Tired of paying a dealer just to clear a check engine light? You’re not alone. With a proper diesel diagnostic kit, many common trouble codes can be identified — and cleared — by you, without a trip to the shop.

1. P2002 – DPF Efficiency Below Threshold

What it means: The diesel particulate filter (DPF) is not working efficiently.
How to fix it: Use your diagnostic laptop to perform a forced regen. Often, that’s all it needs.

2. P0401 – EGR Flow Insufficient

What it means: Your exhaust gas recirculation system is clogged or not operating.
How to fix it: Run an EGR test through your scanner. In some cases, a software reset clears the code after cleaning.

3. P2459 – DPF Regeneration Too Frequent

What it means: Your truck is regenerating too often, indicating incomplete cycles.
How to fix it: Clear the code, perform a manual regen, and inspect for upstream issues like turbo leaks or faulty sensors.

4. SPN 5246/FMI 0 – SCR/DEF System Derate

What it means: The DEF system is restricting engine power due to missed regens or sensor faults.
How to fix it: Reset the SCR system using dealer software like Universal Diagnostics, Diesel Tech, DDL.

5. SPN 3251 – Engine Derate Due to Aftertreatment

What it means: Emissions system triggered a limp mode.
How to fix it: Use your laptop to clear codes, check DEF levels, and perform a reset. Don't wait — this one can shut down your truck.

top Paying for Dealer Resets

With NoFeeDiesel’s diagnostic laptop kits, you can:

• Read and clear fault codes

• Perform regens and resets

• Save hundreds per month in dealer labor

• Work on Class 3–8 trucks and off-highway gear

Own your diagnostics. Skip the subscription.

Shop diesel diagnostic kits now