Rail pressure not matching commanded.
P0191 — also written PO191, P 0191, 0191 — is the OBD-II code for fuel rail pressure sensor range/performance. Same code, same fix: this page covers every spelling of it.
The ECU is confused because the fuel pressure it’s seeing doesn't match what it asked for. On the UK roads, we see this constantly on high-mileage common rail diesels like the Ford TDCI and Vauxhall CDTi units.
P0191 is a fuel & air fault code, typically costing £200–£1800 to put right in a UK garage.
What P0191 actually feels like to drive
- The car feels like it's 'hunting' or surging while you're idling at the lights.
- It cut out completely when you put your foot down to overtake on an A-road.
- Takes way too many cranks to fire up when the engine is stone cold.
- The 'Limp Home' mode kicks in and you can't get over 3000 revs.
- A noticeable 'diesel knock' sound that gets louder under load.
What causes P0191?
- Sensor fault
- Failing high-pressure pump
- Leaking injector
UK vehicles that throw P0191 most often
- Ford Focus/Mondeo 2.0 TDCi (DW10) 2012-2018
- Vauxhall Insignia 2.0 CDTi (A20DTH) 2008-2015
- Nissan Qashqai 1.5 dCi (K9K) 2010-2017
- BMW 320d (N47) 2007-2013
- Land Rover Freelander 2 2.2 SD4 2010-2015
How P0191 is fixed
- Sensor replacement
- HP pump test
- Injector test
The P0191 misdiagnosis that wastes money
I see it all the time—folks jump straight to the high-pressure pump because they’ve been reading horror stories online. They spend £800 on a reconditioned Bosch pump only for the light to come back on at the end of the road. Most of the time, P0191 is just a tired sensor or a dodgy bit of wiring in the loom. I’ve even seen people bin perfectly good injectors when it was actually just a clogged fuel filter that hadn’t been changed since the Blair administration. Always check the basics first.
What a UK garage should charge for P0191
Expect to pay £60-£90 for a proper diagnostic plug-in. If it’s just the rail sensor, a genuine Bosch or Delphi part is usually £120-£180, plus an hour's labour. However, if the high-pressure pump has "shelled" its internals, you're looking at £800-£1,200 for a Bosch exchange unit plus a few hundred more for labour. A single refurbished injector will set you back about £150-£200 plus fitting. Main dealers will easily double these prices for the exact same parts.
P0191 repair cost in the UK
Most P0191 repairs land between £200–£1800 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0191
Before you let a garage swap any parts, ask them for a 'leak-off test' on the injectors. It’s a simple 20-minute job with a set of vials that shows if one injector is bleeding off too much pressure. If they don't know what that is, find another garage. Also, insist they check the sensor plug for 'fretting corrosion'—it’s a tiny bit of green crust on the pins that plays havoc with the voltage. A squirt of contact cleaner is a lot cheaper than a £400 rail sensor.
Can you drive with P0191?
Drivable, expect poor performance.
Urgency: medium.