What it means
The control module monitors the radiator coolant temperature sensor circuit to assess coolant temperature. It sets this code when it detects a fault in that circuit; the code alone does not specify whether the sensor signal is too high, too low, or otherwise faulty.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The radiator coolant temperature sensor sends a temperature signal to the control module, which uses it to assess cooling-system operation and help manage the fan. P00B1 sets when the module detects a fault in this sensor circuit; the code does not say whether the signal is high, low, or erratic.
Common causes
Most likely first.
- Radiator coolant temperature sensor failed
- Loose, corroded, or damaged connector
- Open or shorted wiring
- Fault in the control module circuit
Symptoms
- Check engine light on
- Temperature gauge may read incorrectly or fluctuate
- Cooling fan may run unusually or not operate as expected
How to diagnose it
- Record freeze-frame data and compare radiator coolant temperature with engine coolant temperature and ambient temperature when the engine is cold for readings that do not make sense.
- Locate the radiator coolant temperature sensor and inspect its connector and nearby wiring for corrosion, looseness, damage, or coolant intrusion.
- With a scan tool, watch the radiator sensor reading from a cold start and during warm-up for a missing or implausible signal.
- Check the sensor circuit for continuity, shorts, and connector contact problems using the manufacturer's wiring diagram and specifications.
- Test the radiator coolant temperature sensor and, if its circuit and sensor pass, investigate the control module circuit.
Common fixes
- Reconnect or clean the radiator coolant temperature sensor connector.
- Repair an open, shorted, or damaged section of sensor wiring.
- Replace the radiator coolant temperature sensor if it fails the specified test.
- Repair the control module circuit only after the sensor and wiring have been verified.
Can I keep driving?
If the temperature gauge behaves unusually or the cooling fan does not operate as expected, monitor engine temperature closely and avoid driving if it rises above normal. Overheating can cause serious engine damage.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.