P00B2: Radiator Coolant Temperature Sensor Circuit Range/Performance
What to do
Check the coolant level yourself, and look at the front of the radiator for leaves, insects or road debris. Both are common, both are free to put right, and both make this sensor report correctly about a genuine cooling problem.
Watch the temperature gauge and say whether it behaves normally, and whether the car has ever run hot. That distinguishes a sensor fault from a real cooling fault, which is the important question here.
Say whether the cooling fan runs when the engine is hot or the air conditioning is on. A fan that never runs produces this and is a different repair.
Leaving the car overnight helps, since this kind of fault is diagnosed from cold when all the temperature sensors should agree.
What this code means
The radiator coolant temperature sensor is reporting a value that is electrically valid but does not fit.
This is not the engine coolant temperature sensor, and the difference is the reason it exists. The engine sensor measures coolant leaving the engine; this one measures coolant leaving the radiator — and the difference between the two is how the module knows whether the radiator and the thermostat are actually working.
That comparison is genuinely powerful. A thermostat stuck open, a radiator blocked internally, a cooling fan not running, or an airlock all show up as the wrong temperature difference across the radiator, without any of them having a sensor of their own.
Range/performance means this sensor's reading does not fit that picture, and the two explanations diverge sharply:
- The sensor has drifted. The cold soak settles it — after standing overnight it must read close to ambient and close to the engine sensor.
- The reading is honest and the cooling system is at fault. Coolant genuinely is not being cooled, or is not flowing.
Do not treat this purely as a sensor code. The consequence of a genuine cooling problem is far more serious than a sensor, and this sensor exists precisely to catch one.
Check the simple things first: coolant level, a radiator blocked externally with leaves and insects, and whether the cooling fan runs. All three are cheap, visible, and produce this reading honestly.
Likely causes
Start here
- Faulty coolant temperature sensor · easy
- Thermostat stuck open · moderate
Less common
- Air trapped in the coolant circuit · moderate
- Blocked or restricted radiator · moderate
- High resistance in sensor wiring · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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