P00B3
Radiator Coolant Temperature Sensor Circuit Low
Engine cooling
Generic OBD-II
High
What it means
P00B3 means the radiator coolant temperature sensor circuit is reading too low — typically a short or a sensor reporting out of range. This sensor (separate from the main engine coolant temp sensor) helps the ECM control the cooling fans, so a fault can throw off fan operation and risk overheating. The engine still starts, but monitor temperature and repair it soon.
High
Can I keep driving? The engine still starts and runs, but faulty fan/temperature control can lead to overheating — watch the temperature gauge and repair before long or hot-weather trips.
Common symptoms
What you'll notice
- Check-engine light on
- Cooling fans running constantly or not switching on when they should
- Engine running hotter than normal or overheating
- Erratic or inaccurate temperature gauge reading
Common causes
Most likely first
- Faulty radiator coolant temperature sensorLikely
- Short-to-ground in the sensor signal wiringCommon
- Corroded or loose sensor connectorCommon
- Cooling-fan relay or wiring fault affecting the circuitLess often
- Less commonly, an ECM/PCM faultLess often
How to diagnose & fix
Work through it in order
- Scan and check the live radiator coolant temperature value for an implausibly low or pinned reading.
- Inspect the sensor and its wiring for a short-to-ground or damaged insulation.
- Check the connector for corrosion and a secure fit.
- Verify the cooling fans switch on and off correctly.
- Replace the radiator coolant temperature sensor if faulty, then clear and retest — address any overheating promptly.
FAQ
Quick answers
Is it safe to drive with P00B3?+
Short trips are usually fine, but because this sensor helps control the cooling fans, keep an eye on the temperature gauge and fix it before it causes overheating.
Can I just clear P00B3?+
You can, but it returns until the sensor or wiring short is repaired. Don't ignore it if the engine is running hot.
Related codes
Often seen with P00B3
Read & clear P00B3 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX