DPF / GPF sensing — soot, ash, differential pressure and EGT
DPF fault says ‘filter overloaded’. Before condemning the filter, prove whether the pressure and temperature sensors are telling the truth.
What this lesson covers
CORE TEACHING DPF vs GPF/OPF basics; soot vs ash; differential-pressure sensor and hoses; expected pressure trend rather than one universal number; exhaust gas temperature sensors; calculated soot load; distance since regen; pressure plausibility KOEO; cracked/blocked hoses; sensor offset. PRACTICAL DEMONSTRATIONS AND TESTS Check differential pressure KOEO; inspect hoses; graph pressure at idle and raised RPM under safe conditions; compare soot/ash/load PIDs; graph EGT sensors during warm-up; apply controlled pressure to sensor if suitable equipment/spec is available. ADVANCED / SCAN TOOL LAYER Scan DPF load, differential pressure, EGT 1/2/3; graph pressure vs RPM; scope/intermittent sensor signals if required. KEY DIAGNOSTIC QUESTIONS Is pressure near plausible baseline with engine off? Does it rise smoothly with exhaust flow? Are hoses clear? Do EGT sensors agree when cold? MUST-COVER CHECKPOINTS Sensor plausibility; pressure hoses; pressure vs RPM; soot vs ash; EGTs; regen prerequisites; root cause; post-repair verification.
What you will be able to do
DPF fault says ‘filter overloaded’. Before condemning the filter, prove whether the pressure and temperature sensors are telling the truth.
Where it sits in the programme
- Builds on
- Lesson 42: EGR systems — electrical command vs actual gas flow
- Feeds into
- Lesson 44: DPF regeneration diagnosis — why a regen will not complete