P2B23

Code

Generic P — Powertrain

Hybrid/EV Electronics Coolant Temperature Sensor B Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 41 EN: 49 RU: 23

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Page language: EN

Causes

Open circuit in sensor B wiring (broken wire, connector disconnected)
Short to voltage (battery+) on sensor B signal wire
Poor or corroded connector or pin at sensor or ECU
Faulty coolant temperature sensor (Sensor B)
Low coolant level or air in cooling loop causing sensor exposure
High resistance in ground or reference circuit

Symptoms

Malfunction indicator lamp (MIL) or hybrid system warning illuminated
Possible reduced inverter/charge cooling performance or limp-home mode
Incorrect temperature readout for inverter/cooling system B (if displayed)
Cooling fan or pump may run abnormally if controller uses sensor input
Diagnostic trouble code P2B23 stored

What to check

Retrieve freeze-frame and live data for sensor B and compare with sensor A and ambient temp
Visually inspect sensor B connector, pins, and harness for damage or corrosion
Check coolant level and look for air pockets in the electronics cooling circuit
Back-probe sensor connector to measure signal voltage and reference voltage with ignition ON (engine/off)
Measure sensor resistance at ambient temperature (disconnect sensor)
Check continuity to the ECU/inverter connector; verify no short to battery or ground

Signal parameters

Typical sensor type: NTC thermistor (resistance decreases as temperature rises) or 0–5 V temperature sender (vehicle-specific)
Expected signal voltage (vehicle-dependent): roughly 0.2–4.8 V under normal temperatures; a reading near battery voltage (>4.5 V) often flags 'High'
Expected resistance (NTC) at ~20–25 °C often in the kilohm range (example 1–10 kΩ) — check vehicle spec
Open-circuit or a high-voltage signal indicates circuit high/failed sensor
Reference voltage from ECU commonly ~5 V; ground should be near 0 V

Diagnostic algorithm

Read and record freeze-frame and live data for both electronics coolant sensors and related temps. Note conditions when code set.
Visually inspect sensor B connector, pins and harness for corrosion, damage, water ingress or disconnection. Repair any damage.
Verify coolant level and eliminate air from the electronics cooling circuit. Re-test if low coolant or air was found.
With connector connected, back-probe the signal, reference and ground pins. With ignition ON (engine off), measure signal voltage and reference voltage against vehicle ground. Compare to expected ranges.
With sensor disconnected, measure resistance of the sensor at ambient temperature and compare to specification. If reading is open/infinite or far out-of-spec, replace sensor.
Check continuity and resistance of the harness between sensor and ECU/inverter; look for opens or shorts to battery voltage or ground. Repair any wiring faults.
If signal reads high at the ECU pin but sensor and harness are good (no short to battery and sensor tests OK), verify ECU/inverter reference output and ground integrity. Replace ECU only after confirming wiring and sensor are good.
After repair, clear codes, perform a test drive or operate hybrid system to verify code does not return and that live temperature readings are plausible.

Likely causes

Open circuit or disconnected connector on sensor B harness
Corroded/loose connector or poor pin contact
Sensor B failed (open or out-of-spec)
Short to battery voltage on the sensor signal
Faulty reference/ground or ECU driver

Fault status

⚠️ Status

Hybrid/EV electronics coolant temperature sensor B circuit reports a high or out-of-range signal (possible open, short to voltage, sensor failure, or wiring/connector fault).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours