P0191: Fuel Rail Pressure Sensor Circuit Range/Performance

P0191 means the fuel rail pressure sensor is providing readings outside the expected range for current engine operating conditions. The ECU relies on this sensor to precisely control fuel injection timing and quantity, so incorrect readings directly cause poor engine performance, rough running, and drivability issues.

P0191 is a fuel system-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0191 and illuminates the check engine light.

If your vehicle has triggered P0191, you may notice one or more of these symptoms:

• Check engine light on
• Engine hesitation or stumbling under acceleration
• Hard starting or extended cranking
• Rough idle or engine surging
• Reduced power output
• Possible stalling at idle

Here are the most common causes of P0191, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. You can drive to a workshop but expect rough running, reduced performance, and possible stalling. The ECU may use default fuel pressure values which reduces power and efficiency.

Follow these steps to pinpoint the root cause of P0191:

1. Use a scan tool to monitor live fuel rail pressure data. Compare the sensor reading to manufacturer specifications for idle (typically 3-5 bar for port injection, 50-120 bar for direct injection). Note if the reading is erratic, stuck, or clearly incorrect
2. With the engine off and ignition on, check the sensor reading. It should show atmospheric or residual rail pressure. A reading of 0 bar or maximum value suggests a sensor or wiring fault
3. Inspect the fuel rail pressure sensor connector for corrosion, bent pins, or moisture. Clean with electrical contact cleaner if needed
4. Check the sensor wiring for damage, chafing, or open circuits. Measure the reference voltage at the sensor connector (typically 5V) and the ground circuit
5. If the sensor and wiring appear fine, verify actual fuel pressure with a mechanical gauge to determine if the sensor is accurate or if there is a real fuel delivery problem
6. If fuel pressure is correct but the sensor reads wrong, replace the fuel rail pressure sensor

Repair costs for P0191 vary depending on the root cause and your vehicle. Here are typical estimates:

P0191 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0191 or indicate related issues: