DOC Cleaning

The DOC is the first component in a diesel truck's aftertreatment system. It oxidises carbon monoxide (CO), hydrocarbons (HC), and some particulate matter in the exhaust stream before it reaches the DPF. Over time, the catalyst substrate becomes coated with oil ash, hydrocarbon deposits, and contaminants that reduce oxidation efficiency. When the DOC underperforms, the DPF receives more soot load than designed, leading to more frequent regenerations, increased DPF clogging, and higher emission readings.

Common symptoms include: increased regeneration frequency (DPF regenerating more often than usual), active regeneration failures or incomplete regenerations, elevated exhaust emission readings (CO/HC), DPF warning lights, fuel injected into the exhaust for regen not igniting properly, and in severe cases, DEF consumption increasing abnormally.

In most cases, a DOC that has been contaminated by oil ash or hydrocarbon deposits can be successfully cleaned and restored to near-OEM efficiency. Replacement is only necessary if the substrate has suffered physical damage (cracking, melting from thermal runaway) or if catalyst poisoning from incompatible additives has permanently degraded the precious metal coating. Our pre-cleaning inspection will determine which applies to your unit.

A clean, fully efficient DOC significantly reduces the soot loading rate on the DPF downstream. This means longer intervals between DPF cleaning, fewer forced regeneration events, and ultimately a longer DPF service life. Customers who clean their DOC regularly often see DPF cleaning intervals extended by 20–40%.

DOC cleaning typically takes 8–24 hours from drop-off to reinstallation, depending on contamination level and the truck model. Our technician will give you an accurate timeframe after the initial inspection.

Yes - our cleaning process is specifically designed to remove surface contamination without harming the precious metal (platinum, palladium, rhodium) wash coat on the substrate. We do not use aggressive chemicals or thermal processes that could strip the catalyst coating. Efficiency is tested before and after to verify the substrate remains intact.

Yes, and we recommend it. When your DPF needs cleaning, the DOC should be inspected and cleaned at the same time. A contaminated DOC will cause a freshly cleaned DPF to clog more quickly. We offer a combined DOC + DPF cleaning package - ask about it when you book.