If your diesel truck has triggered a check engine light (CEL), don’t panic. This warning is your truck’s way of telling you something’s out of range—but it doesn’t always mean you have a major problem. In this blog, we’ll explain how to reset your check engine light safely and what tools you’ll need to do it right.
What Is a Check Engine Light?
The check engine light (CEL), sometimes called a malfunction indicator lamp (MIL), illuminates when your truck’s ECU (Engine Control Unit) detects a fault. This could be caused by emissions issues, fuel problems, electrical malfunctions, or sensor failures.
Ignoring this light could result in lower fuel economy, reduced power, or further damage to your engine.
Step-by-Step: How to Reset the Check Engine Light
Here’s how you can reset the light the right way:
1. Connect a Diesel Diagnostic Scanner
Use a professional-grade diagnostic laptop with built-in software like Diesel Tech or Universal Diesel. This allows you to read the fault codes and identify what caused the warning in the first place.
2. Read & Record All Active Fault Codes
Before clearing anything, record the fault codes. This ensures you have a record of the issue in case it reappears. Some faults are intermittent, while others are precursors to larger problems.
3. Address the Underlying Problem
Do not clear the codes without understanding or repairing the cause. Fault codes exist to warn you. Only after resolving the problem should you proceed to the next step.
4. Clear the Codes
Using your scanner, select “Clear Active Faults” or “Reset MIL.” The check engine light should turn off if there are no remaining issues.
5. Test Drive Your Truck
After resetting, take the vehicle for a test drive. If the CEL returns quickly, you may still have an unresolved issue.
Tools You’ll Need
You don’t need to be a full-time mechanic to clear codes—just the right tools.
✅ Rugged Diagnostic Laptop
✅ OEM-Ready Scanner (like those sold by DieselScanners.com)
✅ J1939 or OBD-II Cable
✅ Fault Code Reference Chart (included in our kits)
When Not to Clear the Light
If your truck is experiencing:
-
Loss of power
-
DPF issues
-
High fuel consumption
-
Regeneration failure
…you should never just clear the light. You must diagnose and repair first—or risk damaging the engine or emissions system.
Final Thoughts
The check engine light doesn’t have to be a headache. With the right tools and a little know-how, you can identify, address, and clear most issues on your own. Our diesel laptop kits come preloaded with everything you need to handle fault codes like a pro.
🛠 Ready to take control?
Shop full diesel scanner kits now → DieselScanners.com