Coolant Temperature
Coolant temperature (CLT) is used by idle target and correction tables, cranking and warm-up fuel, coolant timing correction, fan control, coolant-based limits, and charge-temperature estimation. A valid calibration therefore affects far more than the temperature gauge.
Configuration and calibration
Open Sensors > CLT sensor. Assign Input channel and Pullup resistor, then enter Lowest, Middle, and Highest temperature with the corresponding resistances (CLT dialog). A Common CLT Sensors selector fills known curves for GM, Miata, and Bosch sensors, but verify that the installed sensor matches the chosen option.
The resistance-to-temperature conversion uses all three calibrated points. Temperatures must be strictly ascending (validation). Enable Linear characteristic only for a sensor whose resistance-to-temperature relationship is intentionally represented by the first two linear points. Set the pull-up value from the exact board circuit, not from another board revision. CLT sensor is pulldown instead of pullup changes the resistance calculation for a board wired that way.
At a cold start and at a known warm operating point, compare Coolant temp with a trusted reference. Also watch Raw CLT while moving or disturbing the harness to detect intermittent connection.
Wiring and diagnostics
Connect the two-wire thermistor to a board-supported analog-temperature input, sensor ground, and the documented bias supply. The Universal 112 v1.2 documents four analog temperature inputs and its pull-up arrangement in the revision-specific pinout; other boards require their own documentation.
Sensor Checker maps CLT timeout, low, and high conditions to P0115, P0117, and P0118 (DTC mapping). Do not treat a failed CLT as a normal warm engine: different consumers have different fallbacks. Correct the input and calibration before tuning dependent tables.