Powertrain, generic (extended)

P2BD9 Motor Electronics Coolant Temperature Sensor B Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2BD9 means coolant temperature sensor B in the motor electronics loop delivers a voltage inside its electrical window, yet the temperature it reports does not fit the rest of the vehicle. The circuit itself is intact; a drifting thermistor, a sensor sitting in an air pocket or a value that stays frozen are typical. No manufacturer documents P2BD9 publicly. GM's method for sensor A on the 2013 Two-Mode hybrid trucks, P0A01, shows the principle: after the vehicle has rested for over 28,800 s, the loop temperature at power-up may differ from engine coolant temperature by no more than 30 °C, provided engine coolant and intake air agree within 15.75 °C; a failure counts as Type B. Voltages outside the window for this sensor are reported as P2BDA and P2BDB; sensor C has its own check, P2BDD.

Likely causes

Sensor B thermistor drifted out of its characteristic
Air pocket or low coolant leaving sensor B partly dry
Added resistance from corroded terminals shifting the reading
Wrong value from a comparison sensor such as engine coolant or intake air temperature

Symptoms

  • Check engine light, usually without a noticeable driving issue at first
  • Cooling fan or electronics pump running at unexpected times
  • Occasional power limitation on hot days

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–500
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

motor electronics coolant temp sensor bwiring harnesshybrid control module

Related codes

P2BD8P2BDAP2BDBP2BDDP0A01

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