2088094XS | Genuine Paccar® DOC Module, Inlet Catalyst

1. Reduce Harmful Emissions

Oxidizes (chemically reacts with) pollutants in the exhaust:
Carbon Monoxide (CO) → Carbon Dioxide (CO₂)
Unburned Hydrocarbons (HC) → Water (H₂O) + CO₂
Soluble organic fraction (SOF) of soot → burned off

2. Increase Exhaust Temperature

The oxidation reaction inside the DOC heats the exhaust.
This increased temperature helps ignite and burn soot in the DPF, supporting regeneration.

3. Prepare Exhaust for Next Stage

Acts as a pre-treatment stage before gases reach the:
DPF (which traps soot)
SCR (Selective Catalytic Reduction, which reduces NOx)

4. Help Meet Emission Regulations

Without the DOC, a diesel engine would emit illegal levels of CO and HC.
It's required to comply with EPA, CARB, Euro VI, and similar emissions standards.

1. Check Engine Light (CEL) or Emissions Warning

Triggered by fault codes such as:
DOC efficiency below threshold
Exhaust temp too low
High soot load in DPF
Codes: P0420, P244A, SPN 3251, SPN 3242 (varies by make/ECM)

2. Poor DPF Regeneration

DOC failure = insufficient heat → DPF cannot regenerate properly.
Signs:
Frequent regens
Incomplete regens
DPF clogging
DPF-related derate

3. Excessive Soot or Smoke

If the DOC isn’t oxidizing hydrocarbons and soluble organics, you may notice:
Visible black smoke
Oily soot in exhaust stack

4. Low Exhaust Temperatures

The DOC is responsible for increasing exhaust temp before the DPF.
If it's damaged, temp sensors downstream will show consistently low temps, causing:
Delayed or failed regen cycles
Poor SCR performance

5. Engine Derate or Power Loss

Emissions system faults can trigger automatic power reduction to protect the engine and maintain compliance.
Some trucks go into derate mode if DOC efficiency drops too low.

6. Fuel Efficiency Drop

Faulty DOC can disrupt aftertreatment cycles, causing:
More frequent regens
Higher fuel consumption