Last month, we began a new series on analog electronic sensorship by discussing the throttle position sensor. This month, we’re going to spend some time with coolant temperature sensors. If you were to rank all of the PCM’s input sensors, the coolant temperature sensor would have to place very near the top of the list. Many of the PCM’s strategies for controlling the engine to maintain optimum fuel economy and minimum emissions are based in part of the information the coolant temperature sensor circuit provides to the PCM.