Faulty battery pack coolant temperature sensor C; Damaged or chafed wiring in the sensor C circuit, especially near the battery pack or harness connectors; Corroded, loose, or water-intruded connector at the sensor or control module; Open or high-resistance ground connection for the sensor circuit; Internal fault in the battery energy control module or its signal processing circuit; Coolant contamination or low coolant level causing the sensor to read out of range; Aftermarket or incorrect sensor installed during previous repairs

DTC codes / P2Dxx · Hybrid propulsion / P2D54

P2D54Hybrid/EV Battery Pack Coolant Temperature Sensor C Circuit Low

P2D54 indicates that the hybrid or electric vehicle battery pack coolant temperature sensor, specifically the 'C' circuit, is reporting a voltage or signal that is lower than the manufacturer's expected range. The battery energy control module monitors this sensor to protect the high-voltage battery from overheating or overcooling, and it sets this code when the signal on the C circuit falls below the calibrated threshold for a set time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service vehicle soon message
Often no symptoms besides the warning light, especially if the fault is intermittent
Reduced hybrid system power or a forced limp mode in some vehicles
Battery cooling fan may run continuously or not at all
Possible drop in fuel economy or electric range if the system limits battery usage
In rare cases, a message to pull over safely due to battery temperature management failure

Common causes, most likely first

Faulty battery pack coolant temperature sensor C
Damaged or chafed wiring in the sensor C circuit, especially near the battery pack or harness connectors
Corroded, loose, or water-intruded connector at the sensor or control module
Open or high-resistance ground connection for the sensor circuit
Internal fault in the battery energy control module or its signal processing circuit
Coolant contamination or low coolant level causing the sensor to read out of range
Aftermarket or incorrect sensor installed during previous repairs

How to diagnose and fix it

Scan all modules and record freeze-frame data for P2D54 and any related codes before clearing anything
Visually inspect the sensor, its connector, and the wiring harness for damage, corrosion, or coolant intrusion
Measure the sensor resistance and compare it to the manufacturer's temperature-resistance chart for the current coolant temperature
Backprobe the sensor C circuit at the control module connector and check for a short to ground or an open circuit
Verify the sensor ground circuit has less than 0.1 volts of voltage drop under load
If the wiring and sensor test good, substitute a known-good sensor and recheck live data to confirm the fix
Clear codes and perform a road test with the battery cooling system active to verify the code does not return

Coolant sensor C circuit traps to avoid

A low signal code often comes from a short to ground in the harness rather than a failed sensor, so ohm-testing the wire before replacing parts saves time and money.
Some vehicles set P2D54 when the battery pack coolant is simply low or aerated, causing the sensor to read outside its expected range even though the sensor itself is fine.
Technicians sometimes replace the sensor only to find the connector pins have been pushed back or corroded, so always perform a drag test on the terminals.
The battery energy control module may share the sensor ground with other temperature sensors, so a single bad ground can set multiple coolant temperature codes at once.
Intermittent P2D54 codes that appear only in cold weather often trace to a harness that stiffens and pulls on a marginal connector at the battery pack.

Can I keep driving with P2D54?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration, long grades, and fast charging because the battery cooling system may not be able to protect the pack. If the vehicle enters a reduced-power mode or displays a stop-driving warning, pull over 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.