Emissions systems keep modern trucks legal — and they drive a big share of the calls we get.
The diesel particulate filter (DPF) traps soot and has to burn it off through regeneration. The SCR system needs clean diesel exhaust fluid (DEF) and working sensors to cut NOx. When any link in that chain breaks, the engine computer responds with lamps and, eventually, a derate.
Plenty of Little Rock trucks run a duty cycle that makes this worse. Delivery routes through west Little Rock, stop-and-go on I-630, jobsite idling in Saline County, and yard moves near the port rarely give the exhaust enough steady heat to clean the filter. Summer heat adds its own problem: DEF stored hot breaks down, and poor-quality fluid sets off quality faults.
We come to the truck, read the aftertreatment codes and live data, and figure out whether the fix is a regen, a sensor, a DEF system repair, or something that needs a shop.
Our DPF, DEF & Regen Service: what the mechanic handles
- Parked (stationary) and forced regens with diagnostic software, when conditions allow
- Finding out why a truck won’t regen on its own — bad sensors, exhaust leaks, or regens that keep getting cut short
- DPF differential pressure sensor and sensor line replacement
- Exhaust gas temperature (EGT) sensor replacement
- NOx sensor diagnosis and replacement, inlet and outlet
- DEF pump, DEF heater, and dosing valve troubleshooting
- Clearing crystallized DEF from dosing valves and lines
- DEF quality problems — draining bad fluid and refilling the tank
- DEF level and quality sensor faults
- Aftertreatment fuel doser checks on engines that use one
- Exhaust leak repairs at clamps and gaskets that throw off sensor readings
- Clearing derates once the underlying problem is fixed
Jobs that belong in a shop
- DPF cleaning — an ash-loaded filter has to come off and be cleaned on a machine or replaced; a regen can’t burn ash
- DOC or SCR catalyst replacement, depending on access and parts
- Engine problems causing the soot, like injector or turbo faults, may need shop time
- Emissions deletes or tampering — illegal under federal law, and not a repair
Fix it on site or tow it?
Most aftertreatment problems can be diagnosed, and often fixed, on site. A loaded DPF that just needs a regen, a failed NOx or temperature sensor, or crystallized DEF in a dosing valve is routine mobile work.
A shop makes more sense when the DPF is full of ash and has to come off, when a regen fails because of an internal engine problem, or when the truck is too derated to reach a safe place to work. If it can still move at reduced speed, get it off the interstate to a truck stop or yard where a parked regen can run safely.
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: DPF, high exhaust system temperature, DEF, check engine, or stop engine
- Whether the DPF lamp is solid or flashing
- How derated the truck is — full power, reduced power, or crawl speed
- Any recent DEF fill, especially from a jug or unfamiliar source
- When the last regen ran and whether a parked regen was tried
- Engine make and model
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.
DPF, DEF & Regen Service across Little Rock & Central Arkansas
Regen and DEF calls come from trucks that idle and creep: delivery fleets in Little Rock and North Little Rock, dump and concrete trucks on construction sites in Saline and Faulkner counties, box trucks running store routes, and yard tractors at port warehouses. Highway trucks hit DEF derates too, often at a truck stop or on I-40 and I-30 when a sensor quits between towns.
Interstates we cover
Cities we cover
DPF, DEF & Regen Service FAQ
Can you run a forced regen on the side of the road?
Often, yes, if the truck is parked somewhere safe and the system allows it. A parked regen gets the exhaust very hot, so the truck needs to be away from dry grass, fuel spills, and anything that can burn. On a narrow shoulder, moving to a lot first is safer.
Why won’t my truck regen by itself?
Common causes are a failed differential pressure or exhaust temperature sensor, an exhaust leak, an EGR problem, or a duty cycle with so much idling and so many short trips that a regen never finishes.
What happens if I ignore a DEF warning?
Most trucks step down through harder derates, and the last stage can hold the truck to crawl speed. Fixing it early is faster and cheaper.
Does hot weather cause DEF problems?
It can. DEF stored in heat or direct sun breaks down and can trigger quality faults. Keep jugs cool and out of the sun, and don’t stockpile more than you’ll use soon.
Can a regen fix a DPF full of ash?
No. Regeneration burns soot, not ash. Ash builds up over time, and eventually the filter has to come off to be cleaned or replaced.
Will you delete my DPF or DEF system?
No. Removing or disabling emissions equipment violates federal law and causes problems with inspections, resale, and warranty. We repair these systems.