What are the common causes of P0D66?

A short to voltage on the cooling fan enable circuit. An open ground at the fan control module lifting the enable line. A failed fan control module holding the enable high. Water in the fan connector bridging the enable pin.

Check the fan enable wire for a short to voltage. Inspect the fan control module ground. Check the fan connector for water and corrosion. Measure the enable voltage with the key on and the fan commanded off. Replace the fan control module if the enable stays high. Clear the code and retest.

P0D66

Hybrid/EV Battery Pack Cooling Fan Enable Circuit High

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

What it means

P0D66 means Hybrid/EV Battery Pack Cooling Fan Enable Circuit High.

Check these first

A short to voltage on the cooling fan enable circuit
An open ground at the fan control module lifting the enable line
A failed fan control module holding the enable high
Water in the fan connector bridging the enable pin

What to do next

Check the fan enable wire for a short to voltage
Inspect the fan control module ground
Check the fan connector for water and corrosion
Measure the enable voltage with the key on and the fan commanded off
Replace the fan control module if the enable stays high
Clear the code and retest

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Updated

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