The Engine Coolant Temperature (ECT) sensor measures how warm (or cool) coolant passing through the motor is.

Ed Gibson had this to say about it: 'Temperature lookup table for OBD1 IAT Sensor from '93 CRX EDM 'Resistance mapped from sensor in lab from 0 to 100 Celcius 'ECU hex values mapped via applied equivalent resistance on car 'some degree (ahem) for error there, but I reckon on better than a couple of degrees 'Extracted from VB. Array from ECU value 255 to 0 Temperature Degrees = Array( -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, -1#, 0#, 0.5, 1#, 1.6, 2.2, 2.9, 3.5, 4.1, 4.7, 5.4, 6#, 6.5, 7#, 7.5, 8#, 8.5, 8.9, 9.4, 9.8, 10.3, 10.7, 11.1, 11.6, 12#, 12.3, 12.7, 13#, 13.5, 13.9, 14.4, 14.8, 15.3, 15.7, 16.2, 16.6, 17.1, 17.5, 17.8, 18.2, 18.5, 18.9, 19.3, 19.8, 20.2, 20.6, 21#, 21.4, 21.8, 22.3, 22.7, 23.1, 23.5, 23.9, 24.2, 24.6, 24.9, 25.3, 25.6, 26#, 26.3, 26.7, 27#, 27.4, 27.8, 28.1, 28.5, 28.9, 29.3, 29.6, 30#, 30.3, 30.7, 31#, 31.3, 31.7, 32#, 32.3, 32.7, 33#, 33.4, 33.7, 34.1, 34.4, 34.8, 35.1, 35.5, 35.9, 36.2, 36.6, 36.9, 37.3, 37.6, 38#, 38.4, 38.8, 39.1, 39.5, 39.9, 40.3, 40.6, 41#, 41.4, 41.8, 42.1, 42.5, 42.9, 43.3, 43.6, 44#, 44.4, 44.8, 45.3, 45.7, 46.1, 46.5, 46.9, 47.3, 47.8, 48.2, 48.6, 49#, 49.5, 50.1, 50.6, 51.2, 51.7, 52.3, 52.8, 53.4, 53.9, 54.5, 55#, 55.5, 56#, 56.5, 57#, 57.5, 58#, 58.5, 59#, 59.5, 60#, 60.5, 61#, 61.7, 62.4, 63.1, 63.8, 64.5, 65.2, 65.9, 66.6, 67.3, 68#, 68.7, 69.4, 70.1, 70.8, 71.5, 72.2, 72.9, 73.6, 74.3, 75#, 75.8, 76.6, 77.5, 78.3, 79.1, 79.9, 80.7, 81.5, 82.4, 83.2, 84#, 85.2, 86.4, 87.7, 88.9, 90.1, 91.3, 92.6, 93.8, 95#, 96.7, 98.3, 100#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#, 101#)