Powertrain, generic · Fuel and air metering, auxiliary emission controls
P00B5 Radiator Coolant Temperature Sensor Circuit Intermittent/Erratic
Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo
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. P00B5 is set when the signal jumps or drops out briefly, which typically points to a loose contact. No manufacturer description naming this exact code was found.
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
Symptoms
- Check engine light on
- Thermostat and coolant flow diagnostics are suspended
- Often no noticeable symptoms
Repair estimate
DifficultyEasyDIY possible
Parts and labour€60–150
Time0.3–1 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
radiator coolant temperature sensorradiator coolant temperature sensor wiring
Related codes
References: law.cornell.edu, en.wikipedia.org, en.wikipedia.org.