OBD Operation Summary for 6.7L Diesel - MotorCraftService.com

ENGINE COOLING SYSTEM MONITORINGThermostat MonitorThe Thermostat Monitor checks that the thermostat is operating properly by modeling Engine CoolantTemperature (ECT) based on engine fueling, engine speed, vehicle speed, and the ambient temperature. Thereare increment and decrement portions to the model; the increment is based on engine speed and fuel quantity,while the decrement is derived from calculated radiator efficiency based on coolant delta temp to ambient andvehicle speed. The model is delayed by 60 seconds after engine start to negate potential errors due to block heateruse. It is also suspended while in catalyst warm-up mode due to errors in fuel quantity heat being contributed to thecoolant.Once that estimation reaches the thermostat start-to-open temperature, if the actual measured ECT has notreached a minimum warm-up temperature and the driver has not spent too much time in part fuel cut off (over30%), too low load (over 70%), too high vehicle speed (over 70%), or too low vehicle speed (over 70%) - then thethermostat is determined to be stuck open.Model at 70 deg C 1000seconds into drive cycleModel achieved 90 deg C after1600 seconds, measured coolantonly 30 deg CWarmup at -7 deg C on Unified Drive Cycle, DTC set when modeled temp reaches 90 deg C. Measured coolanttemperature was only at 30 deg C.FORD MOTOR COMPANY REVISION DATE: FEBRUARY 9, 2012 09.01.00.02-PAGE 65 OF 157