P0A8D: 14 Volt Power Module System Voltage Low

P0A8D reports too low a voltage at the 14 V power module (DC/DC converter feeding the 12 V network). GM uses it in its 2013 eAssist tables as the circuit-low check of the APM low-voltage sensor: if that sensor reads below 1 V for 1.5 s within a 2 s window while ignition voltage is 9 to 32 V, the code sets; it passes again above 1.5 V. It is Type B, two trips to MIL. Because a real 12 V network cannot be at 1 V with the ignition on, GM's version really points to an open or shorted voltage sense line or a failed sensor, not a flat battery. Other makers may apply the code to genuine undervoltage. P0A8E is the high counterpart, P0A8F the correlation check.

Medium severity. Can I keep driving?If the battery warning light comes on, you could get stranded. Turn off electrical accessories and go straight to a repair shop.

Symptoms

MIL and charging/hybrid warning
12 V battery discharges
Start/stop disabled

Most likely causes

Voltage sense line open or shorted to ground
Voltage sensor inside the power module failed
Converter not delivering output (fuse, output cable)

What to check, in order

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

Measure the voltage with the engine off and running
With the connector unplugged, check whether the signal wire is making contact with ground.
Clean and tighten the terminals
Check the accessory belt
Run a battery load test
Check the alternator wiring

Good to know

It affects emissions.

What each character of P0A8D means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
8D: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A8D?

If the battery warning light comes on, you could get stranded. Turn off electrical accessories and go straight to a repair shop.

What causes code P0A8D?

The most common causes are: voltage sense line open or shorted to ground; voltage sensor inside the power module failed; converter not delivering output (fuse, output cable).

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.