Check Engine Light With EGR Codes
EGR codes point at the valve, the cooler or the flow through them. The codes and the readings get pulled before any part gets replaced.
Checked:EGR valveEGR coolerSensors
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Heavy-duty EGR & DPF · Louisville, KYEGR & DPF RepairFor Heavy-Duty Trucks.
The EGR system cuts the NOx your diesel makes, and the DPF catches the soot before it leaves the stack. When either one acts up, the truck loses power, sets codes or goes into a derate. Superior Truck & Trailer diagnoses and repairs both on heavy-duty trucks and fleets in Louisville, KY.
- The EGR SystemValve, cooler and the loop
- The DPFSoot and regeneration
- Faults & CleaningSensors, ash and causes
Two systems, one exhaust
EGR And DPF.
A diesel with its EGR loop and its particulate filter: exhaust going back to the intake through the cooler, and soot stopping in the filter on the way out.
The EGR System
The EGR system sends some of the exhaust through a cooler and back into the air intake. That cooler exhaust lowers the combustion temperature, and a cooler burn makes less NOx. The hotter the engine runs, the more NOx it makes.
The Diesel Particulate Filter
All of the exhaust flows through the DPF, and a fine mesh-like material catches the soot and carbon before it leaves the truck. The filter only holds so much, so it has to be regenerated. Some DPFs regenerate on their own, others have to be regenerated manually.
DPF Faults And Cleaning
A regen burns off soot but leaves ash behind, so a DPF eventually needs cleaning. Its sensors decide when it regenerates, and a lot of DPF trouble starts upstream at the EGR or the engine. All three get looked at before a filter gets replaced.
EGR checklist
EGR flow: what gets checked
- EGR codes and freeze-frame data
- EGR flow against what is commanded
- Intake and exhaust temperatures
- Boost and intake pressure
- Carbon in the intake and mixer
- Leaks in the EGR pipes
The EGR valve: what gets checked
- Carbon build-up on the valve
- A valve sticking open or shut
- The actuator and its wiring
- Valve position readings
- Commanded against actual opening
- Gaskets at the valve
The EGR cooler: what gets checked
- Coolant loss with no puddle
- White smoke or steam at the stack
- Pressure test of the cooler
- A plugged cooler cutting flow
- Exhaust temperature out of the cooler
- Coolant hoses and connections
DPF checklist
Soot load: what gets checked
- Pressure across the filter
- Soot load on the scan tool
- DPF lamp and codes
- Why the engine is making soot
- Leaks ahead of the filter
- Miles and hours on the filter
Automatic regen: what gets checked
- Regen history and how often
- Regens that start and stop
- Exhaust temperatures during a regen
- The DOC ahead of the filter
- Idle time and short runs
- Anything blocking a regen
Manual regen: what gets checked
- Whether a parked regen is due
- Codes that must be fixed first
- Temperatures through the regen
- Soot load before and after
- Why automatic regens are not finishing
- Whether cleaning is the better fix
Faults and cleaning checklist
Cleaning: what gets checked
- Pressure after a full regen
- Ash load and filter age
- Cleaning or a replacement
- Cracked or melted substrate
- The face of the DOC
- Gaskets and clamps on reinstall
Sensors: what gets checked
- Differential pressure sensor
- Its lines and connections
- Exhaust temperature sensors
- Readings that disagree
- Wiring and connectors
- Codes and freeze-frame data
Upstream causes: what gets checked
- An EGR valve stuck open
- A leaking EGR cooler
- Injectors and fueling
- Turbo oil getting into the exhaust
- Boost leaks and air filter
- Oil or coolant in the filter
EGR and DPF, part by part
EGR ValveCarbon, sticking and the actuator, diagnosed and repaired.
EGR CoolerLeaks, plugging and coolant loss into the exhaust.
EGR Pipes & MixerCarbon build-up and leaks in the loop.
Diesel Particulate FilterSoot load, regeneration and damage.
RegenerationAutomatic regens that fail, and manual regens.
DPF & EGR SensorsPressure, temperature and position sensors and wiring.
Related repairs and services
Exhaust System RepairLeaks, the DPF at a glance and the SCR catalyst.Engine Repair, Rebuild & ConversionWhen the soot or the oil starts at the engine.Coolant System RepairCoolant loss, hoses and the cooling system.Diagnostics & Electrical RepairSensor codes, wiring and the scan tool.General Diesel RepairDiesel repair across the whole truck.24/7 Mobile & Roadside AssistanceA derate on the interstate, any hour.
What drivers notice first
Signs Of An EGR Or DPF Problem.
Where each one usually leads. Caught early, a sticking EGR valve is a cleaning or a valve, not a filter and a tow.
Black Smoke And Low Power
An EGR valve stuck open lets too much exhaust into the intake. The engine loses power, smokes and sends extra soot to the DPF.
Checked:EGR valveIntakeDPF
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Losing Coolant With No Puddle
Coolant that keeps going down with nothing on the ground can be a leaking EGR cooler sending coolant into the exhaust, often with white smoke at the stack.
Checked:EGR coolerPressure testDPF
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DPF Light Or Regens More Often
A DPF lamp, or regens coming closer and closer together, mean the filter is loading faster than it burns clean or is full of ash.
Checked:Soot loadRegen historyAsh
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Loss Of Power Or A Derate
A plugged DPF or an EGR fault can put the truck into a derate, with the speed held down until the problem gets fixed.
Checked:DPFEGRSensors
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Rough Idle Or Stalling
An EGR valve that sticks open at idle feeds exhaust into the intake when the engine needs clean air, and the idle goes rough or the engine stalls.
Checked:EGR valveActuatorIntake
Often a repair
EGR and DPF work
From The Intake To The Filter.
EGR and DPF work runs from the intake side of the engine to the filter in the exhaust, and the two are often connected.
How EGR and DPF work moves through the shop
From the first call to a clean-running truck.
Tell us the truck and what it is doing. We pull the codes and check the EGR and the DPF, lay out the repair, do the work and get the truck back into service.
01You call
Tell us the truck, the codes on the dash and what it is doing: the lamp, the smoke, the derate.
02We check it
The codes and readings get pulled, and the EGR and the DPF get checked together.
03You approve it
The valve, the cooler, the regen or the cleaning, laid out up front. Nothing gets done until you approve it.
04You roll
The repair gets done, the codes get cleared and checked, and the truck goes back to work.
Working trucks, real shop work
The work happens here, on the road and in the bay.
The trucks, trailers, service vehicles, roadside calls and shop work behind the services on this site. This is the kind of commercial equipment Superior works on every day in and around Louisville.
Truck repair customer reviews
What Drivers SayAbout The Shop.
Read customer feedback on Superior Truck & Trailer's repair work, communication, and service experience in Louisville.
EGR and DPF work backed by a full truck shop
The Rest Of The Truck,Same Shop.
EGR and DPF problems often start somewhere else on the truck. Everything else it needs is handled from the same Louisville shop.
EGR and DPF FAQ · Louisville, KY
EGR And DPF Questions.
EGR valves, EGR coolers, regens and cleaning: the EGR and DPF questions truck owners and fleets ask most.
(502) 789-6644What does the EGR system do on a diesel truck?
The exhaust gas recirculation (EGR) system limits the nitrogen oxides (NOx) a heavy-duty diesel produces. It sends some of the exhaust through a cooler and back into the air intake. That cooler exhaust lowers the combustion temperature, and a cooler burn makes less NOx.
Why does engine temperature matter for NOx?
NOx output depends heavily on how hot the engine burns. The hotter the combustion, the more NOx gets produced, which is why the EGR system works by lowering the combustion temperature.
What does the EGR cooler do?
It cools the exhaust before it goes back into the intake, using the engine coolant. A leaking cooler can let coolant into the exhaust, and a plugged cooler cuts the EGR flow.
What are the signs of a bad EGR valve?
Common signs are a check engine light with EGR codes, loss of power, black smoke, a rough idle or stalling, and more soot going to the DPF. A valve stuck open or shut, or one caked with carbon, is a common cause.
Can a bad EGR cooler cause coolant loss?
Yes. A leaking EGR cooler can send coolant into the exhaust, so the coolant level keeps dropping with no puddle under the truck, often with white smoke or steam at the stack.
What does a diesel particulate filter do?
The DPF captures soot and carbon before they leave the exhaust. It is built into the exhaust, so all of the exhaust gas flows through it, and a fine mesh-like material catches the soot.
What is DPF regeneration?
A DPF only holds so much soot, so it has to be regenerated: the exhaust gets hot enough to burn the trapped soot off. Some DPFs regenerate automatically, while others have to be regenerated manually.
What is the difference between an automatic and a manual regen?
An automatic regen happens on its own while the truck is working. A manual regen is started on purpose, usually with the truck parked, when the filter needs one and an automatic regen has not finished the job.
Why does my DPF keep clogging?
A filter that keeps filling up fast usually has a cause upstream: an EGR valve stuck open, a leaking EGR cooler, fueling or injector problems, or oil getting into the exhaust. Lots of idling and short runs that never let a regen finish also add up.
Does a DPF need cleaning?
Yes, eventually. A regen burns off soot but leaves ash behind, and ash builds up over the life of the filter. When the pressure across the filter stays high even after a full regen, it needs cleaning or replacement.
Can an EGR or DPF problem cause a derate?
Yes. A plugged DPF, an EGR fault or a bad sensor reading can put the truck into a derate, with the speed held down until the fault gets fixed. The fault gets diagnosed with the codes and the readings before any part is replaced.
Where can I get EGR and DPF repair near Louisville, KY?
Superior Truck & Trailer repairs EGR systems and diesel particulate filters on heavy-duty trucks at 3816 Bishop Lane in Louisville, KY, for trucks from Louisville and the surrounding Kentucky and Southern Indiana counties. Call (502) 789-6644 with the truck, the codes and what it is doing.
EGR codes, a DPF lamp or a derate?
Get The EGR And DPF Sorted.
Call Superior Truck & Trailer in Louisville, KY with the truck, any codes and what it is doing. We'll find the fault, fix what caused it and get it running clean.
(502) 789-6644
3816 Bishop Lane #1, Louisville, KY 40218