DPF / SCR System Diagnostics
Emissions systems cause many derates on modern diesels. Diagnostics help identify whether the fault is a sensor, a blocked component, DEF-related or something upstream.
- AvailabilityCalls and messages 24/7
- WhereRoadside, yard or jobsite
- CategoryHeavy-Duty Truck Repair
- On-site repairWhere feasible and safe
About dpf / scr system diagnostics.
Emissions systems cause many derates on modern diesels. Diagnostics help identify whether the fault is a sensor, a blocked component, DEF-related or something upstream.
A mobile mechanic can look at the unit where it stands, whether that is the roadside, a yard or a jobsite. That can avoid a tow and shorten downtime when the fault is suited to on-site work.
Part of Heavy-Duty Truck Repair.
When you might need it.
Any of these is a good reason to call and describe what the unit is doing.
Emissions warning lights or derate
DEF quality or level warnings
Frequent regeneration
Reduced power
What the service involves.
Reading emissions-related fault codes
Checking sensors, wiring and DEF supply
Assessing regeneration conditions
Recommending the appropriate repair
Causes and good habits.
These are possibilities, not a diagnosis. The only way to know is to test the unit.
Possible causes
- Sensor or wiring faults
- Blocked or saturated filters
- DEF quality, level or dosing problems
Practical tips
- Use DEF that meets specification
- Do not ignore early emissions warnings
What to expect.
Some emissions repairs need specific parts or equipment. We do not advise removing or defeating emissions equipment.
On-site repair depends on the fault, parts, vehicle condition, safety and service feasibility.
(437) 601-8551Before you call
- Exact location, and direction of travel on a highway
- Truck or trailer type, make and year if known
- What happened and what warnings you see
- Whether the unit is somewhere safe
- A number we can call back
From the first call to the fix.
Call or message
Tell us where the unit is.
Describe the fault
Symptoms, lights, noises, leaks.
Agree the plan
Feasibility and dispatch, discussed honestly.
Diagnose and repair
On site where it is possible and safe.
Services that often go together.
Check Engine Light Diagnostics
A warning light is a symptom, not a diagnosis.
Sensor Replacement
Modern trucks rely on sensors to manage the engine, emissions and braking.
Engine Diagnostics & Troubleshooting
When a heavy-duty engine derates, stalls, loses power or throws fault codes, finding the actual cause matters more than clearing a light.
Fuel System Repair
Fuel faults show up as stalling, hard starting or weak power.
Frequently asked questions.
Can you fix a derate?
Diagnosis comes first. Some causes are quick to resolve, others are not.
How do I request this service?
Call (437) 601-8551 or message us on WhatsApp with your location and the issue. For non-urgent work, use the contact form.
Can every repair be done on site?
No. It depends on the fault, parts, vehicle condition, safety and feasibility.
Stranded on the Road? Let's Talk.
Tell us where your truck or trailer is located and what happened. Contact Fellows to discuss mobile repair options and next steps.
(437) 601-8551Have ready: exact location, truck or trailer type, what happened or what warnings you see, whether the unit is somewhere safe, and a callback number. Timing, dispatch and on-site repair depend on location, availability, the fault, parts and safety.