The Periodic Heat Mode (PHM) is used to burn off hydrocarbons and ventilate vapours that have collected in the aftertreatment diesel particulate filter (DPF) after extended idle periods. If the PHM process does not function, the aftertreatment diesel particulate filter (DPF) may crack when regeneration begins because of the accumulated hydrocarbons.

Conditions for diagnostic trouble code (DTC):
1) Vehicle idle time without Periodic Heat Mode is critically too long

Observable symptoms
1) White/gray smoke
2) High temperature spikes in the aftertreatment diesel particulate filter (DPF), when resuming driving or stationary aftertreatment DPF regenerations
3) Low Power

Probable cause
1) Extended idling in extremely cold ambient air temperature conditions
2) Idling with PTO engaged, PHM is inhibited in PTO mode
3) Engine Turbo Compressor Bypass Valve
4) Variable Geometry Turbo

Detailed information
1) Activation
2) Engine de-rated