GMC T-Series 2007 Owner's Manual page 91

7. If the vehicle has Power Take Off (PTO), turn
the PTO off. See Power Take-Off (PTO) on
page 79.
8. Press the DPF switch on the instrument
panel. See Instrument Panel Overview on
page 100. The green DPF indicator light
comes on, the exhaust gas control valve
operates, engine idle speed automatically
increases, and DPF regeneration begins.
Do not leave the vehicle unattended during
manual regeneration.
9. When the green DPF indicator light goes off,
regeneration is completed. Regeneration is
normally completed in about 30 minutes.
Under certain operating conditions, manual
regeneration might not be able to be performed,
even if the soot level in the DPF requires
regeneration. This can occur because of low
coolant temperature, low battery voltage, or
high exhaust temperature or immediately after
starting the vehicle. When manual regeneration is
requested, by pressing the DPF switch, when
coolant temperature is low, the exhaust restrictor
is engaged, the exhaust brake light comes on,
and engine rpm increases to help raise engine
coolant temperature. When operating conditions
allow, the green DPF indicator will come on
to indicate that regeneration has started.
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