The engine goes lean specifically when you ask for power. Fuel supply that cannot keep up is the classic cause.
P2191 — also written P2191, P 2191, 2191 — is the OBD-II code for system too lean at higher load (bank 1). Same code, same fix: this page covers every spelling of it.
P2191 is a fuel & air fault code, typically costing £80–£800 to put right in a UK garage.
What causes P2191?
- Blocked fuel filter
- Weak fuel pump
- Restricted injectors
- Boost leak opening under pressure
- MAF under-reading at high flow
How P2191 is fixed
- Test fuel pressure at full load, not idle
- Change the fuel filter
- Smoke-test the charge pipework
- Injector clean or flow test
P2191 repair cost in the UK
Most P2191 repairs land between £80–£800 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.
Can you drive with P2191?
Drive gently. Sustained lean running under boost can damage pistons.
Urgency: medium.
What P2191 is telling you
Fuel and air codes come from the ECU comparing the fuelling it commanded against the pressure, flow or mixture it actually measured. When those numbers disagree beyond the allowed tolerance, the ECU backs off to a safe map and logs the code.
On P2191 specifically — system too lean at higher load (bank 1) — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P2191 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P2191 that means working through them like this:
- Blocked fuel filter — measured as a pressure or flow difference across the component, so a partial restriction is not mistaken for a clear one.
- Weak fuel pump — tested for delivery and current draw under load, not just for whether it runs.
- Restricted injectors — measured as a pressure or flow difference across the component, so a partial restriction is not mistaken for a clear one.
- Boost leak opening under pressure — found with a smoke test rather than by eye, because the leak that throws the code is usually too small to hear.
- MAF under-reading at high flow — confirmed with live data before any part is bought.
An hour of diagnostic time on P2191 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P2191
- Test fuel pressure at full load, not idle
- Change the fuel filter
- Smoke-test the charge pipework
- Injector clean or flow test
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P2191 is ignored
The car will usually keep going, but the fault will not clear itself and the related monitors stay incomplete — which matters if an MOT is due, because a car that has not finished its emissions self-tests can be refused.
For reference, P2191 typically lands at £80–£800 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P2191 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P2191 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.