Some owners of 2013 Cadillac ATS models may comment that the MIL is on. Technicians may find DTC P0171 set.
Check the engine mount vacuum control system for leaks with vacuum only. Do not use positive pressure to check the engine mount vacuum control system for leaks at the tank. Refer to Engine Mount Vacuum System Leak Test in Vacuum Operated Engine Mounts Description and Operation in the service manual.
If a leak is found at the vacuum tank, remove and replace the tank and re-check for leaks using vacuum only. If a leak is found in another component, refer to the service manual for replacement procedures. If fluid is found in the vacuum lines or tank, the entire vacuum system needs to be replaced because of contamination. If fluid is found, check for the source of the fluid.
NOTE: The engine mounts are filled with fluid.