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. P00B1 is the general circuit fault; low and high signals have their own codes. No manufacturer description naming this exact code was found.
Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.
Symptoms
- Check engine light on
- Thermostat and coolant flow diagnostics are suspended
- Often no noticeable symptoms
Most likely causes
- Connector or wiring at the radiator corroded or damaged (exposed front position)
- Sensor faulty
- Loose contact in the circuit
- Engine control module faulty
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
- It affects emissions.
What each character of P00B1 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 0: Subsystem depends on the code range
- B1: Specific fault in that system
Frequently asked questions
Can I keep driving with code P00B1?
Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.
What causes code P00B1?
The most common causes are: connector or wiring at the radiator corroded or damaged (exposed front position); sensor faulty; loose contact in the circuit.
Related codes
- P00B2Radiator Coolant Temperature Sensor Circuit Range/Performance
- P00B3Radiator Coolant Temperature Sensor Circuit Low
- P00B4Radiator Coolant Temperature Sensor Circuit High
- P00B5Radiator Coolant Temperature Sensor Circuit Intermittent/Erratic
- P00B6Radiator Coolant Temperature/Engine Coolant Temperature Correlation
- P0115Engine Coolant Temperature Sensor 1 Circuit
Sources
- law.cornell.edu: 13 CCR 1968.2
- en.wikipedia.org: Thermistor
- en.wikipedia.org: Radiator (engine cooling)
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.