If your 2017 Ford Mustang’s check engine light is on, don’t panic—getting the trouble codes is easier than you think. With the right tools and a few simple steps, you can read the diagnostic trouble codes (DTCs) yourself, understand what they mean, and decide whether it’s a quick fix or time to visit a mechanic.
Key Takeaways
- Use an OBD2 scanner: This is the fastest and most reliable way to retrieve codes from your 17 Mustang’s onboard computer.
- Locate the OBD2 port: It’s usually under the dashboard on the driver’s side, near the steering column.
- Understand code formats: Codes like P0300 or P0171 follow a standard pattern—first letter indicates system, numbers specify the issue.
- Don’t ignore pending codes: Even if the light isn’t on, stored or pending codes can reveal early warnings.
- Clear codes carefully: Only reset the system after diagnosing and fixing the problem to avoid masking serious issues.
- Freeze frame data helps: Most scanners show engine conditions when the fault occurred—use this to pinpoint the cause.
- Know when to seek help: Some codes require professional tools or expertise—don’t hesitate to consult a technician.
📑 Table of Contents
Why Is My 17 Mustang Check Engine Light On?
So, you’re driving your sleek 2017 Ford Mustang—maybe cruising down the highway or just heading to work—and suddenly, that little orange engine icon pops up on your dashboard. Your heart skips a beat. Is it serious? Will it cost a fortune? Can you fix it yourself?
First things first: don’t panic. The check engine light (CEL) is your car’s way of saying, “Hey, something’s not quite right.” It could be as minor as a loose gas cap or as serious as a misfiring engine. But here’s the good news—your Mustang is equipped with an advanced onboard diagnostic system (OBD2) that stores specific trouble codes whenever a problem is detected. These codes are like a secret language your car uses to tell you exactly what’s going on.
The 2017 Mustang, whether it’s the EcoBoost, GT, or even the Shelby variant, uses the same OBD2 protocol as most modern vehicles. That means you can access these codes with the right tool—no need to rush to the dealership right away. In fact, many common issues can be diagnosed and even fixed at home with a little know-how and the right equipment.
Common Reasons the Light Comes On
Let’s break down some of the most frequent culprits behind the 17 Mustang check engine light:
- Loose or faulty gas cap: This is the #1 cause of a CEL in Mustangs. If the cap isn’t sealed properly, fuel vapors can escape, triggering a P0455 or similar code.
- Oxygen (O2) sensor failure: These sensors monitor exhaust gases and help the engine adjust the air-fuel mixture. A bad O2 sensor can hurt fuel economy and performance.
- Mass airflow (MAF) sensor issues: The MAF measures how much air enters the engine. Dirt or malfunction can cause rough idling or hesitation.
- Spark plug or ignition coil problems: Misfires (like code P0300) often stem from worn spark plugs or failing coils—common in high-performance engines.
- Catalytic converter inefficiency: Over time, the catalytic converter can clog or degrade, leading to reduced performance and increased emissions.
- Evaporative emissions (EVAP) system leaks: Small leaks in the fuel vapor system can trigger codes like P0442 or P0456.
The key takeaway? Most of these issues are detectable early if you know how to read the codes. And that’s exactly what we’re going to teach you.
How to Get Codes from Your 17 Mustang
Visual guide about 17 Mustang Check Engine Light How to Get Codes
Image source: mustang7g.com
Now that you know why the light might be on, let’s get to the main event: how to actually retrieve those diagnostic trouble codes (DTCs) from your Mustang’s computer.
There are two main ways to do this: using an OBD2 scanner or, in some cases, using the car’s built-in system (though this method is limited). For most Mustang owners, an OBD2 scanner is the best bet—it’s fast, accurate, and gives you detailed information.
Step 1: Locate the OBD2 Port
The OBD2 port is a 16-pin connector that allows communication between your car’s computer and external devices. In the 2017 Mustang, it’s typically located under the dashboard on the driver’s side, just below the steering wheel. You might need to crouch down a bit to see it—it’s usually black or gray and shaped like a trapezoid.
If you can’t find it, check behind a small cover or panel. Some Mustangs have it tucked behind the fuse box cover or near the parking brake. Once you locate it, make sure it’s clean and free of debris.
Step 2: Choose the Right OBD2 Scanner
Not all scanners are created equal. Here’s what to look for:
- Basic code readers: These are inexpensive (under $30) and great for reading and clearing codes. Perfect for beginners.
- Bluetooth/Wi-Fi scanners: These connect to your smartphone via an app (like Torque Pro or OBD Fusion). They offer real-time data, graphs, and more detailed diagnostics.
- Professional-grade scanners: These are used by mechanics and offer advanced features like live data streaming, bi-directional controls, and module programming. Overkill for most DIYers, but useful if you’re serious about car maintenance.
For most Mustang owners, a mid-range Bluetooth scanner (like the BlueDriver or FIXD) offers the best balance of price, features, and ease of use.
Step 3: Plug In and Power On
Once you’ve got your scanner, here’s how to use it:
- Turn off the ignition.
- Plug the OBD2 scanner into the port.
- Turn the ignition to the “ON” position (don’t start the engine yet).
- Wait for the scanner to power up and connect to the car’s computer.
- Follow the on-screen prompts to read the codes.
Most scanners will display a list of stored trouble codes. Some may also show “pending” codes—these are issues the computer has detected but hasn’t confirmed yet. Pending codes can be useful for catching problems early.
Step 4: Record and Interpret the Codes
Once you’ve retrieved the codes, write them down. They usually look something like P0301, P0171, or P0420. Each code follows a standard format:
- P: Powertrain (engine, transmission, emissions)
- B: Body (airbags, climate control, etc.)
- C: Chassis (ABS, suspension)
- U: Network/communication (CAN bus issues)
The first digit after the letter indicates whether it’s a generic (0) or manufacturer-specific (1) code. The next digits narrow down the system and component.
For example:
– P0300: Random/multiple cylinder misfire detected
– P0171: System too lean (Bank 1)
– P0420: Catalyst system efficiency below threshold (Bank 1)
You can look up these codes online using free resources like OBD-Codes.com or the scanner’s built-in database.
Using Your Smartphone to Read Codes
If you’re tech-savvy, you might prefer using your smartphone to read the codes. Bluetooth OBD2 scanners make this easy and add a lot of functionality.
How It Works
A Bluetooth OBD2 scanner plugs into the port just like a regular scanner, but instead of a built-in screen, it sends data to your phone via Bluetooth. You’ll need to download a compatible app—popular choices include:
- Torque Pro (Android): Highly customizable, supports live data, graphs, and custom dashboards.
- OBD Fusion (iOS/Android): User-friendly interface, great for beginners and pros alike.
- FIXD (iOS/Android): Designed for non-experts, explains codes in plain English and estimates repair costs.
Once the app is installed and paired with the scanner, you can read codes, view real-time engine data (like RPM, coolant temp, and fuel trim), and even log trips.
Benefits of Using an App
Why go digital? Here are a few advantages:
- Real-time monitoring: See how your engine is performing as you drive.
- Historical data: Track changes over time to spot trends.
- Alerts and reminders: Some apps notify you when a new code appears or when maintenance is due.
- Shareability: Easily email or text codes to a mechanic for a second opinion.
Just remember: your phone needs to be nearby for the Bluetooth connection to work. And don’t use the app while driving—pull over first!
Understanding What the Codes Mean
Reading the code is only half the battle. The real challenge is understanding what it means and what to do about it.
Generic vs. Manufacturer-Specific Codes
As mentioned earlier, codes starting with “P0” are generic and apply to all vehicles. Codes starting with “P1” are often manufacturer-specific—meaning Ford may have assigned a unique meaning to that code.
For example, P1131 in a Mustang might refer to a specific oxygen sensor issue that’s different from the same code in a Toyota. Always double-check with a reliable source or your Mustang’s service manual.
Freeze Frame Data: Your Best Friend
One of the most powerful features of modern OBD2 scanners is freeze frame data. This captures the engine’s operating conditions at the exact moment a fault was detected.
Freeze frame data includes:
– Engine RPM
– Vehicle speed
– Coolant temperature
– Load value
– Fuel trim levels
This information can help you recreate the conditions that caused the problem. For instance, if the code appeared when the engine was cold and at idle, it might point to a vacuum leak or idle air control issue.
Common 17 Mustang Codes and What They Mean
Here are a few codes you might encounter in your 2017 Mustang:
- P0300 – Random/Multiple Cylinder Misfire: Could be spark plugs, coils, fuel injectors, or even low compression. Check ignition components first.
- P0171 – System Too Lean (Bank 1): Often caused by a vacuum leak, dirty MAF sensor, or faulty O2 sensor. Inspect intake hoses and clean the MAF.
- P0420 – Catalyst Efficiency Below Threshold: Usually means the catalytic converter is failing. Can also be triggered by a bad O2 sensor.
- P0455 – Large EVAP Leak: Likely a loose gas cap or cracked hose in the evaporative system. Start by tightening the cap.
- P0128 – Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature): The engine isn’t reaching normal operating temperature—could be a stuck-open thermostat.
Always research the specific code and consider the context. For example, a P0300 code after a cold start might be normal in some conditions, but if it happens frequently, it’s a red flag.
When to Clear the Codes—and When Not To
Once you’ve diagnosed the issue, you might be tempted to clear the codes and see if the light stays off. But timing is everything.
Clear Codes After Fixing the Problem
Only clear the codes after you’ve addressed the root cause. If you clear them too soon, you won’t know if your fix worked. For example, if you tightened the gas cap and cleared the P0455 code, wait a few drive cycles to see if it returns.
Most scanners have a “Clear Codes” or “Reset” button. Use it sparingly and only when you’re confident the issue is resolved.
Don’t Clear Codes Before a Mechanic Visit
If you’re planning to take your Mustang to a shop, leave the codes intact. Mechanics rely on them to diagnose problems quickly. Clearing the codes erases valuable diagnostic data.
What If the Light Comes Back On?
If the check engine light returns after clearing the codes, it means the problem wasn’t fully resolved. The computer has detected the same (or a new) issue. Re-scan and investigate further.
Sometimes, a code might reappear even after a proper fix—this could be due to a slow sensor response or intermittent wiring issue. In such cases, monitoring the car over several days is wise.
DIY Fixes vs. When to Call a Mechanic
Now that you know how to get the codes, the next question is: can you fix it yourself?
Easy DIY Fixes
Some issues are simple and safe to handle at home:
- Tightening or replacing the gas cap: Costs under $20 and takes 2 minutes.
- Cleaning the MAF sensor: Use MAF cleaner spray—no disassembly needed.
- Replacing spark plugs: Doable with basic tools if you have access to the engine bay.
- Checking for vacuum leaks: Listen for hissing sounds or use a smoke machine (or even a spray bottle with soapy water).
These tasks require minimal mechanical skill and can save you hundreds in labor costs.
When to Seek Professional Help
However, some problems are best left to the experts:
- Internal engine issues: Like low compression or timing problems—require specialized tools and knowledge.
- Transmission faults: Codes related to the transmission (like P0700) often need a mechanic with Ford-specific equipment.
- Electrical gremlins: Intermittent wiring or sensor issues can be tricky to trace.
- Emissions system repairs: Replacing a catalytic converter or EGR valve may require lifting the car and dealing with exhaust components.
If you’re unsure, it’s always better to consult a trusted mechanic. Many shops offer free code reads—use that to your advantage.
Preventing Future Check Engine Light Issues
An ounce of prevention is worth a pound of cure. Here’s how to keep your 17 Mustang running smoothly and avoid unnecessary CEL scares.
Regular Maintenance
Follow the maintenance schedule in your owner’s manual. Key items include:
– Oil and filter changes (every 5,000–7,500 miles)
– Spark plug replacement (every 60,000–100,000 miles, depending on engine)
– Air filter replacement (every 15,000–30,000 miles)
– Fuel system cleaning (every 30,000 miles)
Use Quality Fuel and Additives
Fill up at reputable stations and consider using a fuel system cleaner every few tanks. This helps prevent carbon buildup and keeps injectors clean.
Inspect Hoses and Connections
Periodically check vacuum hoses, intake ducts, and electrical connectors for cracks, leaks, or loose fits. A small leak can trigger big problems.
Listen to Your Car
Unusual noises, vibrations, or performance changes are early warning signs. Address them before they trigger a code.
Conclusion
Dealing with the 17 Mustang check engine light doesn’t have to be stressful. With the right tools and a little knowledge, you can read the codes, understand what they mean, and take action—whether that’s a quick DIY fix or a trip to the shop.
Remember: the check engine light is your car’s way of communicating. Ignoring it can lead to bigger, costlier problems down the road. But by learning how to get the codes and respond appropriately, you’ll save money, extend your Mustang’s life, and drive with confidence.
So grab an OBD2 scanner, plug it in, and take control of your car’s health. Your 2017 Mustang deserves it.
Frequently Asked Questions
Can I read the check engine light codes without a scanner?
Yes, but it’s limited. Some older methods involve counting dashboard light flashes, but the 2017 Mustang doesn’t support this. An OBD2 scanner is the most reliable way to get accurate codes.
How much does an OBD2 scanner cost?
Basic code readers start around $20, while Bluetooth models range from $50 to $100. Professional scanners can cost hundreds, but most Mustang owners only need a mid-range device.
Will clearing the codes fix the problem?
No, clearing codes only resets the system. The underlying issue must be repaired first. Otherwise, the light will likely come back on.
Can a loose gas cap really trigger the check engine light?
Absolutely. A loose or damaged gas cap is one of the most common causes of a CEL in the 17 Mustang. Always check it first—it’s free and takes seconds.
How often should I scan my Mustang for codes?
There’s no need to scan regularly unless the light is on. However, scanning after major repairs or long trips can help catch issues early.
What if my scanner shows “No Codes” but the light is on?
This could mean the scanner isn’t compatible, the port has power issues, or the light was triggered by a temporary glitch. Try a different scanner or have a mechanic check the system.