Open or damaged wiring in the sensor B signal circuit, including a broken wire or poor connector terminal; Sensor B internal failure causing an open circuit or a signal stuck at the high voltage limit; Corrosion or water intrusion at the sensor connector or inline harness connector; Short to voltage on the signal circuit from chafed wiring near the power electronics or coolant lines; Failed or unplugged sensor B ground circuit, which drives the signal voltage high; Control module internal fault on the sensor input circuit, though this is less common

DTC codes / P2Bxx · Hybrid propulsion / P2B23

P2B23Hybrid/EV Electronics Coolant Temperature Sensor B Circuit High

P2B23 means the hybrid or electric vehicle's electronics coolant temperature sensor B circuit is reporting a voltage higher than the manufacturer's expected range, so the control module cannot trust the reading. The computer has detected an open circuit, a short to voltage, or a sensor signal that stays above the normal threshold, which can affect cooling system management and power electronics protection.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the hybrid or EV system warning light, often with no other noticeable symptoms
Reduced power output or a limp-home mode as the vehicle protects the power electronics
Cooling fans running continuously or not at all, depending on the default strategy
Overheating warnings or a message to stop the vehicle if the coolant temperature is genuinely high
Inconsistent or disabled cabin climate control in some designs that share the electronics cooling loop

Common causes, most likely first

Open or damaged wiring in the sensor B signal circuit, including a broken wire or poor connector terminal
Sensor B internal failure causing an open circuit or a signal stuck at the high voltage limit
Corrosion or water intrusion at the sensor connector or inline harness connector
Short to voltage on the signal circuit from chafed wiring near the power electronics or coolant lines
Failed or unplugged sensor B ground circuit, which drives the signal voltage high
Control module internal fault on the sensor input circuit, though this is less common

How to diagnose and fix it

Scan all modules and record freeze-frame data for P2B23, then verify the sensor B voltage reading with a live data scan tool
Inspect the sensor B connector and harness for corrosion, water intrusion, loose terminals, and chafed wiring
Measure resistance across sensor B at the connector and compare with the manufacturer's temperature-resistance chart
Check the sensor B signal circuit for a short to voltage and the ground circuit for continuity back to the control module
Backprobe the control module connector to confirm the signal voltage matches the sensor reading and rule out a module fault
Replace the faulty sensor or repair the damaged harness section, then clear the code and verify the reading returns to normal
Perform a road test with live data to confirm the coolant temperature rises and falls correctly and the code does not return

What the high voltage reading really means

A high voltage on a temperature sensor circuit almost always means an open circuit or a disconnected sensor, not an actual overheating event, so do not replace cooling system parts before checking the wiring.
Some vehicles use two coolant temperature sensors for the electronics loop, and sensor B may be the outlet sensor; a failed sensor A can cause the module to set a related code for B if the strategy cross-checks the two readings.
Water intrusion at the sensor connector is a common cause on hybrid and EV models because the sensor sits near splash zones or underbody panels, and the corrosion can mimic an open circuit.
The control module may default to a fixed coolant temperature value when the circuit is high, which can disable active grille shutters or cooling fan control and cause a secondary complaint that seems unrelated.
A short to voltage on the signal wire can be caused by a chafed harness rubbing against a metal bracket near the power electronics, so a visual inspection of the full harness route is essential.

Can I keep driving with P2B23?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, long trips, or high ambient temperatures because the control module may not be able to protect the power electronics properly. If the vehicle enters limp mode or shows an overheating warning, stop safely and have it towed.

Tools that help

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