OBD-II trouble code
U0412: Invalid Data Received From Battery Energy Control Module A
Battery energy control module A is still on the network, but a value it reports has been rejected. Most often that value is state of charge, which is estimated rather than measured — so this is frequently a drifted calculation rather than a failed pack. High-voltage system: professional diagnosis.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,500
- DIY difficulty
- Shop recommended
Part of a 2-code family
U0412 is one of 2 codes covering invalid data received from battery energy control module. The letter is the slot number your manufacturer assigned — it is not a physical difference, and the same letter means different things on different makes. The diagnosis is the same for every code in the family.
Read the full guide for this family →Browse every code in U0401–U0478, or start from the full code library.
What does U0412 mean?
The instinct on seeing a high-voltage battery code is to think about the pack. On U0412 that instinct is usually wrong, and the reason is worth understanding before anyone quotes anything.
Battery energy control module A is the supervisor of the traction pack — or of one section of it, on designs that split a large pack between several supervisors and letter them A, B and onward. It watches individual cell voltages and temperatures, measures pack current, decides how much power may be drawn or accepted at any moment, and controls the contactors that physically connect the pack to the rest of the car. U0412 means another module is still receiving its messages but has rejected the contents.
The rejected value is very often state of charge, and state of charge has a property that separates this code from every other invalid-data fault in the range: it is not measured. Nothing in a battery reports how full it is. The module estimates it, by integrating current in and out over time and correcting that running total against cell voltage whenever the pack is resting. That is a calculation with memory, and calculations with memory drift. A disconnected 12-volt battery, a long period standing at very low charge, a cell that has aged out of step with its neighbours, or simply a car that is never left at rest long enough for a proper voltage correction will all pull the estimate away from reality. The module then broadcasts a number that other modules can prove is wrong — the range says forty percent while the pack behaves like ten — and the fault is stored. Nothing has broken. The bookkeeping has diverged, and on many vehicles a guided relearn or a controlled full charge and rest cycle is the actual repair.
That produces the symptoms owners describe, which are about energy rather than performance. The charge gauge jumps in steps instead of falling smoothly. Predicted range swings wildly between journeys. Charging stops early, or refuses to begin, because the module will not authorise a session it cannot account for. The usable window shrinks: the car reserves margin at both ends to protect against an estimate it no longer trusts, so a full charge delivers noticeably less than it used to.
There is one much less convenient possibility to know about. This module is the gatekeeper for closing the high-voltage contactors, and it will not close them on data it cannot validate. When that happens the car does not go into a reduced-power mode — it simply refuses to become ready. Dash lights come on, everything low-voltage works, and nothing happens when you press the button. That presentation is routinely mistaken for a flat 12-volt battery, and jump-starting it changes nothing, because the pack was never invited to connect.
Finally, the letter matters commercially. On a pack divided into lettered sections, A identifies which supervisor complained, and that narrows the investigation to one section rather than condemning the whole pack. Diagnosis belongs with a qualified hybrid or EV technician.
Common causes
- Failing cell-voltage sense line or module feeding implausible pack data
- Pack temperature sensor or high-voltage current sensor fault producing out-of-range values
- Low 12-volt system voltage or a weak auxiliary battery
- Outdated, corrupted, or mismatched battery energy control module software
- Module or high-voltage pack serviced/replaced without proper programming
- Electrical noise or damaged bus wiring corrupting messages in transit
- Battery energy control module internal fault
- Corrosion or a loose connection at the module's low-voltage connector
Symptoms
- State-of-charge gauge falling in steps rather than smoothly, or jumping between readings
- Predicted range swinging widely between journeys
- Charging stopping early, or refusing to start at all
- A full charge delivering noticeably less than it used to, as the car reserves margin at both ends
- Vehicle refusing to become ready — dash lights on, low-voltage systems working, nothing happening on the start button — which is routinely mistaken for a flat 12-volt battery and is not cured by jump-starting
- Charging or regenerative braking limited or disabled
- Hybrid system or master warning light illuminated
- Reduced power or a protective 'turtle'/limp mode where the pack is allowed to connect at all
- Hybrid leaning more heavily on its gasoline engine
- Companion battery, cell, or contactor codes stored alongside U0412
- Vehicle often still driveable in a reduced state
Diagnostic steps
- 1.Read ALL stored codes first — U0412 is often secondary to a battery cell, temperature, or contactor code that names the bad signal.
- 2.Check the 12-volt battery and charging system; low auxiliary voltage is a common cause of implausible module data even on high-voltage vehicles.
- 3.Use a capable scan tool to review cell voltages, pack temperature, current, and state-of-charge for out-of-range values.
- 4.Inspect the module's low-voltage connectors and bus wiring for corrosion or damage (leave high-voltage service to qualified technicians).
- 5.Verify the battery energy control module has the correct, current calibration, especially after any pack or module service.
- 6.Address any companion codes before condemning the module; the underlying fault often clears U0412.
Repair cost
$100 – $1,500
Cost varies with the fault and is wider than most invalid-data codes because high-voltage hardware is expensive. A software reflash runs $100-$300, and correcting a weak 12-volt battery or charging fault $150-$600. A sensing component or harness repair typically runs $250-$800 with diagnosis. Battery energy control module replacement with programming is the high end — often $900-$1,500 or more on some platforms — and should only follow thorough diagnosis at a qualified hybrid/EV shop, since U0412 is frequently a secondary code.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with control module replacement & programming preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. The barrier here is module programming, security access, and bus-level diagnosis that need manufacturer-grade scan tools and the credentials to use them. DIY attempts often produce a more expensive problem than the original code.