P0A64: Drive Motor A Phase W Current Low

P0A64 means phase W of drive motor A shows too little current at the moment it should peak, typically an open W lead or a W sensor stuck at zero. GM completes its three-phase sequence with this code on the 2016 Chevrolet Volt motor control processor and in the 2018 hybrid tables: when the rotor sits within 30 degrees of the W phase axis, the inverter runs normal PWM above 50 V and the squared current command exceeds 900 A2 (2016) or 4,900 A2 (2018), a W peak below 9 A for 0.4 s of a 0.6 s window sets P0A64 as Type A, MIL on the first trip. Because the rotor passes each axis in turn, only the open phase is flagged. A Caterpillar patent uses a near-zero phase reading the same way. P0A65 is the high side, P0A5E and P0A61 cover U and V.

Symptoms

• MIL and propulsion system warning
• Uneven or reduced electric drive torque

Most likely causes

• Open circuit in the phase W cable, connector or terminal
• Phase W current sensor reads zero
• Phase W switch of the inverter not conducting
• Open winding of phase W in drive motor A

What to check, in order

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

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

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0A64 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• A: Hybrid or air and fuel
• 64: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A64?

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 P0A64?

The most common causes are: open circuit in the phase W cable, connector or terminal; phase W current sensor reads zero; phase W switch of the inverter not conducting.

Related codes

• P0A63Drive Motor A Phase W Current
• P0A65Drive Motor A Phase W Current High
• P0A5EDrive Motor A Phase U Current Low
• P0A61Drive Motor A Phase V Current Low
• P0A6DDrive Motor B Phase W Current Low

Sources

• gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
• gsi.ext.gm.com: 18OBDG01 Hybrid Diagnostics
• patents.google.com: en

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.