OBD Operation Summary for Fiesta - MotorCraftService.com

Cold Start Emission Reduction System MonitorThe Cold Start Emission Reduction System Monitor was introduced for the 2007 MY on vehicles that meet the LEV-IIemission standards. It replaces the Cold Start Emission Reduction Component Monitor. The Cold Start EmissionReduction (CSER) Monitor detects the lack of catalyst warm up resulting from a failure to apply sufficient CSER during acold start. It does this by using the inferred catalyst temperature model to determine how closely the actual catalysttemperature follows the expected catalyst temperature during a cold start. How closely the actual temperature followsthe expected temperature is reflected in a ratio which is compared with a calibratable threshold.Temperatures UsedThe actual catalyst temperature is the same inferred catalyst temperature that is used by other portions of the enginecontrol system, including the CSER control system. The inputs to this actual temperature are measured engine speed,measured air mass, and commanded spark.The expected catalyst temperature is calculated using the same algorithm as the actual catalyst temperature, but theinputs are different. Desired engine speed replaces measured engine speed, desired air mass replaces measured airmass, and desired cold start spark replaces commanded spark. The resulting temperature represents the catalysttemperature that is expected if CSER is functioning properly.Ratio CalculationA ratio is calculated to reflect how closely the actual temperature has followed the expected temperature. This ratio isthe difference between the two temperatures at a certain time-since-start divided by the increase in expectedtemperature over the same time period. The ratio, then, provides a measure of how much loss of catalyst heatingoccurred over that time period.This ratio correlates to tailpipe emissions. Therefore applying a threshold to it allows illumination of the MIL at theappropriate emissions level. The threshold is a function of ECT at engine start.General CSER Monitor OperationDuring the first 15 seconds of a cold start, the monitor checks the entry conditions, counts time in idle, and observescatalyst temperature.If the expected change in catalyst temperature is large enough, the monitor calculates the ratio as described above.Otherwise the monitor does not make a call.The monitor then begins the waiting period, which lasts from the time the ratio is calculated (15 seconds after enginestart) until 300 seconds after engine start. This 5-minute wait allows time to diagnose other components and systemsthat affect the validity of the catalyst temperature model. During this waiting period, there are no constraints on drivecycle and the monitor cannot be disabled without turning off the key.At the end of the waiting period, if no other faults that could compromise the validity the catalyst temperature model arefound, the monitor compares the ratio to the threshold.If the ratio exceeds the threshold, the monitor considers the test a fail, and the monitor is complete.If the ratio falls below the threshold, the monitor determines whether the idle time was sufficient. If so, it considers thetest a pass and the monitor is complete. If idle time was not sufficient, the monitor does not make a call and does notcomplete. This prevents tip-ins from resulting in false passes.CONTINENTAL REVISED: SEPTEMBER 17, 2010 PAGE 65 OF 111