P0263
Cylinder 1 Contribution/Balance
Fuel injector / cylinder balance
Generic OBD-II
High
What it means
P0263 means the ECM has determined that cylinder 1 is producing less power than the other cylinders — its "contribution" to running the engine is out of balance. This usually points to a weak or clogged injector, low fuel delivery, or low compression on cylinder 1, and it shows up as rough running, misfire, and reduced power.
High
Can I keep driving? Limited — cylinder 1 is contributing less than the others, so the engine runs rough and down on power; drive gently until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle, misfire, or engine shaking
- Reduced power and hesitation on acceleration
- Occasional stalling at idle
Common causes
Most likely first
- Weak, clogged, or leaking fuel injector on cylinder 1 (most common)Likely
- Low compression in cylinder 1 (valve or ring wear)Common
- Low fuel pressure or a fuel-delivery restriction to that cylinderCommon
- Wiring or connector fault at the cylinder 1 injectorLess often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and run an injector balance/contribution test to confirm cylinder 1 is weak.
- Check fuel pressure and inspect the cylinder 1 injector for clogging or leakage.
- Inspect the injector's wiring and connector.
- Run a compression test on cylinder 1 to rule out a mechanical cause.
- Clean or replace the injector as needed; address compression issues if found. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0263?+
Only briefly. A cylinder that isn't pulling its weight causes misfires that can overheat the catalytic converter, so get it diagnosed soon.
Can I just clear P0263?+
It comes back until the weak injector, fuel-delivery issue, or compression problem on cylinder 1 is repaired.
Related codes
Often seen with P0263
Read & clear P0263 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX