Diesel injection pump fault.
P0251 — also written PO251, P 0251, 0251 — is the OBD-II code for injection pump fuel metering control 'a'. Same code, same fix: this page covers every spelling of it.
Injection pump 'A' fuel metering control (cam/rotor/injector) — the ECU can't hit the commanded fuel-rail pressure and blames the pump itself. On UK diesels this is almost always a worn high-pressure pump, a leaking pressure regulator (DRV/MPROP), or fuel contamination that's chewed the pump internals. Common on Bosch CP1/CP3/CP4 and Delphi/Denso common-rail systems.
P0251 is a fuel & air fault code, typically costing £250–£2000 to put right in a UK garage.
What P0251 actually feels like to drive
- Hard start when hot — cranks for 5+ seconds before catching
- Sudden power loss / limp mode uphill or under load
- Random cut-out at traffic lights then restarts fine
- Rail pressure gauge on scan tool won't hold commanded value
- Paired codes: P0087 (rail pressure too low), P0088 (too high), P1247/P1248 (regulator)
What causes P0251?
- Failed metering valve
- Wiring
- Pump worn
UK vehicles that throw P0251 most often
- Ford Transit 2.2/2.4 TDCi & Ranger 2.2/3.2 TDCi
- Vauxhall Vivaro / Renault Trafic / Nissan Primastar 2.0/1.6 dCi
- VW Crafter / Mercedes Sprinter OM651 2.1 CDI
- BMW 320d / 520d N47/B47 — MPROP/DRV valve stuck
- Peugeot Boxer / Citroën Relay / Fiat Ducato 2.2/2.3 HDi
- Land Rover Defender / Discovery 2.7/3.0 TDV6
How P0251 is fixed
- Metering valve replacement
- Pump rebuild
The P0251 misdiagnosis that wastes money
Everyone jumps to a £1,200 HP pump. Do these first. One — pull the fuel filter, cut it open, look for metal glitter or milky water. If the filter is contaminated the pump is already damaged and the injectors need testing before any new pump goes on, otherwise you'll kill the new one in a fortnight. Two — read live rail-pressure vs commanded rail-pressure at idle and on a snap-throttle. If commanded says 300 bar and actual reads 280 bar and drifts, it's usually the pressure regulator (£85–£180) not the whole pump. Three — leak-off test the injectors. A single leaking injector dumps rail pressure and the pump gets the blame. Never fit a pump without an injector leak-off report on paper.
What a UK garage should charge for P0251
Diagnostic + live rail-pressure trace + leak-off test £80–£140, fuel filter + fresh filter housing prime £55–£120, DRV/MPROP fuel-pressure regulator £150–£320 fitted, single injector recon/replace £180–£420 each, high-pressure fuel pump replacement £850–£1,800 independent (main dealer £1,600–£3,200). Labour From £70/hr.
P0251 repair cost in the UK
Most P0251 repairs land between £250–£2000 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 P0251
On BMW N47/B47 the MPROP (fuel quantity valve) is £110 and takes 40 minutes — 8 times out of 10 it fixes P0251 without touching the pump. On Ford Transit 2.2 TDCi the fuel filter housing check-valve fails and lets rail pressure bleed back overnight — new filter housing £95, sorted. On any CP4 pump (later VW/Audi/Ford/JLR) if you've had bad fuel do not just fit a pump — the whole fuel system needs flushing including tank drop, or you'll write off the new pump within weeks. <a href="/ask-a-mechanic-uk?code=P0251">Ask Bob about your P0251</a> for £14.99 with make, model, mileage, and any paired P0087/P0088 codes — you'll get the right test order before you spend £1,000+ on a pump you might not need.
Can you drive with P0251?
Limp-mode possible.
Urgency: high.