Most technicians know that a defective engine coolant temperature sensor (ECT) can harm driveability, but what else can this sensor affect and what other problems can it cause? And while we’re at it, how does a PCM monitor the output from the coolant temperature sensor? Stay tuned while we discuss how engine temperature sensors work and what they influence. Last of all, we’ll examine some unusual coolant temperature sensor monitoring methods employed by PCMs from different manufacturers.