P0271
Cylinder 4 Injector A Circuit High
Fuel injector circuit
Generic OBD-II
High
What it means
P0271 means the control module detects an abnormally high voltage on the cylinder-4 injector control circuit — typically a short to voltage or an injector fault. When the injector can't be driven correctly, cylinder 4 misfires, so the engine runs rough and loses power. A sustained misfire can also damage the catalytic converter, so it's worth prompt attention.
High
Can I keep driving? Cylinder 4 may drop out and misfire, so the engine runs rough and down on power; drivable short distances, but a persistent misfire can harm the catalytic converter.
Common symptoms
What you'll notice
- Check-engine light on
- Rough idle or a misfire from cylinder 4
- Reduced power and hesitation
- Increased fuel consumption or a fuel smell
Common causes
Most likely first
- Short to voltage in the cylinder-4 injector control wiringLikely
- Faulty injector for cylinder 4Common
- Corroded or loose connector at the injectorCommon
- Failed injector driver in the PCM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the fault is on the cylinder-4 injector circuit.
- Inspect the injector connector and wiring for a short to voltage, chafing, or corrosion.
- Measure the injector's resistance and compare it to the other injectors.
- Swap the suspect injector with a known-good cylinder to see if the fault follows it.
- Replace the injector or repair the wiring as indicated; consider the PCM driver only last. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0271?+
Only briefly. A dead or misfiring cylinder loads unburnt fuel into the exhaust, which can overheat and damage the catalytic converter.
Can I just clear P0271?+
It returns quickly because the injector circuit fault is still present. The wiring or injector must be repaired.
Related codes
Often seen with P0271
Read & clear P0271 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