P01A9
Alternative Fuel Rail/System Pressure - Too High
Alt fuel rail or system pressure above the expected operating range.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Common causes
Ordered by how often each turns out to be the cause.
- Regulator stuck closedCommon
Parts involved
- Alt Fuel Regulator
- Return Valve
P01A9 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.