find it, consult your owner’s manual—Infiniti usually includes a diagram.

Step 2: Turn Off the Engine

Before plugging in the scanner, make sure the engine is off. This prevents electrical surges and ensures a clean connection. However, keep the ignition in the “ON” position (without starting the engine) so the ECU powers up.

In most cases, you’ll turn the key to the second position—where the dashboard lights up but the engine doesn’t crank.

Step 3: Plug in the OBD2 Scanner

Insert the scanner’s connector into the OBD2 port. It should fit snugly and only go in one way—don’t force it. Once connected, the scanner should power on automatically or prompt you to turn it on.

If using a Bluetooth adapter, ensure it’s paired with your phone before proceeding.

Step 4: Follow the Scanner’s Instructions

Most modern OBD2 scanners have a simple menu system. Use the buttons or touchscreen to navigate to “Read Codes” or “Scan for DTCs.” The device will communicate with your Infiniti’s ECU and retrieve any stored trouble codes.

This process usually takes 10–30 seconds. Once complete, the scanner will display one or more codes, such as P0301 or P0420.

Step 5: Record the Codes

Write down or take a photo of the codes. Some scanners allow you to save or export the data. If multiple codes appear, note them all—they may be related.

Also, check if the scanner provides a brief description of each code. For example, P0300 might show as “Random/Multiple Cylinder Misfire Detected.”

Step 6: Interpret the Codes

Now it’s time to understand what the codes mean. OBD2 codes follow a standard format:

• P = Powertrain (engine, transmission)
• B = Body (airbags, windows, etc.)
• C = Chassis (ABS, suspension)
• U = Network/Communication

The first digit indicates if it’s a generic (0) or manufacturer-specific (1) code. The next three digits specify the exact issue.

For example:

• P0300 = Random misfire
• P0420 = Catalyst system efficiency below threshold
• P0171 = System too lean (bank 1)

Use your scanner’s built-in code library, a repair manual, or a trusted online database like OBD-Codes.com to look up each code.

Step 7: Check Live Data (Optional but Helpful)

Many advanced scanners allow you to view live data from your Infiniti’s sensors. This includes engine RPM, coolant temperature, oxygen sensor readings, and fuel trim values.

Comparing these values to normal ranges can help confirm the issue. For instance, if the long-term fuel trim is consistently above +10%, it may indicate a vacuum leak or faulty MAF sensor.

Step 8: Clear the Codes (After Repairs)

Once you’ve identified and fixed the problem, you can clear the codes using the scanner. Select “Clear Codes” or “Erase DTCs” from the menu.

Important: Only clear codes after the repair is complete. If you clear them too soon, the light may come back on, and you’ll lose valuable diagnostic information.

After clearing, start the engine and monitor the dashboard. If the service engine light stays off, the issue is likely resolved. If it returns, there may be an underlying problem or a new code has been set.

Manual Code Reading (For Older Infiniti Models)

If you own an older Infiniti (pre-2010) and don’t have an OBD2 scanner, you might be able to read codes manually. This method uses the service engine light to flash in sequences that represent numbers.

Step 1: Turn the Ignition On and Off

With the engine off, turn the ignition key to the “ON” position (dashboard lights on), then back to “OFF.” Repeat this cycle three times within five seconds, ending in the “ON” position.

Step 2: Watch the Service Engine Light

The light should begin flashing. Long flashes represent the tens digit, and short flashes represent the ones digit. For example, two long flashes and three short flashes mean code 23.

Step 3: Record the Code

Write down the number. The sequence may repeat, or additional codes may appear. Wait for a pause (usually 3–5 seconds) between codes.

Limitations of Manual Reading

This method only works on select older Infiniti models and may not retrieve all codes. It also doesn’t provide detailed descriptions or freeze frame data. For these reasons, we recommend upgrading to an OBD2 scanner if possible.

Common Infiniti Service Engine Light Codes and What They Mean

Here are some of the most frequent codes seen on Infiniti vehicles in 2026, along with likely causes and solutions.

P0300 – Random/Multiple Cylinder Misfire

This code indicates that the engine is misfiring across multiple cylinders. Common causes include:

• Worn spark plugs
• Faulty ignition coils
• Dirty fuel injectors
• Low fuel pressure

Start by inspecting and replacing spark plugs and coils. Use a fuel system cleaner if injectors are suspected.

P0420 – Catalyst System Efficiency Below Threshold

This means the catalytic converter isn’t reducing emissions effectively. Possible causes:

• Failing catalytic converter
• Faulty oxygen sensors (upstream or downstream)
• Engine running rich (too much fuel)

Check oxygen sensor readings first. If they’re out of range, replace them. If the converter is damaged, replacement may be necessary.

P0171 – System Too Lean (Bank 1)

The engine is receiving too much air or too little fuel. Causes include:

• Vacuum leaks (cracked hoses, intake manifold gasket)
• Dirty or faulty MAF sensor
• Weak fuel pump or clogged fuel filter

Inspect all vacuum lines and clean the MAF sensor with a specialized spray. If the problem persists, test fuel pressure.

P0440 – Evaporative Emission Control System Malfunction

This relates to the fuel vapor system. Common issues:

• Loose or damaged gas cap
• Leaking EVAP hoses
• Faulty purge valve

Start by tightening or replacing the gas cap. If the light returns, inspect the EVAP system for leaks.

P0700 – Transmission Control System Malfunction

This is a general code indicating a transmission issue. It often triggers additional codes (P0715, P0720, etc.). Causes may include:

• Low transmission fluid
• Faulty solenoids
• Worn clutch packs

Check fluid level and condition. If low, top it off and look for leaks. For internal issues, consult a transmission specialist.

Troubleshooting Tips for Infiniti Owners

Even with the right tools, diagnosing engine codes can be tricky. Here are some practical tips to help you get accurate results.

1. Don’t Ignore Pending Codes

Some scanners show “pending” codes—issues that haven’t yet triggered the service engine light. These can give you early warning of developing problems. Address them before they become serious.

2. Check for Technical Service Bulletins (TSBs)

Infiniti may have issued TSBs for known issues related to your code. These are free advisories from the manufacturer. Search online using your VIN and the code number.

3. Use Freeze Frame Data

Freeze frame data shows the engine conditions (RPM, speed, temperature) when the code was set. This helps determine if the issue occurs at idle, under load, or during acceleration.

4. Test Drive After Repairs

After fixing the issue, take your Infiniti for a test drive under various conditions (city, highway, hills). This helps ensure the problem is truly resolved and prevents the light from coming back.

5. Keep a Maintenance Log

Document every code, repair, and part replacement. Over time, this log can reveal patterns—like recurring misfires or sensor failures—and help you anticipate future needs.

When to See a Professional

While many service engine light issues can be resolved at home, some require expert attention. Seek professional help if:

• The code points to transmission, ABS, or airbag systems
• You’re unsure how to perform the repair safely
• The light flashes (indicating a severe misfire that can damage the catalytic converter)
• Multiple codes appear simultaneously
• The problem returns after DIY repairs

Infiniti dealerships and certified repair shops have advanced diagnostic tools and access to factory service information. They can also perform software updates and calibrations that consumer scanners can’t.

Conclusion

Checking service engine light codes on your Infiniti doesn’t have to be intimidating. With an OBD2 scanner, a little patience, and this guide, you can diagnose issues quickly and accurately. Whether you’re dealing with a simple gas cap problem or a more complex engine fault, understanding the codes empowers you to make informed decisions about repairs.

In 2026, technology makes it easier than ever to stay on top of your vehicle’s health. Invest in a reliable scanner, learn the common codes, and don’t hesitate to seek help when needed. Your Infiniti will thank you with better performance, improved fuel economy, and fewer unexpected breakdowns.

Remember: the service engine light is your car’s way of communicating. Listen to it, act promptly, and keep driving with confidence.