OBD-II trouble code
P0363: Misfire Detected - Fueling Disabled
This code describes what the engine computer did, not what went wrong. It found a misfire bad enough to threaten the catalytic converter and shut the injector off to protect it — so the dead cylinder you are about to test is dead on purpose.
Quick facts
- System
- Powertrain
- Category
- Ignition / Misfire
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $60 – $3,500
- DIY difficulty
- Intermediate DIY
What does P0363 mean?
Almost every fault code names a condition. This one names a decision. The engine control module detected misfiring severe enough to put the exhaust system at risk and responded by commanding the injector on the affected cylinder to stop opening. The code is the record of that intervention.
The reasoning behind the strategy is worth following, because it explains why the module is prepared to take such a drastic step. When a cylinder fails to burn its charge, the fuel does not vanish — it is pumped out into the exhaust largely intact. The catalytic converter is an oxidising device running at several hundred degrees, and raw fuel arriving in it does exactly what raw fuel does in the presence of oxygen and heat: it burns, inside the converter, where nothing is designed to cope with the temperature. Substrate melts, the honeycomb collapses, and a component costing many times more than the ignition part that started the problem is destroyed in a few minutes of driving. Cutting the fuel to that one cylinder stops the supply of unburnt fuel at source. The cylinder still pumps air, the engine still runs, and the converter is spared.
The practical consequence for anyone diagnosing this is that ordinary reflexes give false answers. A technician who finds no injector pulse on that cylinder, or no fuel contribution in a cylinder balance test, has confirmed only that the strategy is working. Neither is evidence of an injector fault. The correct sequence is to clear the codes, let the module restore fuel to the cylinder, and then repeat any fuel-side test while the engine is running normally — accepting that the misfire will return, so the test needs to be quick and the engine should not be driven hard in the meantime. Tests that do not depend on fuelling are unaffected and can be done straight away: compression, cylinder leakage, spark output, coil resistance, and the physical condition of the plug and boot.
The other thing this code does not do is name a cylinder. On its own it tells you a cylinder was shut down and nothing more, so read every stored code before touching anything. A cylinder-specific misfire code, an ignition coil code or an injector circuit code stored alongside it is the piece of information you actually need, and freeze frame data will tell you the load and engine speed at which the misfire became bad enough to trigger the cut.
One subtlety worth carrying: a cylinder running on air alone leans out the exhaust stream reaching that bank's oxygen sensor. Most strategies suspend fuel trim learning while a misfire is active for exactly this reason, but any lean-related code stored alongside this one should still be treated as a possible consequence of the shutdown rather than as an independent second fault until the misfire itself is resolved.
Common causes
- Failed ignition coil on the affected cylinder, which is the most common single cause of a misfire severe enough to trigger the cut
- Worn, fouled, cracked or incorrectly gapped spark plug
- Split, tracked or oil-soaked coil boot letting the spark escape to the head
- Failed or badly restricted fuel injector on that cylinder
- Loss of compression from a burnt valve, a failed head gasket or worn rings
- Vacuum leak drawn into one cylinder through a cracked intake gasket or split hose
- Damaged wiring or connector in the coil or injector circuit for that cylinder
- Carbon build-up on an intake valve on a direct injection engine, disrupting the charge on that cylinder alone
Symptoms
- Rough idle and obvious shaking, especially on an engine with few cylinders
- Marked loss of power and poor acceleration with one cylinder contributing nothing
- Check engine light on and frequently flashing
- Engine running noticeably unevenly, sometimes described as running on one cylinder fewer
- Poor fuel economy
- Cylinder-specific misfire codes stored alongside this one
Diagnostic steps
- 1.Read every stored code and the freeze frame data first. This code identifies no cylinder by itself, and the companion codes usually do.
- 2.Note the engine load, engine speed and coolant temperature captured when the code set. A misfire that only becomes severe under load points somewhere different from one present at idle.
- 3.Do the tests that do not depend on fuelling straight away: spark output, coil resistance, plug condition, boot condition, compression and cylinder leakage. None of these are affected by the injector being switched off.
- 4.Do not treat a silent injector or a zero fuel contribution on the affected cylinder as a fault. That is the protection strategy working exactly as designed.
- 5.To test the fuel side properly, clear the codes so the module restores fuelling, then perform the test promptly. Expect the misfire to return, and do not drive the vehicle hard in that window.
- 6.Swap the suspect coil with one from a neighbouring cylinder and see whether the misfire follows it. This remains the cheapest decisive test in the book on a coil-per-cylinder engine.
- 7.If compression on the affected cylinder is low, stop chasing electrical causes. Add a small amount of oil and retest to separate ring wear from a valve or head gasket problem.
- 8.Inspect the intake for a vacuum leak feeding one cylinder, and on a direct injection engine consider carbon build-up on the intake valves if the ignition and fuel components all check out.
Repair cost
$60 – $3,500
The spread here is wider than on almost any other code because the code describes a response rather than a cause. A spark plug and boot is $60 to $200. An ignition coil is typically $150 to $400 fitted. An injector runs $200 to $600 on most engines and considerably more where the rail sits under an intake manifold. Compression loss is the expensive end: a head gasket is $1,200 to $2,500 and valve or ring work reaches $3,500 and beyond. Add the catalytic converter, at $600 to $2,500, if the misfire ran for long enough before the fuel cut took effect.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with ignition coil replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.