Discover how to read engine light codes on your Infiniti G35 using simple tools or manual methods. This guide covers OBD2 scanners, error code meanings, and next steps for repairs in 2026.
Key Takeaways
- Use an OBD2 scanner: The easiest and most accurate way to read engine codes on your Infiniti G35 is with a compatible OBD2 scanner, available at most auto parts stores or online.
- Manual code reading is possible: If you don’t have a scanner, you can retrieve trouble codes manually using the G35’s onboard diagnostic system and the check engine light flashes.
- Understand common G35 codes: Frequent issues include P0420 (catalytic converter), P0171 (lean fuel mixture), and P0300 (random misfire)—knowing these helps prioritize repairs.
- Clear codes after repairs: Always clear the codes after fixing the issue to reset the system and confirm the problem is resolved.
- Don’t ignore the light: Even if the car runs fine, a check engine light can signal hidden problems that may worsen over time.
- Use updated tools in 2026: Modern OBD2 scanners now support enhanced diagnostics, live data, and smartphone integration for better troubleshooting.
- Consult a mechanic if unsure: Some codes require professional diagnosis—don’t hesitate to seek expert help for complex issues.
How to Check Engine Light Codes Infiniti G35
If you own an Infiniti G35, you know it’s a reliable, sporty sedan that blends performance with comfort. But like any vehicle, it’s not immune to mechanical hiccups. One of the most common—and sometimes alarming—signs something might be off is the check engine light. Whether it’s flashing or steady, this little orange icon on your dashboard is your car’s way of saying, “Hey, I need attention.”
In this guide, we’ll walk you through exactly how to check engine light codes on your Infiniti G35 in 2026. Whether you’re a DIY enthusiast or just want to understand what’s going on under the hood, you’ll learn how to read trouble codes, interpret them, and take the right next steps. We’ll cover both modern OBD2 scanner methods and the old-school manual technique—perfect if you don’t have a scanner handy.
By the end of this guide, you’ll be able to confidently diagnose common issues, save money on diagnostics, and keep your G35 running smoothly for years to come.
What Is the Check Engine Light?
The check engine light, also known as the malfunction indicator lamp (MIL), is part of your car’s onboard diagnostics system (OBD2). When the engine control unit (ECU) detects a problem with the engine, emissions, or related systems, it triggers this light to alert you.
There are two types of check engine light signals:
- Steady light: Indicates a non-urgent issue that should be checked soon, like a loose gas cap or minor sensor fault.
- Flashing light: Signals a serious problem, such as a misfire that could damage the catalytic converter. If the light is flashing, pull over safely and avoid driving until the issue is resolved.
Ignoring the light—especially a flashing one—can lead to expensive repairs down the road. That’s why it’s important to check the codes as soon as possible.
Why Check Engine Codes Matter on the Infiniti G35
The Infiniti G35, produced from 2003 to 2006, uses the OBD2 system, which became standard in all vehicles after 1996. This means every G35 can communicate diagnostic trouble codes (DTCs) through a universal port.
Checking these codes helps you:
- Identify the root cause of performance issues
- Prevent further damage to the engine or emissions system
- Save money by avoiding unnecessary repairs
- Prepare for emissions testing
- Maintain your car’s resale value
In 2026, with advancements in automotive technology, diagnosing your G35 is easier than ever. Even if your car is over 20 years old, modern tools and resources make it simple to stay on top of maintenance.
Tools You’ll Need to Read Engine Codes
Before you start, gather the right tools. Here’s what you’ll need:
1. OBD2 Scanner (Recommended)
The most reliable way to read codes is with an OBD2 scanner. These devices plug into your car’s diagnostic port and display trouble codes on a screen. In 2026, scanners range from basic $20 models to advanced Bluetooth units that connect to your smartphone.
Visual guide about How to Check Engine Light Codes Infiniti G35
Image source: youcanic.com
Look for scanners that support:
- Full OBD2 protocol compatibility
- Live data streaming
- Code definitions (not just numbers)
- Ability to clear codes
Popular brands include BlueDriver, Innova, and Autel. Many auto parts stores also offer free code reading if you don’t want to buy a scanner.
2. Paperclip or Jumper Wire (For Manual Reading)
If you don’t have a scanner, you can still read codes manually using the G35’s onboard system. This method uses the check engine light to flash in patterns that correspond to specific codes. You’ll need a simple paperclip or jumper wire to bridge two terminals in the diagnostic port.
3. Owner’s Manual
Your Infiniti G35 owner’s manual contains useful information about the OBD2 system and warning lights. Keep it handy for reference.
4. Smartphone (Optional)
If you use a Bluetooth OBD2 scanner, download a compatible app like Torque Pro (Android) or OBD Fusion (iOS). These apps provide detailed diagnostics, graphs, and code explanations.
Step-by-Step: How to Read Codes with an OBD2 Scanner
Using an OBD2 scanner is the fastest and most accurate method. Follow these steps:
Step 1: Locate the OBD2 Port
The OBD2 port in the Infiniti G35 is located under the dashboard on the driver’s side, near the steering column. It’s a 16-pin connector, usually black or gray, and easy to spot. You may need to crouch down or use a flashlight to see it clearly.
Step 2: Turn the Ignition to “On”
Insert your key and turn it to the “On” position (but don’t start the engine). This powers up the car’s electrical system and allows the scanner to communicate with the ECU.
Step 3: Plug in the Scanner
Connect your OBD2 scanner to the port. Make sure it’s firmly seated. Most scanners will power on automatically when plugged in.
Step 4: Follow the Scanner’s Instructions
Turn on the scanner and follow the on-screen prompts. Most devices will ask you to:
- Select your vehicle make (Infiniti)
- Choose the model year (2003–2006)
- Confirm engine type (V6 3.5L)
Once connected, the scanner will retrieve any stored trouble codes.
Step 5: Read the Codes
The scanner will display one or more codes, such as P0420 or P0171. These are five-character alphanumeric codes:
- P = Powertrain (engine/transmission)
- 0 = Generic code (standard across all vehicles)
- 420 = Specific fault identifier
Write down all the codes you see. Even if the light is off, pending codes may still be stored.
Step 6: Interpret the Codes
Use the scanner’s built-in database or search online for code definitions. For example:
- P0420: Catalyst system efficiency below threshold (Bank 1)
- P0171: System too lean (Bank 1)
- P0300: Random/multiple cylinder misfire detected
Understanding what each code means helps you decide whether to fix it yourself or visit a mechanic.
Step 7: Clear the Codes (After Repair)
Once the issue is fixed, use the scanner to clear the codes. This resets the check engine light and allows you to see if the problem returns. If the light comes back on, the issue may not be fully resolved.
How to Read Codes Manually (Without a Scanner)
If you don’t have an OBD2 scanner, you can still retrieve codes using the manual method. This technique uses the check engine light to flash in sequences that represent trouble codes.
Step 1: Locate the Diagnostic Connector
Find the OBD2 port under the dashboard (same as above). Look for two specific pins: Pin 4 (Ground) and Pin 12 (Diagnostic Request). These are usually labeled or shown in your owner’s manual.
Step 2: Bridge the Pins
Straighten a paperclip or use a jumper wire. Insert one end into Pin 4 and the other into Pin 12. This creates a circuit that tells the ECU to output codes via the check engine light.
Step 3: Turn the Ignition to “On”
Turn the key to the “On” position (engine off). The check engine light should begin to flash.
Step 4: Count the Flashes
The light will flash in patterns:
- Long flashes = tens digit
- Short flashes = ones digit
For example, two long flashes followed by three short flashes = Code 23.
Step 5: Record All Codes
The system will cycle through all stored codes. Write them down. A long pause between codes indicates the end of the sequence.
Step 6: Look Up the Codes
Use an online OBD2 code database or repair manual to interpret the numbers. Note: Manual reading only shows generic P0 codes, not manufacturer-specific ones.
Step 7: Clear the Codes
To reset the system, disconnect the battery for 10–15 minutes. This clears the ECU’s memory. Reconnect the battery and check if the light returns.
Common Infiniti G35 Engine Codes and What They Mean
Here are some of the most frequent trouble codes on the G35 and what they typically indicate:
P0420 – Catalyst System Efficiency Below Threshold
This is one of the most common codes on the G35. It means the catalytic converter isn’t cleaning exhaust gases as well as it should. Causes include:
- Failing catalytic converter
- Oxygen sensor malfunction
- Exhaust leaks
- Rich or lean fuel mixture
Tip: Before replacing the catalytic converter (which is expensive), check the oxygen sensors and exhaust system for leaks.
P0171 – System Too Lean (Bank 1)
This code indicates the engine is running with too much air and not enough fuel. Possible causes:
- Vacuum leaks (cracked hoses, intake manifold gasket)
- Faulty mass airflow (MAF) sensor
- Weak fuel pump or clogged fuel filter
- Dirty fuel injectors
Tip: Inspect all vacuum lines for cracks or disconnections. Clean the MAF sensor with MAF cleaner spray.
P0300 – Random/Multiple Cylinder Misfire
A misfire means one or more cylinders aren’t firing properly. This can cause rough idle, loss of power, and increased emissions. Causes include:
- Worn spark plugs or ignition coils
- Low fuel pressure
- Compression issues
- Faulty fuel injectors
Tip: Replace spark plugs and coils if they’re over 60,000 miles old. Use OEM or high-quality aftermarket parts.
P0133 – O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
This code points to a slow-responding upstream oxygen sensor. The O2 sensor monitors exhaust gases and helps the ECU adjust the fuel mixture. A faulty sensor can reduce fuel economy and increase emissions.
P0440 – Evaporative Emission Control System Malfunction
This relates to the fuel vapor system, which captures gasoline fumes. Common causes:
- Loose or missing gas cap
- Leaking EVAP hose
- Faulty purge valve
Tip: Always check the gas cap first—it’s the easiest and cheapest fix.
Troubleshooting Tips for Accurate Diagnosis
Reading the code is just the first step. To avoid misdiagnosis, follow these best practices:
1. Don’t Assume the Code Tells the Whole Story
A code like P0420 doesn’t always mean the catalytic converter is bad. It could be triggered by a bad O2 sensor or exhaust leak. Always investigate further before replacing parts.
2. Check for Multiple Codes
Sometimes one problem causes several codes. For example, a vacuum leak might trigger P0171, P0300, and P0420. Fix the root cause first.
3. Use Live Data
If your scanner supports live data, monitor sensor readings like:
- Short-term and long-term fuel trims
- O2 sensor voltage
- Engine load and RPM
Abnormal values can confirm or rule out suspected issues.
4. Inspect Visually
Look for obvious problems: cracked hoses, loose wires, oil leaks, or damaged components. Sometimes the fix is simpler than you think.
5. Clear Codes and Test Drive
After making repairs, clear the codes and drive the car for a few days. If the light returns, the problem may still exist.
When to See a Mechanic
While many G35 issues can be DIY-fixed, some require professional help. See a mechanic if:
- The check engine light is flashing
- You’re getting multiple complex codes
- The car is running poorly or overheating
- You suspect internal engine damage
- You’re not comfortable performing repairs
In 2026, many mechanics use advanced diagnostic tools that can read manufacturer-specific codes and perform system tests not available to consumer scanners.
Preventing Future Check Engine Light Issues
The best way to avoid check engine lights is through regular maintenance:
- Change oil and filter every 5,000 miles
- Replace spark plugs every 60,000 miles
- Inspect and replace air and fuel filters as needed
- Use quality fuel and additives occasionally
- Check tire pressure and alignment
- Keep the gas cap tight
A well-maintained G35 can easily reach 200,000 miles or more.
Conclusion
Checking engine light codes on your Infiniti G35 doesn’t have to be intimidating. Whether you use a modern OBD2 scanner or the manual flash method, you can quickly identify what’s causing the warning light and take action. In 2026, with better tools and more online resources than ever, diagnosing your G35 is easier and more accurate.
Remember: the check engine light is your car’s way of communicating. Don’t ignore it. By learning how to read and interpret trouble codes, you’ll save money, extend your car’s life, and drive with confidence.
Start with the basics—locate the OBD2 port, retrieve the codes, and research their meanings. With a little knowledge and the right tools, you’ll keep your Infiniti G35 running strong for years to come.