TechShop’s ASE-certified technicians share and review a Technical Service Bulletin that applies to 2016 to 2019 Ford Fiesta vehicles with DTC P0128.
P0128 is defined by the PCM as Coolant Temperature Too Low or Faulty Coolant Thermostat. This TSB is from the Ford Motor Company and is in reference to some 2016-2019 Ford Fiesta vehicles with a 1.6L twin independent variable cam timing engine built on or before Feb. 19, 2019.
The TSB tells us that some of these cars may exhibit an illuminated MIL with DTC P0128 stored in the PCM. If you have one of these cars in your shop and P0128 is the only DTC stored, the problem may be due to some PCM software parameters related to engine temperature.