On a modern diesel, the fault code is where diagnosis begins, not where it ends.
When something goes wrong, the engine control module logs a fault and — depending on how serious it is — lights the dash, cuts power, or shuts the engine down. A NOx sensor code might mean a bad sensor, a wiring problem, poor-quality DEF, or an exhaust leak upstream. Replacing parts based on the code alone is how trucks end up with three new sensors and the same lamp.
Mobile diagnostics means a mechanic comes to your truck with a scan tool and software, reads active and inactive codes, watches live sensor data, and tests the parts involved. The goal is fixing the real problem the first time.
For a driver sitting at the Galloway truck stops or on the I-30 shoulder, the most important answer is usually the simplest: can this truck make the delivery, or does it need fixing right here?
Our Diesel Engine Diagnostics: what the mechanic handles
- Reading active and inactive codes on engine, transmission, ABS, and aftertreatment modules
- Reviewing live data — boost, fuel pressure, coolant and oil temperature, exhaust temperatures, and DPF differential pressure
- Derate and limp-mode troubleshooting
- Testing and replacing sensors: NOx, exhaust temperature, DPF differential pressure, coolant temperature, oil pressure, and crank and cam position
- Wiring and connector checks for chafed harnesses and corroded pins
- Boost leak, charge air cooler, and cracked intake pipe checks
- EGR valve and EGR-related faults
- Turbocharger actuator faults
- Parked regens and other service routines when the software and system allow
- Clearing codes after a repair and confirming the fault stays gone
- A plain-English write-up so a fleet manager or shop knows exactly what was found
Jobs that belong in a shop
Diagnostics can pinpoint nearly anything, but not every problem it finds is an on-site fix:
- Internal engine damage — low compression, a failed injector cup, or coolant in the oil — usually means shop work
- Some module programming and parameter changes need OEM dealer access
- Warranty failures may need to go to an authorized dealer to keep coverage
- Jobs needing major teardown, like EGR cooler replacement on some engines, are often better done indoors
Even when the repair happens elsewhere, a clear diagnosis saves money: the truck goes to the right shop, for the right job, with parts ordered ahead.
Fix it on site or tow it?
A code doesn’t automatically mean a tow. Many faults come down to sensors, wiring, or connectors that can be repaired where the truck sits. Some let you drive at reduced power to a safe spot or a shop. Others — low oil pressure, high coolant temperature, or anything that shuts the engine down — mean the truck stays put until the cause is found.
A red stop-engine lamp means exactly that: get off the road safely and shut it down. An amber warning gives you more room, but keep an eye on it, especially in summer heat, and call before it escalates.
What to tell dispatch
Give us these details on the first call so the mechanic shows up with the right parts and finishes in one trip.
- Which lamps are on (check engine, stop engine, DPF, DEF, high exhaust temperature) and any dash message
- Fault codes, if your dash shows them
- Whether the truck is derated, and how much power it has
- Engine make and model — Cummins X15, Detroit DD15, PACCAR MX-13, Volvo D13, and so on
- What the truck was doing when the lamp came on — climbing, idling, just after fueling
Trucks & engines we service
- Freightliner
- Peterbilt
- Kenworth
- Volvo
- Mack
- International
- Western Star
Class 6 through Class 8 trucks, with engines from Cummins, Detroit Diesel, PACCAR, Volvo, Mack, Navistar, and Caterpillar.
Diesel Engine Diagnostics across Little Rock & Central Arkansas
Diagnostic calls come from fleet yards across Pulaski and Saline counties, the truck stops at Galloway and along I-30, and interstate shoulders where a derate forced a driver over — often on I-40 between Conway and North Little Rock or on I-30 heading into Benton.
Interstates we cover
Cities we cover
Diesel Engine Diagnostics FAQ
Can you tell me if my truck is safe to drive?
That’s usually the first thing we answer. Some faults let the truck run normally or at reduced power; others mean the engine should stay off until it’s repaired.
Can’t I just clear the code and go?
Clearing a code doesn’t fix the cause, and many emissions faults come right back or step up to a harder derate. Some won’t clear at all until the problem is repaired.
What is a derate?
The engine computer has limited power or road speed, either to protect the engine or to force an emissions repair. Derates often get worse in stages if nothing is fixed.
Do you have software for my engine?
Give dispatch your engine make and model when you call so the mechanic comes prepared for your truck.
Can you track down a problem that comes and goes?
Intermittent faults are harder, but inactive codes and freeze-frame data often show what was happening when the fault set. Describe exactly when it happens — under load, in the heat, after fueling.
Can you check transmission and ABS lamps too?
Yes. Transmission and ABS modules store codes too, and we read them along with the engine.