Cars · Diagnostics
Engine Coolant Temperature Sensor Reference
Technical reference for the Engine Coolant Temperature (ECT) sensor, including ECU lookup tables and operational characteristics for OBD1 Honda systems.
The Engine Coolant Temperature (ECT) sensor is a thermistor that measures the temperature of the engine coolant. The ECU uses this data to adjust fuel enrichment, ignition timing, and idle speed based on engine thermal state.
Important
The following data represents the temperature lookup table for the OBD1 ECT sensor, derived from a 1993 CRX (EDM). Values are mapped from ECU hex data (255 to 0) to degrees Celsius.
ECT Lookup Table
The table below correlates the raw ECU hex value (255â0) to the corresponding temperature in degrees Celsius.
| ECU Hex Value | Temp (°C) | ECU Hex Value | Temp (°C) | ECU Hex Value | Temp (°C) |
|---|---|---|---|---|---|
| 255â211 | -1 | 140 | 23.5 | 69 | 48.6 |
| 210 | 0 | 139 | 23.9 | 68 | 49.0 |
| 209 | 0.5 | 138 | 24.2 | 67 | 49.5 |
| 208 | 1.0 | 137 | 24.6 | 66 | 50.1 |
| 207 | 1.6 | 136 | 24.9 | 65 | 50.6 |
| 206 | 2.2 | 135 | 25.3 | 64 | 51.2 |
| 205 | 2.9 | 134 | 25.6 | 63 | 51.7 |
| 204 | 3.5 | 133 | 26.0 | 62 | 52.3 |
| 203 | 4.1 | 132 | 26.3 | 61 | 52.8 |
| 202 | 4.7 | 131 | 26.7 | 60 | 53.4 |
| 201 | 5.4 | 130 | 27.0 | 59 | 53.9 |
| 200 | 6.0 | 129 | 27.4 | 58 | 54.5 |
| 199 | 6.5 | 128 | 27.8 | 57 | 55.0 |
| 198 | 7.0 | 127 | 28.1 | 56 | 55.5 |
| 197 | 7.5 | 126 | 28.5 | 55 | 56.0 |
| 196 | 8.0 | 125 | 28.9 | 54 | 56.5 |
| 195 | 8.5 | 124 | 29.3 | 53 | 57.0 |
| 194 | 8.9 | 123 | 29.6 | 52 | 57.5 |
| 193 | 9.4 | 122 | 30.0 | 51 | 58.0 |
| 192 | 9.8 | 121 | 30.3 | 50 | 58.5 |
| 191 | 10.3 | 120 | 30.7 | 49 | 59.0 |
| 190 | 10.7 | 119 | 31.0 | 48 | 59.5 |
| 189 | 11.1 | 118 | 31.3 | 47 | 60.0 |
| 188 | 11.6 | 117 | 31.7 | 46 | 60.5 |
| 187 | 12.0 | 116 | 32.0 | 45 | 61.0 |
| 186 | 12.3 | 115 | 32.3 | 44 | 61.7 |
| 185 | 12.7 | 114 | 32.7 | 43 | 62.4 |
| 184 | 13.0 | 113 | 33.0 | 42 | 63.1 |
| 183 | 13.5 | 112 | 33.4 | 41 | 63.8 |
| 182 | 13.9 | 111 | 33.7 | 40 | 64.5 |
| 181 | 14.4 | 110 | 34.1 | 39 | 65.2 |
| 180 | 14.8 | 109 | 34.4 | 38 | 65.9 |
| 179 | 15.3 | 108 | 34.8 | 37 | 66.6 |
| 178 | 15.7 | 107 | 35.1 | 36 | 67.3 |
| 177 | 16.2 | 106 | 35.5 | 35 | 68.0 |
| 176 | 16.6 | 105 | 35.9 | 34 | 68.7 |
| 175 | 17.1 | 104 | 36.2 | 33 | 69.4 |
| 174 | 17.5 | 103 | 36.6 | 32 | 70.1 |
| 173 | 17.8 | 102 | 36.9 | 31 | 70.8 |
| 172 | 18.2 | 101 | 37.3 | 30 | 71.5 |
| 171 | 18.5 | 100 | 37.6 | 29 | 72.2 |
| 170 | 18.9 | 99 | 38.0 | 28 | 72.9 |
| 169 | 19.3 | 98 | 38.4 | 27 | 73.6 |
| 168 | 19.8 | 97 | 38.8 | 26 | 74.3 |
| 167 | 20.2 | 96 | 39.1 | 25 | 75.0 |
| 166 | 20.6 | 95 | 39.5 | 24 | 75.8 |
| 165 | 21.0 | 94 | 39.9 | 23 | 76.6 |
| 164 | 21.4 | 93 | 40.3 | 22 | 77.5 |
| 163 | 21.8 | 92 | 40.6 | 21 | 78.3 |
| 162 | 22.3 | 91 | 41.0 | 20 | 79.1 |
| 161 | 22.7 | 90 | 41.4 | 19 | 79.9 |
| 160 | 23.1 | 89 | 41.8 | 18 | 80.7 |
| 159 | 23.5 | 88 | 42.1 | 17 | 81.5 |
| 158 | 23.9 | 87 | 42.5 | 16 | 82.4 |
| 157 | 24.2 | 86 | 42.9 | 15 | 83.2 |
| 156 | 24.6 | 85 | 43.3 | 14 | 84.0 |
| 155 | 24.9 | 84 | 43.6 | 13 | 85.2 |
| 154 | 25.3 | 83 | 44.0 | 12 | 86.4 |
| 153 | 25.6 | 82 | 44.4 | 11 | 87.7 |
| 152 | 26.0 | 81 | 44.8 | 10 | 88.9 |
| 151 | 26.3 | 80 | 45.3 | 9 | 90.1 |
| 150 | 26.7 | 79 | 45.7 | 8 | 91.3 |
| 149 | 27.0 | 78 | 46.1 | 7 | 92.6 |
| 148 | 27.4 | 77 | 46.5 | 6 | 93.8 |
| 147 | 27.8 | 76 | 46.9 | 5 | 95.0 |
| 146 | 28.1 | 75 | 47.3 | 4 | 96.7 |
| 145 | 28.5 | 74 | 47.8 | 3 | 98.3 |
| 144 | 28.9 | 73 | 48.2 | 2 | 100.0 |
| 143 | 29.3 | 72 | 48.6 | 1â0 | 101.0 |
| 142 | 29.6 | 71 | 49.0 | ||
| 141 | 30.0 | 70 | 49.5 |