This article supersedes TSB 21-2011 to update the vehicle model years affected and Service Procedure. Some 2018-2022 Mustang vehicles may exhibit various concerns with the active exhaust system. These may include Drive Mode Not Available or Exhaust Mode Not Available messages, and/or illuminated malfunction indicator lamp (MIL) with diagnostics trouble codes (DTCs) P26C5, P26C6, P26FE, P2BF9, P2BFB, P26C7, P2BF5, P2BF8, P2BFD and/or P2BFA. This may be due to an improperly seated exhaust system. To correct the condition, follow the Service Procedure to diagnose the tailpipe actuator .
