P0A0F: Engine Failed to Start
What to do
This is a conventional engine problem rather than a hybrid one — fuel, spark or compression — and there is no starter motor to blame, because the car does not have one. If the vehicle has been feeling slow or the hybrid battery keeps running low, that is the same fault: the engine is not running to recharge it. Have it looked at before the pack is fully depleted, since the car will stop entirely at that point.
What this code means
The hybrid system tried to start the petrol engine and it did not run. The useful thing about this code is what it rules out.
A hybrid has no starter motor. The engine is spun up by one of the motor-generators, which can turn it far faster and more smoothly than a conventional starter ever did — which is why a hybrid engine seems to appear rather than crank. So this code is never a starter fault, never a starter solenoid, and never a flat battery in the ordinary sense. The cranking half worked; the module confirmed the engine turned and did not fire.
That points the diagnosis firmly at the engine as an engine: fuel delivery, spark, compression, or a sensor the engine module needs. All the ordinary reasons a petrol engine will not run apply unchanged, and none of them is hybrid-specific.
Why it is often noticed late. The car can usually still move on electric power alone, so the first symptom is not a breakdown — it is a hybrid battery that keeps running down because nothing is recharging it, a car that feels unusually slow, and eventually a refusal to move at all once the pack is depleted. Anyone reporting "the battery keeps going flat" on a hybrid may be describing an engine that has quietly stopped starting.
Likely causes
Start here
- Faulty crankshaft position sensor · moderate
- Low fuel pressure · moderate
- Faulty ignition coil · easy
- Worn or fouled spark plugs · easy
Less common
- Low engine compression · specialist
- Failed fuel pump · moderate
Rare
- Faulty motor generator · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0A0F.