What it means
The battery monitor reports a State of Charge (SoC) value that does not match the rest-voltage and current pattern - typically a battery near end of life, sulfation, or a deep discharge that the SoC algorithm has not converged on.
At a glance
- Usually lights the check-engine light
How it works
The battery monitor estimates Battery A's state of charge from battery voltage and current over time. This code sets when the reported charge does not fit the battery's measured rest voltage and current pattern, which can happen with a worn or deeply discharged battery or a faulty monitor signal.
Common causes
Most likely first.
- Battery aged, sulfated, or at end of service life
- Battery deeply discharged
- Battery monitor sensor or wiring fault
- Poor battery terminal connection
Symptoms
- Check-engine or battery warning light may come on
- Stop-start system may be unavailable, if equipped
- Slow or difficult engine starting
- Electrical accessories may operate erratically
How to diagnose it
- Review freeze-frame data and battery or charging-system codes first to see whether the fault followed a deep discharge or low-voltage event.
- With the vehicle off, inspect Battery A's case and terminals for damage, looseness, corrosion, or poor contact.
- Check Battery A's resting voltage and condition using the vehicle maker's battery test procedure, then compare the result with the monitor's reported state of charge.
- Check charging voltage and current with the engine running to rule out a charging problem affecting the monitor's estimate.
- Inspect the battery-monitor sensor, its connector, and wiring for damage or poor connections, and compare its live data with measured battery behavior.
Common fixes
- Clean and secure Battery A's terminals and connections.
- Fully recharge a deeply discharged battery, then allow the monitor to relearn if the vehicle procedure requires it.
- Replace Battery A if it fails the manufacturer's battery condition test.
- Repair damaged battery-monitor wiring or connector terminals.
- Replace a faulty battery-monitor sensor if its readings remain implausible after wiring checks.
Can I keep driving?
If the engine starts reliably and there are no other electrical warnings, a short necessary trip may be possible, but avoid relying on stop-start or other high electrical loads. A weak or discharged battery can leave you unable to restart, so address slow cranking or erratic electrical behavior promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.