Abstract: A child seat adapted for use in a vehicle, the child seat comprising: a shell portion; a harness for securing a child to the child seat, the harness comprising adjustable harness tether(s) secured to the shell portion at one end and having a latch plate at the other, the latch plate being configured to releasably engage a buckle of the harness; a tension sensor(s) for providing a signal indicative of a tension of the adjustable harness tether(s); and an electronic control unit secured to the shell portion, the electronic control unit being operably coupled to the tension sensor(s) to receive the signal, the electronic control unit being capable of processing the signal to compare the signal to a signal indicative of a predetermined range of acceptable tension, wherein the electronic control unit provides an output indicating whether the tension of the adjustable harness tether(s) is(are) within the predetermined range.