OBD-II Code
P0A1A
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$1,800–$5,500
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$1,800 (warranty-covered inverter swap) to $5,500 (out-of-warranty inverter replacement).
P0A1A is set when the generator control module (MG1 on Toyota HSD, the generator-side power electronics on Ford eCVT, or the equivalent inverter sub-section on series-hybrid platforms like Volt Gen 1 extended-range mode) fails its internal self-test, loses communication with the hybrid ECU, or reports an internal fault that does not map to a more specific code.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0A1A is set when the generator control module (MG1 on Toyota HSD, the generator-side power electronics on Ford eCVT, or the equivalent inverter sub-…
P0A1A is set when the generator control module (MG1 on Toyota HSD, the generator-side power electronics on Ford eCVT, or the equivalent inverter sub-section on series-hybrid platforms like Volt Gen 1 extended-range mode) fails its internal self-test, loses communication with the hybrid ECU, or reports an internal fault that does not map to a more specific code. On Toyota HSD, MG1 is the smaller of the two motor-generators and is responsible for engine starting, generator function during charge events, and reaction-torque control during planetary-gear-set operation; a P0A1A puts the hybrid system in failsafe and typically prevents READY mode entry.
Cheapest-first ladder
- scan-tool the inverter CAN bus (Toyota uses a dedicated HV-CAN at 500 kbps separate from the chassis bus) for communication health; confirm 12V supply to the inverter wake circuit at key-on; inspect the inverter low-voltage harness connector for corrosion or backed-out pins.
- If communication is healthy, the fault is internal to the generator control module and the only path is replacement of the inverter assembly or, on platforms that support it, the discrete MG1 controller sub-board.
- Verify HV pack voltage with an isolation tester before opening any inverter cover (Prius Gen 2 pack reads 201V nominal, Gen 3 reads 207V, Volt Gen 1 reads 360V, Volt Gen 2 reads 355V, Leaf Gen 1 reads 364V, Tesla packs read 350-400V depending on platform).
- DO NOT probe HV orange-wire circuits with a standard multimeter.
- Always service HV with Class 0 1000V gloves, isolation tester (Megger), and DC-rated lugged probes; the HV interlock loop exists specifically to drop pack contactors when the service plug is removed and must NEVER be bypassed at lethal risk.
Vehicle-specific patterns2004-2009 Toyota Prius Gen 2 throws P0A1A as part of the well-known inverter failure cluster that triggered Toyota's extended warranty on the inverte…
- 2004-2009Toyota Prius Gen 2 throws P0A1A as part of the well-known inverter failure cluster that triggered Toyota's extended warranty on the inverter assembly to 10 years / 150,000 miles in many markets; the warranty also covers the inverter coolant pump-related cascade failures and many Gen 2 P0A1A claims close under that program.
- 2010-2015Prius Gen 3 throws P0A1A less frequently but when it does, the inverter is the part.
- 2007-2017Camry Hybrid and 2011-2017 Highlander Hybrid share the architecture and throw the code with the same root cause.
- 2011-2019GM Volt Gen 1/Gen 2 throws P0A1A from Voltec drive unit isolation faults that propagate to the MG-A (generator) controller; GM has service info covering the isolation test procedure.
- 2011-2017Nissan Leaf Gen 1 uses a single motor (no MG1 equivalent) and typically does not throw P0A1A.
- 2003-2015Honda Civic Hybrid (IMA) throws a similar generator-side fault when the IMA motor controller fails; Honda's IMA battery extended warranty often touches adjacent repairs.
Estimated repair$1,800 (warranty-covered inverter swap) to $5,500 (out-of-warranty inverter replacement).
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