Powertrain, generic · Fuel and air metering, auxiliary emission controls

P00B3 Radiator Coolant Temperature Sensor Circuit Low

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. P00B3 means the sensor resistance or signal voltage is very low, typically a short to ground; with an NTC sensor the control module then reads an extremely high temperature (around 150 °C in a documented case).

Likely causes

Connector or wiring at the radiator corroded or damaged (exposed front position)
Sensor shorted internally
Signal wire shorted to ground
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

P00B1P00B2P00B4P00B5P0117

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.