OBD-II Code

P0A0F

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)

$180–$4,200

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P0A0F is set when the hybrid control module commands an engine start sequence but the engine fails to crank or fails to achieve self-sustaining combustion within the calibrated window (typically 2-3 seconds on Toyota HSD, 1.5 seconds on Ford eCVT).

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 procedureP0A0F is set when the hybrid control module commands an engine start sequence but the engine fails to crank or fails to achieve self-sustaining combu…+

The cheapest-first ladder starts with a scan-tool live-data check

confirm MG1 RPM during the start attempt (should ramp to 900-1100 RPM on Prius Gen 2/3; below 500 RPM points to MG1 resolver or inverter), then verify HV battery voltage stays above 180V on Gen 2 NHW20 or 200V on Gen 3 ZVW30 during cranking (sag below those thresholds means a weak module pulling the pack down).
Next, pull the engine-side codes — P0A0F rarely lives alone, and a companion P0335 (crank sensor), P0340 (cam sensor), P0171 (lean), or P0420 will tell you whether the failure is electrical-spin or fuel/spark/compression.
Caveat: on Prius Gen 2 with 150K+ miles, a tired HV battery can throw P0A0F intermittently on cold mornings without setting P0A80 — the pack has enough voltage at rest to pass isolation but sags under MG1 cranking load.

Vehicle-specific patterns2004-2009 Toyota Prius Gen 2 (NHW20) — weak HV battery module (one of 28 NiMH sticks) sags during MG1 cranking; check Techstream block voltages, any…+

2004-2009Toyota Prius Gen 2 (NHW20) — weak HV battery module (one of 28 NiMH sticks) sags during MG1 cranking; check Techstream block voltages, any block reading 0.3V below the pack average under load is the culprit.
2010-2015Toyota Prius Gen 3 (ZVW30) — inverter MG1 IGBT failure causes failed-start with companion P0A94/P0A1A; TSB T-SB-0090-14 covers inverter assembly replacement.
2013-2018Ford Fusion Hybrid / C-Max — BECM software calibration bug throws P0A0F after deep discharge from extended sit; Ford TSB 18-2079 reflashes BECM.
2011-2015Chevrolet Volt — 12V auxiliary battery weak (below 11.8V resting) prevents HPCM2 wake-up and aborts engine-start request.

Estimated repair$180 to $4,200.

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