Diesel Diagnostics

Mobile Check Engine Light & Fault Code Service

Welcome

On-Site Diagnostics for Diesel Trucks, Trailers, and Equipment

When your diesel truck’s check engine light comes on or your equipment goes into derate, fast and accurate diagnostics are critical. NoCo Diesel Services LLC offers mobile diesel diagnostics using dealer-grade scan tools and over 15 years of industry experience. Based in Johnstown, CO, we serve truckers, fleets, and equipment operators across Northern Colorado, Southern Wyoming, and Western Nebraska.


Our diagnostics service identifies the true source of fault codes and drivability issues—without unnecessary guesswork or part-swapping. We come to your location with the software, tools, and expertise needed to get your truck back on the road.

What Is a DOT Inspection?

DOT inspections are required by the Federal Motor Carrier Safety Administration (FMCSA) to ensure that commercial motor vehicles meet safety and operational standards. The most common is the annual inspection, which must be performed by a qualified inspector and documented to remain compliant with federal regulations.

Expert Mobile Diagnostics for Diesel Engines and ECM Faults

Modern diesel trucks use complex electronic systems that control everything from emissions and fuel delivery to brake function and power management. When these systems detect a fault, they log diagnostic trouble codes (DTCs), trigger warning lights, and in many cases, initiate derate or shutdown protocols. We diagnose:


  • Check engine lights
  • MIL (malfunction indicator lamp) codes
  • ECM, TCM, and ABS faults
  • Regeneration failures and soot overload
  • Fuel system errors
  • DEF and aftertreatment sensor issues
  • “No communication” errors from modules
  • Throttle, turbo, and injector performance issues
  • Starting problems and power loss
  • Air brake and ABS system codes
  • Battery, alternator, and voltage faults

When Should You Call for Diagnostics?

Many diesel problems can’t be resolved until a full scan and inspection are completed. If you're seeing any of the following symptoms, mobile diagnostics can help:

're seeing any of the following symptoms, mobile diagnostics can help:

  • Check engine or ABS light illuminated
  • Loss of power or hesitation
  • Engine cranking but not starting
  • Frequent regen failures or forced regens
  • Dash warnings such as "Service DEF System" or "Exhaust System Fault"
  • Derate or limp mode activated
  • Intermittent electrical or sensor issues
  • Sudden stalling or low idle
  • Blown fuses or no start with power

24/7 On-Site Diagnostics for Roadside and Fleet Units

If your truck won’t start, has gone into derate, or is showing engine warnings, our mobile diesel diagnostics service is available 24 hours a day. We dispatch to highways, job sites, truck yards, and terminals to perform accurate, fast diagnostic testing.

Our goal is to save you time and money by identifying the real problem on the first visit. We frequently assist with:

  • Breakdown triage
  • Emergency fault code clearing (when safe)
  • Pre-repair system testing
  • Post-repair verification scans
  • Fleet diagnostics during maintenance windows

Common Systems We Diagnose

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Engine & Fuel Systems

  • Turbo boost pressure
  • EGR valve position
  • Injector balance and timing
  • Fuel rail pressure
  • Sensor voltages and ranges
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Aftertreatment & Emissions

  • DPF soot load and regen history
  • SCR functionality
  • NOx sensor readings
  • DEF level and heater function
  • Temperature sensor mapping
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Repairs on the Same Visit

  • CAN communication faults
  • Voltage drop testing
  • Ground path integrity
  • Lighting circuit faults
  • Battery and charging health
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Brake and Chassis

  • ABS warning light diagnosis
  • Trailer brake controller errors
  • Air system pressure switches
  • Sensor timing and response
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Fleet-Friendly Services

  • Instrument cluster communication
  • HVAC actuator faults
  • Switch and signal testing

Welcome

Advanced Tools and Dealer-Level Software

NoCo Diesel Services LLC uses professional diagnostic tools that are compatible with all major manufacturers, including:


  • Cummins Insite
  • International Diamond Logic
  • Detroit Diesel Diagnostic Link (DDDL)
  • Allison DOC
  • JPRO Commercial Fleet Diagnostics
  • Bendix ACom Pro
  • OEM-compatible tools for Freightliner, Kenworth, Peterbilt, Mack, Volvo, and others

Schedule Mobile Diagnostics Now

NoCo Diesel Services LLC is ready to perform fast, accurate diagnostics anywhere you need them. If you're dealing with a check engine light, derate, or recurring system fault, call now and get expert support on-site.