Engine coolant temperature sensor 5 internally shorted to ground; Signal wire between sensor 5 and the PCM chafed and touching ground; Corroded, loose, or water-intruded connector at sensor 5; PCM internal fault pulling the signal circuit low; Aftermarket sensor with incorrect resistance curve installed; Coolant contamination or low coolant level affecting sensor reading

DTC codes / P2Bxx · Hybrid propulsion / P2B2D

P2B2DEngine Coolant Temperature Sensor 5 Circuit Low

Q: What does code P2B2D mean?

Engine Coolant Temperature Sensor 5 Circuit Low. P2B2D means the powertrain control module (PCM) has detected a low-voltage condition on the signal circuit of engine coolant temperature sensor 5. The PCM expects the sensor's output to stay within a calibrated range, and a sustained low reading tells it the circuit is shorted to ground or the sensor has failed.

P2B2D means the powertrain control module (PCM) has detected a low-voltage condition on the signal circuit of engine coolant temperature sensor 5. The PCM expects the sensor's output to stay within a calibrated range, and a sustained low reading tells it the circuit is shorted to ground or the sensor has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Coolant temperature gauge reads cold or does not move after the engine warms up
Radiator cooling fan runs constantly because the PCM thinks the engine is cold
Poor fuel economy and rich-running exhaust smell from over-fueling
Hard starting or rough idle when the engine is cold
Possible overheating if the fan control strategy is affected

Common causes, most likely first

Engine coolant temperature sensor 5 internally shorted to ground
Signal wire between sensor 5 and the PCM chafed and touching ground
Corroded, loose, or water-intruded connector at sensor 5
PCM internal fault pulling the signal circuit low
Aftermarket sensor with incorrect resistance curve installed
Coolant contamination or low coolant level affecting sensor reading

How to diagnose and fix it

Scan all modules and record freeze-frame data for P2B2D before clearing anything
Inspect sensor 5 connector and harness for corrosion, chafing, or coolant intrusion
Measure sensor resistance cold and hot and compare with the manufacturer's temperature-resistance chart
Backprobe the signal circuit at the PCM and check for a short to ground with the sensor disconnected
Repair or replace the damaged section of signal wire if a short is found
Replace engine coolant temperature sensor 5 if its resistance is out of specification
Clear codes, verify the coolant temperature PID reads realistically during a road test, and confirm the code does not return

Why sensor 5 is not always the culprit

A shorted signal wire is just as common as a failed sensor, so ohm-testing the harness before replacing parts saves money.
Some vehicles use sensor 5 for a secondary cooling loop or transmission cooler, so the reading may not match the primary coolant gauge.
A stuck-open thermostat can mimic a low coolant temperature signal and set this code indirectly on some strategies.
Aftermarket sensors with the wrong resistance curve frequently set this code even though they are new.
The PCM may default to a fixed coolant temperature value, masking the fault and making the engine run rich without an obvious driveability complaint.

Can I keep driving with P2B2D?

You can usually drive short distances to a repair shop, but avoid heavy loads and long trips because the PCM may over-fuel the engine and the cooling fan may run continuously. If the temperature gauge climbs above normal, stop and shut the engine off.

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.