What are the common causes of P0D21?

A battery charger A output voltage that reads too low. A resistive short in the charging bus. A failed battery charger A. A poor connection at the charger output.

Read battery charger A output voltage on a scan tool. Compare charger output against the hybrid/EV battery pack voltage. Inspect the charger output connectors and charging bus. Test the charging bus for a resistive short. Replace the battery charger if output stays too low. Clear the code and retest.

P0D21

Battery Charger A Output Voltage Too Low

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

What it means

P0D21 means Battery Charger A Output Voltage Too Low.

Check these first

A battery charger A output voltage that reads too low
A resistive short in the charging bus
A failed battery charger A
A poor connection at the charger output

What to do next

Read battery charger A output voltage on a scan tool
Compare charger output against the hybrid/EV battery pack voltage
Inspect the charger output connectors and charging bus
Test the charging bus for a resistive short
Replace the battery charger if output stays too low
Clear the code and retest

Look up another code

Code or symptom

Enter a full code or a symptom. Press / to search. How to read a code

Type a code above, or start from a symptom or a common code.

Updated

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