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DTC codes / P2Bxx · Hybrid propulsion / P2B22

P2B22Hybrid/EV Electronics Coolant Temperature Sensor B Circuit Low

P2B22 means the hybrid or electric vehicle control module has detected an abnormally low voltage signal from the coolant temperature sensor that monitors the electronics cooling loop, identified as sensor B. The circuit is reading below the expected range, which tells the computer the coolant is colder than it physically can be or that the sensor circuit is shorted to ground.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the hybrid system warning light or a generic check engine light
  • Often no symptoms besides the warning light, especially in mild weather
  • Reduced electric power output or a forced limp mode if the module derates the system
  • Cooling fans running continuously at high speed because the module defaults to a safe strategy
  • Overheating warnings or shutdown of the hybrid/EV system in extreme cases
  • Slightly reduced fuel economy on hybrid models as the system limits electric assist

Common causes, most likely first

  1. A short to ground in the sensor signal wire, often from chafing against a bracket or heat shield
  2. A failed coolant temperature sensor B whose internal thermistor has shorted
  3. Corroded or pushed-back pins in the sensor connector or the control module connector
  4. Coolant intrusion into the sensor connector or wiring harness from a leaking housing
  5. A faulty hybrid/EV control module with an internal pull-down on the sensor circuit
  6. A pinched harness during previous service work near the cooling loop

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P2B22 to confirm the signal was low when the fault set
  2. Inspect the sensor B connector and harness for corrosion, coolant residue, or chafed wiring
  3. Disconnect the sensor and measure resistance across its terminals, comparing to the manufacturer's temperature chart
  4. With the sensor unplugged, check the signal wire for continuity to ground with the key off to rule out a short
  5. Back-probe the signal circuit at the module and compare voltage with the sensor connected and disconnected
  6. Repair or replace the faulty sensor, pigtail, or harness section and clear the code
  7. Verify the repair by watching live coolant temperature data through a warm-up cycle and confirming the code does not return

Why this code often is not the sensor

  • A shorted sensor is less common than a harness rubbed through near the electronics coolant pump or radiator shroud, so inspect the loom before condemning the sensor.
  • Sensor B often monitors a second point in the same cooling loop, so a low reading can be caused by a connector that was left unplugged during a recent coolant service.
  • The module may substitute a default coolant temperature and keep the vehicle driving normally, which hides the fault until the next cold start or a long high-load drive.
  • Coolant residue inside the connector can bridge the signal pins and mimic a failed sensor, so clean and dry the connector before testing resistance.
  • A low signal does not always mean the coolant is cold; a short to ground pulls the reading down regardless of actual temperature, so never trust the dash gauge alone.

Can I keep driving with P2B22?

You can usually drive the vehicle short distances to a repair shop, but avoid sustained high-speed driving or heavy loads because the module may not accurately control electronics cooling. If the hybrid system warning light is accompanied by a power reduction or overheating message, stop and have the vehicle towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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