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.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Symptoms
- 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
Most likely causes
- Vacuum leak, e.g. separated purge VSV/PCV hose at the throttle body (Toyota Prius)
- Shorted sensor harness pulling down the engine ECU 5 V reference (Kia Niro)
- Fuel delivery or ignition fault preventing combustion
- Failed automatic restart of a mild hybrid with a cold engine (Audi A6/A7 2019)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It can trigger limp mode.
- It affects emissions.
What each character of P0A0F means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- A: Hybrid or air and fuel
- 0F: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0A0F?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P0A0F?
The most common causes are: vacuum leak, e.g. separated purge VSV/PCV hose at the throttle body (Toyota Prius); shorted sensor harness pulling down the engine ECU 5 V reference (Kia Niro); fuel delivery or ignition fault preventing combustion.
Related codes
- P0A1DHybrid/EV Powertrain Control Module A
- P0335Crankshaft Position Sensor A Circuit
- P0171System Too Lean Bank 1
- P0404EGR A Control Circuit Range/Performance
Sources
- static.nhtsa.gov: MC 10111294 9999
- static.nhtsa.gov: MC 10136620 9999
- static.nhtsa.gov: MC 10168576 0001
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.