Open circuit in the coolant heater element itself (failed heater); Broken or corroded wiring between the heater and the control module; Blown fuse or open fusible link supplying the heater circuit; Faulty coolant heater control module or relay; Loose or damaged connector at the heater or control module; High resistance in the ground circuit for the heater; Internal open circuit in the battery energy control module (less common)

DTC codes / P0Exx · Hybrid propulsion / P0E16

P0E16Hybrid/EV Battery Pack Coolant Heater B Control Circuit/Open

P0E16 is a generic powertrain code indicating that the hybrid or electric vehicle battery pack coolant heater control circuit for channel B is open. The battery energy control module (BECM) or dedicated heater controller has detected an open circuit, meaning no current can flow through the heater element or its wiring when activation is commanded.

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 in mild weather
Reduced hybrid/EV battery performance or power output in cold temperatures
Longer charging times or inability to precondition the battery
Battery temperature warning or reduced regenerative braking
Possible no-start condition in extreme cold if battery heating is required

Common causes, most likely first

Open circuit in the coolant heater element itself (failed heater)
Broken or corroded wiring between the heater and the control module
Blown fuse or open fusible link supplying the heater circuit
Faulty coolant heater control module or relay
Loose or damaged connector at the heater or control module
High resistance in the ground circuit for the heater
Internal open circuit in the battery energy control module (less common)

How to diagnose and fix it

Verify the code with a scan tool and check for any related codes in the hybrid/EV system
Inspect the coolant heater fuse and relay, replacing if blown or faulty
Visually inspect the heater wiring harness and connectors for damage, corrosion, or looseness
Measure resistance of the heater element with a multimeter and compare to specification
Check for voltage and ground at the heater connector when activation is commanded
Test the control module output signal and repair or replace as needed
Clear codes and perform a road test or activation test to confirm the repair

Coolant heater circuit checks before replacement

An open circuit code often results from a simple blown fuse or unplugged connector rather than a failed heater element, so always check those first.
The coolant heater may only activate under specific conditions such as low ambient temperature or during battery preconditioning, so the fault may not appear during a warm-weather test.
Some vehicles use a relay or solid-state controller that can fail open without setting a separate relay code, so testing the control side is essential.
A faulty ground connection can mimic an open heater circuit, so voltage drop testing on the ground side is a critical step.
This code does not always mean the heater is defective; wiring damage from rodent activity or chafing is a common hidden cause.

Can I keep driving with P0E16?

You can generally continue driving, but avoid heavy electrical loads and cold-weather operation that relies on battery heating. Prolonged driving with the fault may reduce battery performance or cause other system faults, so schedule diagnosis soon.

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.