P00B3Radiator Coolant Temperature Sensor Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The radiator coolant temperature sensor is an NTC thermistor that measures coolant temperature on the radiator side, typically at the radiator outlet; the exact position depends on the manufacturer. Together with the engine coolant temperature sensor it gives a second measuring point, which the control module uses to diagnose the thermostat and coolant flow, for example on engines with an electrically heated map-controlled thermostat. P00B3 means the sensor resistance or signal voltage is very low, typically a short to ground; with an NTC sensor the control module then reads an extremely high temperature (around 150 °C in a documented case).
- What you may notice
- Check engine light on
- Thermostat and coolant flow diagnostics are suspended
- Often no noticeable symptoms
- Likely causes
- LikelyConnector or wiring at the radiator corroded or damaged (exposed front position)
- LikelySensor shorted internally
- PossibleSignal wire shorted to ground
- RareEngine control module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €60 – €150
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.