P0A0D: High Voltage System Interlock Circuit A High

The voltage sensed on interlock loop A is higher than expected – most often a short to a voltage source, or the loop not being pulled down when the module expects it. GM checks both states: in the 2016 HPC2 table P0A0D sets when the sensed voltage exceeds 24 % of 5 V with the source switched off (5 of 8 samples) or 44 % with it switched on (4 of 6 samples), Type A with MIL after one trip. Hyundai's Sonata Hybrid 2011-2015 bulletins send P0A0D straight to the HEV safety plug, alongside high-voltage path and relay codes, with check engine light and no ready mode. Mercedes model line 243 stores P0A0D00 in the battery management as a short to positive. P0A0C is the low-side counterpart; both leave the HV system switched off.

Symptoms

• No ready mode or ready light blinking
• Check engine and charging warning lights on
• Vehicle cannot be started

Most likely causes

• Service/safety plug not fully inserted or with poor contact (Hyundai Sonata Hybrid)
• Interlock wire shorted to a 12 V or reference voltage
• Damaged interlock harness or connector after body or battery work
• Faulty interlock stage in the battery or hybrid control module

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. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
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

• Repair difficulty: hard
• It can trigger limp mode.

What each character of P0A0D means

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

Frequently asked questions

Can I keep driving with code P0A0D?

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 P0A0D?

The most common causes are: service/safety plug not fully inserted or with poor contact (Hyundai Sonata Hybrid); interlock wire shorted to a 12 V or reference voltage; damaged interlock harness or connector after body or battery work.

Related codes

• P0A0AHigh Voltage System Interlock Circuit A
• P0A0BHigh Voltage System Interlock Circuit A Performance
• P0A0CHigh Voltage System Interlock Circuit A Low
• P0A0EHigh Voltage System Interlock Circuit A Intermittent
• P0D18Battery Charging System A High Voltage Interlock Circuit High

Sources

• gsi.ext.gm.com: 16OBDG02 Hybrid Diagnostics
• static.nhtsa.gov: MC 10241797 0001
• static.nhtsa.gov: MC 11026830 0001

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.