P0A0FEngine Failed to Start
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The control module commanded an engine start – by the hybrid system or an automatic start/stop restart – but the combustion engine did not reach a self-sustaining run within the allowed attempts. The code describes the result, not the cause. Toyota sets P0A0F with MIL on the 2010-2013 Prius and Prius v when a separated purge VSV/PCV hose leans out the mixture, often with P3190, P3191 and P0171. Kia traced P0A0F on the 2017-2018 Niro hybrid to an A/C pressure sensor harness chafed by an idler pulley, which disturbs the engine ECU 5 V reference. Audi sets P0A0F00 on 2019 A6/A7 3.0 mild hybrids after the second failed automatic restart, with a drive system warning. Look at fuel, air, ignition and engine sensor faults first.
- What you may notice
- Check engine light and hybrid or drive system warning
- Engine does not start, or runs briefly and stops
- Reduced power because the vehicle runs on the battery only
- Likely causes
- LikelyVacuum leak, e.g. separated purge VSV/PCV hose at the throttle body (Toyota Prius)
- PossibleShorted sensor harness pulling down the engine ECU 5 V reference (Kia Niro)
- PossibleFuel delivery or ignition fault preventing combustion
- RareFailed automatic restart of a mild hybrid with a cold engine (Audi A6/A7 2019)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.