OBD-II trouble code
P0263: Cylinder 1 Contribution/Balance Fault
The engine computer measured how hard each cylinder pushes the crankshaft and found cylinder 1 pulling less than its share. This is a weak-cylinder code, not a wiring code — the cause can be fuel, spark, or compression.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $3,000
- DIY difficulty
- Intermediate DIY
What does P0263 mean?
P0263 is a fundamentally different kind of code from the injector circuit codes that surround it. P0261 and P0262 are electrical — the engine control module (ECM) looked at the wire going to the cylinder 1 injector and did not like the voltage. P0263 says nothing about wiring at all. It says the ECM measured the actual work cylinder 1 is doing and found it lacking.
The measurement comes from the crankshaft position sensor. Every power stroke gives the crankshaft a small, brief acceleration, and the ECM can see that acceleration in the sensor signal as a tiny variation in rotational speed. On a healthy engine, each cylinder produces a push of roughly equal strength. The ECM continuously compares the pushes and calculates a contribution value for each cylinder. When cylinder 1's contribution falls outside the allowed spread relative to the others, P0263 sets.
That is why the code is a symptom rather than a diagnosis. Cylinder 1 can under-contribute because it is not getting enough fuel (a clogged, weak, or slow-opening injector), because it is not igniting the fuel well (a worn plug, a failing coil, a bad plug wire), or because it cannot hold the combustion pressure it makes (worn rings, a burnt or leaking valve, a head gasket leaking between cylinders). Any of the three shows up identically to the crankshaft sensor.
On diesel applications — the Ford Power Stroke family in particular — contribution/balance codes are a routine, well-understood diagnostic and are almost always injector-related, because a diesel has no ignition system to blame. On gasoline engines the code is less common and the ignition and compression paths deserve equal weight. Either way, the honest sequence is to find out which of the three systems is short before spending money.
Common causes
- Clogged, restricted, or weak cylinder 1 fuel injector delivering less fuel than commanded
- Slow-responding or internally worn injector (common on high-mileage diesels)
- Worn spark plug, failing ignition coil, or bad plug wire on cylinder 1 (gasoline engines)
- Low compression on cylinder 1 from worn rings, a burnt or leaking valve, or a bent valve
- Head gasket leaking between cylinder 1 and an adjacent cylinder or into the cooling system
- Intake manifold gasket or vacuum leak feeding only the cylinder 1 runner
- Low fuel pressure or a restricted fuel filter starving the cylinder under load
- Damaged wiring or a poor connection at the cylinder 1 injector reducing pulse quality
Symptoms
- Check engine light on
- Rough idle and a noticeable shake, worst at low RPM
- Loss of power and hesitation under acceleration
- Misfire codes such as P0301 or P0300 alongside P0263
- Poor fuel economy
- Hard starting or extended cranking, especially on diesels
- Black or excessive exhaust smoke on diesel applications
Diagnostic steps
- 1.Record all stored codes first. If P0261, P0262, or P0201 are present with P0263, the injector circuit is electrically faulty and that is where to start — the balance code is downstream of it.
- 2.Run the scan tool's cylinder balance or injector contribution test and note how far cylinder 1 deviates from the others. A large, consistent deviation is meaningful; a small, wandering one often is not.
- 3.Locate cylinder 1 for your specific engine before touching anything. On an inline engine it is usually at the front; on a V engine it is on Bank 1 but the physical position varies by manufacturer.
- 4.On a gasoline engine, pull the cylinder 1 spark plug and inspect it against the others. A fouled, worn, or oil-soaked plug explains the weak contribution without any injector work.
- 5.Swap the cylinder 1 ignition coil with a neighboring cylinder, clear the codes, and drive. If the fault moves to the other cylinder, the coil is the problem.
- 6.Perform a relative compression test (or a conventional compression and leak-down test) on cylinder 1. This separates a mechanical problem from a fuel or spark problem definitively, and doing it early prevents buying an injector for a worn cylinder.
- 7.Check fuel pressure at the rail under load and inspect the fuel filter. A system-wide fuel supply problem can present as a single weak cylinder.
- 8.Listen to the cylinder 1 injector with a stethoscope or run an injector buzz test to confirm it is clicking and responding.
- 9.If fuel, spark, and compression all check out, swap the cylinder 1 injector with one from another cylinder and see whether the code follows the injector — the cleanest test available on this code.
Repair cost
$100 – $3,000
A spark plug or ignition coil on the weak cylinder is often $100-$350 installed. A single fuel injector runs $60-$400 in parts plus 0.5-3 hours labor; diesel injectors are considerably more, frequently $400-$900 each installed. A fuel filter or fuel pressure repair typically lands at $150-$800. If the cause is mechanical — worn rings, a burnt valve, or a head gasket — repairs start around $1,200 and can exceed $3,000. Diagnosis alone is usually $100-$200 because this code requires testing rather than a single measurement.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with fuel injector 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.