P0D21: Battery Charger Output Voltage Too Low
Severity: medium
What it means: A plug-in hybrid or EV code that sets when the onboard battery charger's output voltage is lower than expected, so the high-voltage battery doesn't charge properly. On Jeep 4xe models it shows up with charging-module (IDCM) faults, and Jeep has issued IDCM software update bulletins for charging problems.
Safe to drive? Usually drivable on gas or remaining charge, but the car may not charge. Get it checked soon, and follow any recall instructions about charging.
Common symptoms
- Won't charge or stops charging
- Service Charging System or similar warning
- Check engine light
Likely causes, ranked
- Charging module (onboard charger) software or internal faultShop
- Weak or interrupted AC supply from the outlet or chargerDIY
- Wiring or connector problem in the charging systemShop
Vehicle-specific notes
- 2022–2025 Jeep Grand Cherokee 4xe: Logged together with B22A9 on a 2024 4xe that wouldn't charge. Read the full answer · Source
DIY or shop?
Testing another outlet or charger is DIY. Charging-module diagnosis and software updates are for a dealer.
Before you replace parts
- Try a different outlet, circuit and charger.
- Check your VIN for recalls and charging-module software bulletins.
- Read all codes. B22A9 with P0D21 points to the charging module.
- Don't keep retrying a charger that trips or overheats.
Safety / mechanic note
Verify with a mechanic. High-voltage charging systems can be dangerous. Leave them to a trained technician. A code points to a circuit or system, not always a specific part.