Auxiliary Battery Voltage Low
Indicates low voltage in the auxiliary battery circuit.
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What it means (plain English)
The computer sees that the auxiliary battery voltage is below an acceptable level, typically under 11.5 volts, which can cause issues with components powered by this battery.
What the computer is actually seeing
The vehicle computer monitors the auxiliary battery voltage through a voltage reference circuit. When the voltage drops below 11.5 volts for a set period, it triggers this code.
What a healthy reading looks like
Auxiliary battery voltage should be between 12.0 and 14.5 volts when the engine is running.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check auxiliary battery voltage with a multimeter. Expected voltage is 12.0-14.5 volts while the engine is running. If below 11.5 volts, go to step 2.
- 22. Inspect battery terminals for corrosion or looseness. Clean and tighten as necessary. Check voltage again. If still low, go to step 3.
- 33. Test the battery with a load tester. If it fails the test, replace the battery. If it passes, go to step 4.
- 44. Check the charging system, including the alternator output and the voltage regulator. Ensure alternator is providing at least 13.5 volts. If not, repair or replace faulty components.
Common causes
- Low auxiliary battery voltage due to discharge or age
- Corroded or loose battery connections
- Faulty battery or charging system issue
- Defective voltage regulator
- Short circuit in the auxiliary battery wiring
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's advisable to fix this soon since low battery voltage can lead to electrical systems failing, but you may still drive it short distances.
Will this code come back after clearing it?
The auxiliary battery powers systems like the radio, lights, and sometimes the HVAC in newer vehicles.
Working a real vehicle right now?
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