Circuit continuity check

P0117, P0118, P0119 

The circuit continuity check compares the measured engine coolant temperature with an upper and a lower threshold to detect short circuits. Additionally a check is performed to detect an intermittent contact.

If the measured engine coolant temperature signal exceeds the upper calibration limit for a calibrated period of time, a short circuit to ground is detected and a maximum fault TME will be set.

If the measured engine coolant temperature signal lies below the lower calibration limit for a calibrated period of time, a short circuit to battery or a broken wire is detected and a minimum fault TME will be set.

An intermittent contact may result in frequent jumps of the measured engine coolant temperature signal. A signal jump is detected by evaluation of the difference between the measured engine coolant temperature and the filtered engine coolant temperature. If this difference exceeds a calibrated value a "jump-detected-timer" with a calibrated time length is started and retriggered every time the difference exceeds again the calibrated value (multiple jumps).

If the overall time of the retriggered and as a result continuously running "jump-detected-timer" exceeds a calibrated period of time, an intermittent contact is detected and a plausibility fault TME is set