P0313
PowertrainMisfire Detected with Low Fuel
The ECU watches the crankshaft speed for the tiny stumbles a misfire creates, and when it sees those stumbles while the fuel level sender is reading low (usually under about 15% in the tank), it sets P0313 instead of a plain misfire code. It's basically the car telling you it lost combustion in one or more cylinders at the exact moment you were running on fumes. Most of the time it's a near-empty tank uncovering the fuel pump pickup, but it can also point to a tired pump or a genuine ignition fault that only shows up when fuel delivery is already marginal. Get fuel in it first before you start throwing parts at it.
ⓘ Information only. This page provides general educational information about fault code P0313. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0313 mean?
P0313 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Misfire Detected with Low Fuel.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, sometimes flashing if the misfire is bad enough to risk the cat
- • Rough, lumpy idle with the whole car shuddering, worst when the tank is almost empty
- • Hesitation or a flat spot when you put your foot down
- • Engine cutting out or threatening to stall at junctions and in slow traffic
- • Hard starting, or on the worst cases a no-start until you put some fuel in
- • Fuel economy looking worse than usual on the trip computer
Possible causes
Causes commonly associated with P0313, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Tank run too low, uncovering the fuel pump pickup so it sucks air and pressure drops. This is the single most common reason this exact code fires rather than a normal misfire code
- 2. Weak or failing in-tank fuel pump that just about copes with a full tank but gives up when the level drops and the pickup is working harder
- 3. Clogged fuel filter starving the rail, more of an issue on older cars and diesels with a serviceable inline filter
- 4. Worn or fouled spark plugs giving a weak spark that only fails under the leaner conditions a low tank creates
- 5. Failing ignition coil pack dropping out a cylinder, common on the VAG 1.4/1.6 petrols and plenty of older Fords
- 6. Blocked or leaking injector delivering the wrong amount of fuel to one cylinder
- 7. Vacuum leak on the intake leaning out the mixture, often a perished hose or a split on the manifold gasket
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Put fuel in the tank above a quarter, clear the code, and drive it. If P0313 stays away with a decent amount of fuel on board, you've found your answer and it costs you nothing
- 2. Read the fuel level PID on the scan tool and compare it to the dash gauge. A sender reading low when the tank actually has fuel in it will trip this code on its own and needs sorting
- 3. Pull every stored and pending code. A P0300 series misfire or a P0171/P0174 lean code alongside this one tells you which cylinders and which direction to look
- 4. Hook up a fuel pressure gauge at the rail and watch it at idle then under load. Most petrol systems want somewhere in the 30-65 psi range, and a pressure that sags off when you load the engine points at the pump or filter
- 5. Pull the plugs and check them. Look for one that's oil-fouled, worn, or sooty compared to the rest, and inspect the coils for cracks or tracking while they're out
- 6. Smoke test the intake for vacuum leaks if the fuel side checks out clean, paying attention to the manifold gasket and any cracked hoses
Common questions about P0313
If it turns out to be the fuel pump, is a cheap aftermarket one worth fitting? +
For a mainstream car, a decent brand-name aftermarket pump like Bosch, Pierburg or Walbro does the same job as the dealer part for a good bit less, and plenty of garages fit them every day. Where I'd be careful is the unbranded eBay kits at £40 with no maker on the box. They often run the wrong pressure or die inside a year, and the in-tank pump is not a part you want to be doing twice because of the labour to drop the tank or lift the seat. Spend the extra and buy a recognised brand.
Can I keep driving while this code is up? +
If you've just refilled and the light's about to clear itself, you're fine to carry on. If it's still misfiring with fuel in the tank, ease off. A persistent misfire pumps raw fuel into the exhaust and that cooks the catalytic converter, turning a cheap fix into a £400-plus one. A flashing engine light means stop driving like that now, because the cat is being damaged as you go. Steady misfire, get it looked at within a few days.
Will this stop my car passing the MOT? +
The code by itself isn't on the tester's checklist, but an engine management light glowing on the dash at the time of test is a fail under the current rules. If the cause was just a near-empty tank, fill up, clear the code and run it through a few drive cycles so the light goes out and the readiness monitors set before you book it in. If it's a real misfire, the emissions side of the test will likely fail too because the unburned fuel skews the readings.
What sort of money am I looking at to fix it? +
Depends entirely on what's actually wrong. If it's just low fuel, it costs you a tank of petrol. A set of plugs runs maybe £40-£120 fitted at an independent, a single ignition coil similar. A fuel filter is cheap on most cars. A new in-tank fuel pump is where it gets dearer, figure £150-£400 fitted at a good independent and noticeably more at a main dealer where labour rates and genuine parts push it toward £500-£800. Chasing a wiring fault or an injector problem sits somewhere in the middle and depends on how long it takes to find.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →