What are the common causes of P0E18?

A short to voltage on the coolant heater B control circuit. A failed heater B control module holding the line high. An open ground at heater B. Water in the heater B connector.

Check the heater B control wire for a short to voltage. Inspect the heater B connector for water and corrosion. Verify the heater B ground. Command heater B with a scan tool and watch it. Replace the heater B module if the line stays high. Clear the code and retest.

P0E18

Hybrid/EV Battery Pack Coolant Heater B Control Circuit High

System: Powertrain control (P code)
Lamp: Check Engine Light
Category: Powertrain - Hybrid Propulsion

What it means

P0E18 means Hybrid/EV Battery Pack Coolant Heater B Control Circuit High.

Check these first

A short to voltage on the coolant heater B control circuit
A failed heater B control module holding the line high
An open ground at heater B
Water in the heater B connector

What to do next

Check the heater B control wire for a short to voltage
Inspect the heater B connector for water and corrosion
Verify the heater B ground
Command heater B with a scan tool and watch it
Replace the heater B module if the line stays high
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.