P0E66: Battery Charger Control Circuit Low

With P0E66 the controller finds the charger command line pulled lower than the state it is driving, which typically means the wire touches ground somewhere between the control unit and the on-board charger. If the command is active-high, the charger simply never receives it; a grounded line can also overload the output stage that drives it. No manufacturer documents P0E66 publicly. GM's Volt and 2019 hybrid tables check this line only through the general code P0E65, based on a hardware fault flag sampled every 25 ms at 10.2 V or more. California's OBD rule requires plug-in hybrids to recognise charger faults that stop or limit charging. P0E67 is the opposite case, a line stuck high; P0E68 covers a line that is electrically sound but answers wrongly.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

Charging does not start after plugging in
Charge indicator shows a fault or goes out

Most likely causes

Control wire chafed through to body ground
Moisture in a connector bridging the signal to ground
Internal short in the charger's command input

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
With the connector unplugged, check whether the signal wire is making contact with ground.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

Repair difficulty: medium

What each character of P0E66 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
E: Subsystem depends on the code range
66: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0E66?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0E66?

The most common causes are: control wire chafed through to body ground; moisture in a connector bridging the signal to ground; internal short in the charger's command input.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.