Rationality checks

Low side check 

P112B, 

The low side check calculates a reference engine coolant temperature with help of a temperature model. This calculated temperature is reduced by a calibrated safety margin and compared with the actual measured engine coolant temperature.

If the measured engine coolant temperature lies below the calculated and reduced temperature for a calibrated period of time, a minimum fault TMP will be set.

Stuck check 

P0116, 

The stuck check monitors the rise and drop behavior of the coolant temperature during a change in engine operation conditions.

If the engine coolant temperature change (difference of maximum and minimum occurred value) lies below a calibrated limit for a calibrated number of driving condition changes (rise and drop), a plausibility fault TMP will be set.

If a blockheater is detected, the temperature model calculations are retriggered and the rationality checks are disabled for a calibrated period of time. This is done to avoid false diagnosis.