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FuelSeverity Medium: diagnose soon

P0191Fuel Rail Pressure Sensor "A" Circuit Range/Performance

What it means

The fuel rail pressure sensor signal is electrically possible, but it doesn't make sense compared with other sensors or with what the engine is doing. The fuel rail pressure sensor measures the fuel pressure in the rail.

Symptoms

  • No start or long cranking
  • Limp mode with low power
  • Stalling or rough running

Common causes

  • Faulty or drifting rail pressure sensor
  • Real pressure problem (supply, regulator, pump)
  • Poor ground or connection on the sensor

What to check first

  1. Key on, engine off: the sensor should read close to zero pressure (about 0.5 V)
  2. Compare requested and actual pressure while cranking and at idle
  3. Check the sensor 5 V reference and ground
Can I drive with P0191? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0191

Diesel rail pressure sensorWiring, typical values, multimeter and scope tests

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P0191: questions and answers

What does P0191 mean?

P0191: Fuel Rail Pressure Sensor "A" Circuit Range/Performance. The fuel rail pressure sensor signal is electrically possible, but it doesn't make sense compared with other sensors or with what the engine is doing. The fuel rail pressure sensor measures the fuel pressure in the rail.

What are the symptoms of P0191?

No start or long cranking. Limp mode with low power. Stalling or rough running.

What causes P0191?

Faulty or drifting rail pressure sensor. Real pressure problem (supply, regulator, pump). Poor ground or connection on the sensor.

How do you diagnose P0191?

1. Key on, engine off: the sensor should read close to zero pressure (about 0.5 V) 2. Compare requested and actual pressure while cranking and at idle 3. Check the sensor 5 V reference and ground

Can I drive with P0191?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.