DOC Cleaning & Service

Professional Diesel Oxidation Catalyst cleaning to restore aftertreatment performance and prevent recurring DPF issues.

The Diesel Oxidation Catalyst (DOC) is the first stage of your truck's aftertreatment system. It sits upstream of the DPF and uses a precious-metal catalyst to oxidize carbon monoxide, hydrocarbons, and the soluble organic fraction of diesel soot. The DOC also plays a critical role during DPF regeneration by raising exhaust temperatures to the 1,100°F+ needed to burn off trapped soot. When the DOC becomes contaminated or face-plugged, the entire aftertreatment system suffers.

$200-$500

Professional Cleaning

vs.

Save 70-85%

$1,500-$3,500+

Full Replacement

Our DOC Cleaning Process

System Diagnosis

We read exhaust back-pressure, temperature differential across the DOC, and related fault codes to assess catalyst condition and confirm the DOC is the problem.

Removal & Inspection

The DOC is removed and visually inspected for face plugging, substrate damage, thermal discoloration, and contamination from coolant or oil intrusion.

Thermal & Pneumatic Cleaning

The catalyst is thermally cleaned to burn off accumulated hydrocarbon residue and soot, followed by pneumatic pulsing to clear loosened material from the substrate channels.

Flow Test & Reinstall

We verify restored airflow through the DOC with back-pressure testing before reinstallation. The system is reset and a test drive confirms proper aftertreatment function.

How the DOC Fits in Your Exhaust System

Exhaust exits the turbocharger

Hot exhaust gas flows from the engine through the turbo and into the aftertreatment system.

DOC (Diesel Oxidation Catalyst)

Oxidizes CO, HC, and NO to NO2. Raises exhaust temperature for downstream DPF regen. The catalyst must be clean and active for the entire system to function.

DPF (Diesel Particulate Filter)

Physically traps soot and particulate matter. Relies on DOC heat generation for passive and active regeneration cycles.

SCR (Selective Catalytic Reduction)

Uses DEF (urea) injection to convert remaining NOx into harmless nitrogen and water before exiting the tailpipe.

Face Plugging

The front face of the DOC substrate can become blocked by unburned fuel, oil residue, or soot from incomplete combustion. This is common with leaking fuel injectors, failed turbo seals allowing oil past, or excessive idling. Face plugging restricts exhaust flow and increases back-pressure, reducing both DOC and DPF performance.

Catalyst Contamination

The platinum and palladium catalyst coating can be poisoned by sulfur (from non-ULSD fuel), phosphorus and zinc (from incorrect engine oil), or coolant (from leaking EGR coolers or head gaskets). Contamination reduces the DOC's ability to oxidize pollutants and generate heat for regen cycles. In severe cases, the catalyst cannot be restored and replacement is necessary.

Thermal Damage

Excessive exhaust temperatures from raw fuel entering the exhaust stream (runaway regen or injector failure) can melt or sinter the catalyst substrate. We inspect for thermal discoloration and substrate integrity before cleaning. If the substrate is melted or fractured, we recommend replacement and explain why.

DOC + DPF Combined Service

Since the DOC and DPF are part of the same exhaust assembly, we inspect and service both components together. If your DPF keeps clogging despite recent cleaning, the root cause is often a degraded or plugged DOC that cannot generate sufficient heat for regeneration. Combined service addresses the whole system.

Signs Your DOC Needs Service

Check engine light with DOC-related codes (P2002, P242F, P2452)

Increased DPF regeneration frequency

Elevated exhaust back-pressure readings

Loss of power and reduced throttle response

Poor fuel economy compared to baseline

Black or dark gray exhaust smoke

Failed emissions inspection

DPF clogging repeatedly despite recent cleaning

Vehicles We Service

We clean DOCs on all major diesel platforms:

Ford Power Stroke

6.4L, 6.7L

GM Duramax

LMM, LML, L5P

Ram Cummins

6.7L (2007.5+)

Plus commercial platforms: Volvo, Freightliner, Kenworth, Peterbilt, International, Mack, and more.

DOC Cleaning FAQ

What is the difference between a DOC and a DPF?

The Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) are two separate components in the aftertreatment system. The DOC sits upstream and uses a platinum/palladium catalyst to oxidize carbon monoxide (CO), hydrocarbons (HC), and the soluble organic fraction of diesel soot. The DPF sits downstream and physically traps particulate matter. The DOC also raises exhaust temperature during regeneration events to help burn soot in the DPF. Both must function properly for the system to work.

How much does DOC cleaning cost vs. replacement?

Professional DOC cleaning typically costs $200-$500 depending on size and condition. A replacement DOC runs $1,500-$3,500+ for light-duty diesel pickups and $2,000-$5,000+ for heavy-duty commercial applications. Because the DOC contains precious metals (platinum and palladium), replacement costs are significant. Cleaning saves 70-85% compared to buying a new unit when the substrate is structurally sound.

How often does a DOC need to be cleaned?

The DOC does not accumulate ash like a DPF, so it does not require the same scheduled maintenance intervals. However, DOCs can become face-plugged or contaminated over time. We recommend inspecting the DOC whenever the DPF is pulled for cleaning. Trucks that experience frequent incomplete regeneration cycles, oil consumption issues, or coolant leaks are at higher risk for DOC contamination and should be inspected sooner.

Can a clogged DOC cause DPF problems?

Absolutely. The DOC sits directly upstream of the DPF. If the DOC is face-plugged or its catalyst is degraded, it cannot properly oxidize hydrocarbons or raise exhaust temperatures for DPF regeneration. This leads to incomplete regen cycles, accelerated soot accumulation in the DPF, and frequent DPF warning lights. If your DPF keeps clogging after cleaning, the DOC is a prime suspect.

What causes a DOC to fail?

The most common causes are face plugging from raw fuel or oil reaching the exhaust (often from leaking injectors, failed turbo seals, or excessive oil consumption), thermal damage from extremely high exhaust temperatures, coolant contamination from a cracked EGR cooler or head gasket, and catalyst poisoning from non-ULSD fuel or high-sulfur fuel. Physical damage from road debris or improper handling can also crack the substrate.

Do you clean the DOC and DPF together?

Yes. Whenever we pull a DPF for cleaning, we inspect the DOC as a standard part of the service. Since both components are part of the same aftertreatment assembly and share the same exhaust flow path, servicing both at the same time ensures optimal system performance and eliminates the need for a second visit. We offer combined pricing when both need cleaning.

Serving Willow Springs, Lemont, Burr Ridge, Hodgkins, Countryside, La Grange, Hickory Hills, Justice, Bridgeview, and the greater Chicagoland area.

DOC Problems Affecting Your Truck?

Call us today to schedule a DOC inspection. We service the DOC and DPF together to keep your entire aftertreatment system running right.

Request Appointment Call (708) 839-1515