Diagnostic Overview
Mack fault code P269900 commonly relates to aftertreatment fuel dosing or hydrocarbon dosing performance. This system helps raise exhaust temperature for DPF regeneration. If it fails, the DPF may not regenerate correctly and soot loading may increase. The code should be checked alongside DPF differential pressure and exhaust temperature data.
Likely Causes
Failed aftertreatment fuel injector/doser; plugged doser; restricted fuel supply; wiring issue; failed control valve; exhaust temperature sensor issue.
What To Check First
Inspect and test the aftertreatment fuel doser, verify fuel supply, check wiring and connectors, and confirm that commanded dosing causes the expected temperature rise.