05 Sensors
CLT & IAT
NTC calibration, pull-up, and where to put the sensors.
5 min readUpdated 2026-08
Coolant (CLT) and intake air (IAT) are two-wire NTCs on the analog-temp inputs. Default: IAT on AT 2 (C30), CLT on AT 4 (C31). The ECU provides the 5 V pull-up (typically 2.7 kΩ).
Where they go
- CLT: in the head or a thermostat housing that actually sees metal temperature, not a radiator hose that reads 20 °C cold all winter.
- IAT: post-intercooler in the pipe or in the manifold. A sensor in the airbox measures ambient, not charge temp — your VE will be wrong in boost.
- Oil temp (optional) on AT 1. Useful for protection and for dead-time vs oil temp on a race engine.
Calibration
Enter the three-point or full curve from the sensor (GM, Bosch, Nissan, standard Race Core NTC). Then verify:
| Condition | What you should see |
|---|---|
| Engine stone cold, open bay | CLT ≈ IAT ≈ ambient (within a few degrees) |
| Hot idle | CLT at thermostat (82–95 °C typical); IAT a bit above ambient |
| Unplugged AT | Reading rails to extremely cold / open — confirms pull-up, not a short |