Warning lights & codes
Hybrid battery fault codes and hybrid warning lights
What the light or code actually means, what could cause it, what a proper diagnostic process checks, and — importantly — what not to do next. Toyota and Lexus in the most depth, plus Honda IMA, Hyundai, Kia, Ford and GM two-mode codes.
Read this first
Do not replace parts based on a code alone. A diagnostic trouble code tells you which circuit or system reported a problem — it does not identify which component failed. The same code can be set by several different faults, and clearing it without a diagnosis just hides the evidence. This page is educational; your vehicle needs its own inspection before any repair decision.
Dashboard warning lights
Red triangle master warning light on a Toyota or Lexus hybrid
The one everyone Googles. It's a pointer to a stored fault somewhere — not automatically a battery.
What it means →“Check Hybrid System” message on a Toyota or Lexus
A system-level message covering battery, inverter, motors, cooling and 12V — not a part number.
What it means →Check engine light on a Toyota or Lexus hybrid
On a hybrid this light covers two systems at once — the engine and the hybrid powertrain.
What it means →12V battery warning light on a Toyota or Lexus hybrid
The battery-shaped icon means the 12V system — the small, cheap battery, not the expensive one.
What it means →Diagnostic trouble codes
P0A80 — Replace Hybrid Battery Pack
The famous one. Its name says “replace hybrid battery pack” — that still isn't a diagnosis.
What it means →P0A7F — Hybrid Battery Pack Deterioration
Close relative of P0A80 — the ECU is reporting the pack has aged past its expected window.
What it means →P3000 — Battery Control System (Toyota / Lexus)
A pointer code. The sub-code (INF) stored alongside it is where the real information lives.
What it means →P3011 through P3024 — “Battery Block Becomes Weak”
One code per block inside the pack. Useful, specific — and still not an instruction to swap one module.
What it means →P0AA6 — Hybrid battery voltage system isolation fault
The one to take most seriously. It reports a loss of electrical isolation in the high-voltage system.
What it means →P0A0F — Engine failed to start
Reported by the hybrid system, but usually an engine-side problem — a useful reminder that not every P0A code is a battery.
What it means →P0A93 — Inverter cooling system performance
Points at the inverter's own coolant loop. Cheaper than a battery, and easy to misdiagnose as one.
What it means →C1259 — HV system regenerative malfunction
Stored by the brake control system, but it is usually pointing at the hybrid side. The classic misdiagnosis code.
What it means →P0AFA — Hybrid battery pack voltage low
Reports low pack voltage. Frequently a genuinely tired battery — but the sensing side has to be ruled out first.
What it means →P0A94 — DC/DC converter performance
A converter fault, not a battery fault — and on some model years it may still be covered. Check before you pay.
What it means →P1570 — Battery Module Individual Voltage Problem (Honda IMA)
Honda's IMA equivalent of a block-level code — specific modules inside the pack are reading wrong.
What it means →P1446 — Battery Module Individual Voltage Input Deviation (Honda IMA)
Honda's IMA imbalance code — the modules have drifted too far apart from each other.
What it means →P1449 — Battery Module Overheating or Deterioration (Honda IMA)
One Honda code with three published definitions — overheating, cell overheating, or deterioration.
What it means →P1575 — Motor Power Inverter Module Voltage Problem (Honda IMA)
Points at the inverter side, not the pack — worth knowing before anyone quotes you a battery.
What it means →P0A7D — Hybrid Battery Pack State of Charge Low
The pack's charge fell below the floor — very often a car that sat, not a car that's finished.
What it means →P1B96 — High Voltage Battery Performance Degradation (Hyundai / Kia)
Hyundai/Kia degradation code — but Kia grouped it with two sensor-circuit codes in a TSB.
What it means →P1B74 — High Voltage Battery Voltage Sensor Circuit (Hyundai / Kia)
The sensor-circuit member of the Hyundai/Kia trio — the cheapest of the three to be wrong about.
What it means →P1B70 — Battery Voltage Imbalance (Hyundai / Kia) or Cell Circuit Low (GM)
One code number, two different faults — which one you have depends on the badge.
What it means →P0A1F — Battery Energy Control Module Performance (Ford hybrids)
Ford's battery control module performance code — frequently a cooling story underneath.
What it means →P0A81 — Hybrid Battery Cooling Fan 1 Control Circuit / Open
Not a battery code. It's the code that becomes a battery code if you ignore it.
What it means →P0BBD — Hybrid Battery Voltage Variation (GM two-mode trucks)
The GM two-mode truck code — module voltages have spread further apart than allowed.
What it means →Got a code that isn't listed?
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