Responded to an HVAC service call in Bryn Athyn, PA 19006 for the upstairs system, a 2009 unit. Customer reported a ‘system malfunction’ error on the thermostat. On a previous visit, lint buildup from the dryer vent had been impacting the unit and required a deep outdoor system coil cleaning. Performed a diagnostic inspection today and provided recommendations to address the issue and restore reliable operation.