P0263: Cylinder 1 Contribution/Balance
Do not keep driving
Expect rough running and reduced power. Ask for a compression or leak-down test if the injector tests good — this code measures the result, not the cause, and replacing an injector on the strength of it alone is a common wasted repair.
What this code means
Cylinder 1 is contributing measurably less than its neighbours. This is a different class of finding from the circuit codes: nothing electrical is wrong, but the module has measured crankshaft acceleration cylinder by cylinder and concluded this one is not pulling its weight. Because it measures outcome rather than cause, the suspect list is wide — a partially blocked injector, worn rings, a leaking valve, or low compression all reduce contribution identically.
The balance code is worth reading alongside its siblings. A contribution fault with no injector circuit code and no misfire suggests a mechanical weakness rather than a fuelling one, and that points at a compression and leak-down test rather than at parts.
Likely causes
Start here
- Clogged fuel injectors · moderate
- Low engine compression · specialist
- Burnt or leaking valve · specialist
- Failed fuel injector · moderate
Less common
- Worn piston rings · specialist
- Carbon deposits on intake valves · specialist
- Collapsed or stuck valve lifter · specialist
Rare
- Head gasket failure · specialist
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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