What this code means

The diesel oxidation catalyst efficiency has dropped below the acceptable level. The DOC oxidizes CO and HC and raises exhaust temperature for DPF regeneration.

Symptoms

• Check Engine Light
• DPF regeneration may be affected
• Higher CO and HC emissions
• Failed emissions test
• Exhaust smell
• DPF soot loading increasing

Common causes

• DOC catalyst degradation
• Fuel sulfur contamination
• Oil consumption contaminating DOC
• Exhaust leak before DOC
• DOC temperature sensor error

Diagnostic steps

1. Compare DOC inlet and outlet temperatures during warm-up
2. Check hydrocarbon conversion efficiency
3. Inspect DOC for physical damage
4. Test exhaust temperature sensors
5. Check for exhaust leaks before DOC

Repair notes

Replace diesel oxidation catalyst. Address root cause of contamination (oil consumption, fuel quality). Check DPF system operation after DOC replacement.

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