Same fault as P2177 but on the second cylinder bank of a V engine.
P2179 — also written P2179, P 2179, 2179 — is the OBD-II code for system too lean off idle (bank 2). Same code, same fix: this page covers every spelling of it.
P2179 is a fuel & air fault code, typically costing £80–£700 to put right in a UK garage.
What causes P2179?
- Vacuum or boost leak on bank 2
- Injector restriction on bank 2
- Fuel supply weakness affecting both banks
- MAF under-reading
How P2179 is fixed
- Compare bank 1 and bank 2 fuel trims
- Smoke-test bank 2 intake
- Test fuel pressure and injector flow
P2179 repair cost in the UK
Most P2179 repairs land between £80–£700 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 P2179?
Yes short-term with gentle driving.
Urgency: medium.
What P2179 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 P2179 specifically — system too lean off idle (bank 2) — 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 P2179 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P2179 that means working through them like this:
- Vacuum or boost leak on bank 2 — found with a smoke test rather than by eye, because the leak that throws the code is usually too small to hear.
- Injector restriction on bank 2 — measured as a pressure or flow difference across the component, so a partial restriction is not mistaken for a clear one.
- Fuel supply weakness affecting both banks — confirmed with live data before any part is bought.
- MAF under-reading — confirmed with live data before any part is bought.
An hour of diagnostic time on P2179 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 P2179
- Compare bank 1 and bank 2 fuel trims
- Smoke-test bank 2 intake
- Test fuel pressure and injector flow
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 P2179 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, P2179 typically lands at £80–£700 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P2179 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 P2179 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.