INTRODUCTION
The ECT (Engine coolant temperature) sensor is a thermistor seen in the engine block or other coolant lead way. It varies resistance with variation in the temperature of the coolant that is in its contact. It comes as a two wire sensor. One wire is a 5 volt reference that issues from PCM (Powertrain Control Module) while the other is a ground supplied from PCM.
As the of the coolant changes temperature, the resistance of the sensor changes too. When the engine is cold, the resistance becomes high but when the engine is warm, the resistance gets low. If the PCM finds a signal voltage lower than the normal working range of the sensor then P0117 code is triggered.
SYMPTOMS
Potential symptoms include: MIL (Malfunction Indicator Lamp) illumination Poor fuel economy Poor drivability Engine may run rough or blow black smoke from the tail exhaust pipe, May not idle, May start and then die
CAUSES.
Continue reading;http://www.automobileglobe.com/how-to-troubleshoot-the-p0117-ect-circuit-malfunction/