Powertrain, generic (extended)

P2B20 Hybrid/EV Electronics Coolant Temperature Sensor B Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Sensor B is a second temperature sensor in the coolant loop that serves the hybrid or EV power electronics, such as inverter, DC/DC converter or on-board charger; where it sits relative to sensor A is up to the vehicle maker. P2B20 is the undifferentiated circuit code: the controller finds the signal unusable without deciding between low and high. No manufacturer documents P2B20 publicly. Supplier NTN-SNR lists it in its coolant sensor catalogue as an electrical fault in the sensor B circuit, and CARB requires every input of inverter thermal management to be checked for circuit faults. GM's handling of sensor A (P0CF0/P0CF1 in its 2019 HPC2 table) shows the usual NTC logic behind such checks. Without the reading, the system tends to cut inverter and charging power.

Likely causes

Loose connector, corroded pins or broken wire in the sensor B circuit
Sensor B element open or shorted internally
Faulty input stage or reference supply in the controlling module

Symptoms

  • Hybrid or EV system warning and stored fault code
  • Reduced drive or charging power as a precaution
  • Electronics coolant pump running more often or at higher speed

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–400
Time0.5–2 h

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

Parts involved

hybrid electronics coolant temp sensor bwiring harnesshybrid control module

Related codes

P2B21P2B22P2B23P2B24P0CEEP2D2A

References: law.cornell.edu, ntn-snr.com, gsi.ext.gm.com.