Knocking under hood - '07 Envoy

artiefartief Member Posts: 1
edited December 2014 in GMC
My stabilitrak light came on but is now off, however there is now a knocking and it sounds as if it is under the dash ---but---when I turn the heater on the knocking goes away-heater off-there is knocking--heater on-no knocking. Help?
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