Fault code details

Quickly discover what those dash lights mean and know what caused the problem.

Live data monitoring

Viewing live data keeps you informed about your vehicle at any moment.

Bi-directional commands

Reset fault codes, reset aftertreatment, forced DPF regen

Instant fault code insights for Detroit Diesel engines

  • Understand your Check Engine Light: Quickly understand what those active fault codes mean with detailed information to help you know what is going on.
  • Identify the cause and take action: Get detailed explanations of fault codes specific to Detroit Diesel engines. You can use this information know what to do and how to proceed.
  • Track how many times that fault occurred: You will see the count and be able to use that information to track if this is the first time this issue is coming on or it's an ongoing issue.
  • It doesn't just cover your engine: You will notice we cover transmission, abs, chassis, cab & body as well. We try to report to you everything that is going on with your vehicle.
Learn More about fault codes

Monitor real-time data engine parameters

What you can monitor:

  • Intake pressure (turbo boost): Monitor turbocharger performance to gauge how your engine responds under various load conditions.
  • DPF soot and ash levels: Monitor the accumulation of soot and ash to determine the optimal times for DPF regen, helping prevent DPF derates.
  • DEF fluid level: Keep track of Diesel Exhaust Fluid levels.
  • EGR valve position: Track the position of the Exhaust Gas Recirculation valve.
  • Exhaust and DPF temperatures: Observe temperatures to manage the DPF Regen process effectively.
  • SCR temperatures: Keep an eye on Selective Catalytic Reduction temperatures to ensure NOx reduction.
  • Engine mileage & hours: Track engine hours and other vital diagnostics.
  • + more: We go even beyond this list. Our goal is to supply you with data to help you monitor your vehicle in real time.
Learn More about live data

Detroit Diesel | Years and engines covered

Reset fault codes

Resetting fault codes: The reset of fault codes covers both active and Inactive codes.

  • Active codes: These are alerts for current issues that need immediate attention.
  • Inactive codes: These are records of past problems. They’re helpful for spotting patterns or issues that might come back again.
  • Reset all modules: We perform the reset on all the available modules that we are connected to, including transmission, body, cab & chassis systems. 

Importance of resetting codes: Clearing these codes after you fix an issue keeps the diagnostic system focused only on what’s currently active. This is crucial for verifying that repairs were successful and for maintaining accurate, up-to-date vehicle diagnostics.

Reset ash accumulator and DPF zone levels

This command is used to reset stored ash levels and soot severity indicators in the Diesel Particulate Filter (DPF) system's control modules (MCM/CPC/ACM).

When to use:

  • Reset DPF ash accumulators: Clears logged ash content from the engine control module to maintain filter performance.
  • Reset DPF zone levels: Updates soot level readings in the control modules to accurately reflect current conditions.

Addressed fault codes:

  • SPN 247 FMI 14, SPN 3719 FMI 0, SPN 3720 FMIs 15 and 16


  • Ensures accuracy: Keeps DPF system readings accurate, essential for effective operation.
  • Avoids unnecessary maintenance: Prevents premature maintenance actions based on incorrect data.
  • Maintains efficiency: Helps the DPF operate efficiently and meet emission standards.

Using this command as needed ensures optimal functionality of the DPF, enhancing vehicle performance and compliance with emissions regulations.

Reset SCR accumulator

This command resets the stored Diesel Exhaust Fluid (DEF) related values in the aftertreatment control module (ACM). It is specifically performed after replacing the SCR Catalyst, commonly referred to as the 1-Box.

When to use:

  • After SCR catalyst replacement: Ensures that the ACM accurately reflects the new catalyst’s characteristics and conditions.


  • Ensures system accuracy: Resets DEF usage and storage data to match the new catalyst, essential for proper SCR function.
  • Maintains system efficiency: Helps the SCR system efficiently reduce emissions by ensuring it operates with correct data post-replacement.
  • Prevents malfunctions: Avoids potential issues related to incorrect DEF data which can lead to improper SCR performance and increased emissions.

Using this command after replacing the SCR Catalyst ensures that the vehicle's emission control system continues to function efficiently and comply with emissions standards.

Forced DPF regen

The Diesel Particulate Filter (DPF) captures soot during engine operation. To clear this soot, the DPF periodically undergoes active or passive regen, usually automatically, while the engine runs.

When to use:

  • Fault codes: Some fault codes require you to run a forced DPF regen in order for certain fault codes to clear. This is because the emission system wants to run through all the system checks before the fault codes is cleared.
  • Driving conditions: If regular driving doesn't achieve the engine load and temperature necessary for active regen, then a forced DPF regen becomes essential. This is often required in situations involving excessive idling or operations under light loads.
  • High soot: If soot accumulation surpasses what normal regeneration can handle, a forced DPF regen is necessary to prevent blockages.


  • Ensures efficiency & reliability: It maintains the DPF’s effectiveness and extends its lifespan.

Forced SCR Efficiency regen

Forced SCR (Selective Catalytic Reduction) regeneration is crucial when certain fault codes indicate inefficiencies in the SCR system. This procedure, also known as the “Parked SCR Efficiency Test,” assesses the NOx (Nitrogen Oxides) conversion efficiency using the inlet and outlet NOx sensors.

When to use:

  • Specific fault codes: Conduct this test when fault codes related to SCR Efficiency regeneration are active, indicating issues with NOx conversion.

Common causes triggering the test:

  • Contaminated DEF (Diesel Exhaust Fluid)
  • Incorrect urea concentration in DEF
  • Biased NOx sensors
  • Excessive DEF build-up in the exhaust
  • Failure of the integrated 1-Box system


  • Restores SCR efficiency: Ensures the SCR system is correctly converting NOx, crucial for optimal emission control.
  • Prevents further damage: Addresses underlying issues before they lead to more severe problems in the emission system.

Forced SCR regeneration is essential for maintaining the functionality and efficiency of the emission control system, especially after detecting specific fault issues.

Nexiq Blue-Link 2 Hardware

  • Unlock the full potential of your truck's diagnostics system with Nexiq Blue-Link 2 hardware.
  • Designed for seamless integration with the trucks we support, this device connects via Bluetooth, ensuring robust and reliable data transmission without the hassle of wires.
Learn more about hardware
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This product paid for itself on the first use. Easy to use and understand, and prevents small problems from turning into bigger problems. My favorite feature is the "Live Data". OTR Performance is a must have for any smart O/O or small fleet who wants to save time and money.
— Robert Purser - Google Review
Money well spent!! Their customer service is excellent and the diagnostic subscription is gonna save you money. Thoroughly impressed! Just imagine being able to get to a shop after you disable the derate that has you stuck on the shoulder of the highway, needing a tow for thousands.
— Calcasola - Google Review

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Subscriptions are based on a 12-month auto-renew basis.

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OTR Diagnostics is bluetooth based and does require you to have Wifi or Cellular coverage for you to be able to use the app.

We do have an offline mode as a feature which does require you to have internet upon first login with the adapter connected for this to function.

It is recommended to use OTR Diagnostics with internet connected to ensure properly functionality.

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OTR Diagnostics works on iOS and Android mobile phones and tablets.

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Our OTR Diagnostics hardware is backed by a Limited Lifetime Warranty, which is a testament to our commitment to your satisfaction.

Warranty Coverage: Our Limited Lifetime Warranty covers material and manufacturing defects in our OTR Diagnostics hardware for as long as you maintain an active subscription to OTR Diagnostics. We understand that your investment in our product is significant, and we want you to be confident that it will perform as designed.

For a complete understanding of our warranty terms and conditions, please refer to the terms and conditions.