P0191 on Mazda: How to Diagnose & Fix
Fuel Rail Pressure Sensor Circuit Range/Performance
1 Mazda model · 1 documented issue · 1 critical
P0191 on Mazda by model: symptoms, diagnosis and fix
The in-tank low-pressure fuel pump supplied by Denso used an impeller molded with too low a density; it absorbs fuel, swells, cracks and deforms, then binds against the pump housing. Fuel delivery drops off, the engine runs lean, hesitates and can stall outright - sometimes at speed - and often will not restart when hot. This is the same defective Denso pump batch that hit millions of vehicles across several brands. Mazda's campaign covering 2018 Mazda3 and other models is NHTSA 21V875000, roughly 121,000 vehicles, with owner letters mailed July 2022. Owners report a long crank, a rough idle and low fuel rail pressure codes before the pump quits entirely.
Common Symptoms
- Engine stalls while driving
- Extended cranking or no-start, especially when hot
- Rough idle and hesitation under load
- Whining or silence from the fuel tank at key-on
- Check engine light for low fuel rail pressure
How to Fix
Check the VIN against recall 21V875000; covered vehicles get the in-tank low-pressure fuel pump module replaced free of charge at a Mazda dealer. Outside coverage, diagnose with a fuel pressure reading at the low-pressure side rather than replacing the high-pressure pump or injectors on a guess - a cracked impeller shows up as low or erratic supply pressure. Replace the pump module with the updated Denso part number, not the original superseded unit.
Sources for this issue (3)
P0191 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0191 mean on a Mazda?
P0191 stands for "Fuel Rail Pressure Sensor Circuit Range/Performance." This code sets when the fuel rail pressure sensor's signal is out of its expected range or doesn't match what the computer expects for current conditions. On direct-injection and many modern engines, this sensor reports fuel pressure in the rail so the computer can precisely control fueling and the fuel pump. When the reading is implausible — too steady, erratic, or inconsistent with commanded pressure — this code is set, sometimes with hard starting, hesitation, or reduced power. It generally points to the sensor or its wiring, though an actual fuel-pressure problem can also trigger it. On Mazda it is documented across 1 model: Mazda3.
What are the most common causes of P0191?
The most common causes of P0191 are: Faulty fuel rail pressure sensor, Corroded, loose, or damaged sensor connector, Open, shorted, or high-resistance sensor wiring, Actual fuel pressure out of range (weak pump or regulator), Restricted fuel filter or supply line, Loss of reference voltage or ground from the ECM/PCM, Faulty fuel pressure regulator or control valve. The specific cause varies by vehicle.
How much does it cost to fix P0191 on a Mazda?
Repair costs vary widely with the root cause and Mazda model; each issue on this page carries its own estimate where one is published.
Looking for P0191 on a different make?
View P0191 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.