P0271 Cylinder 4 Injector Circuit High

P0271 points to a high injector circuit on cylinder 4. The injector 4 circuit is open, shorted to voltage, or above expected range.

Code details

Generic OBD-II · P0

System: Injector
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not assume injector 4 is mechanically stuck until the high circuit is electrically isolated.

Symptoms of P0271

Check-engine light, often with a misfire feel from one cylinder.
Rough idle, hesitation, or a slight loss of power.
Higher fuel use, or in some cases a fuel smell.

Common causes of P0271

A stuck, leaking, clogged, or electrically failed injector.
Injector wiring, connector, or driver-circuit faults.
Low fuel pressure or contamination affecting injector behaviour.

Useful checks before replacing parts

Check injector 4 signal voltage, feed supply, ground control, open circuits, short-to-voltage faults, and injector resistance.
Compare cylinder 4 balance, misfire, contribution, and injector command data with adjacent cylinders under similar load.
Inspect terminal fit, connector corrosion, harness heat damage, water intrusion, and controller driver behavior during loaded testing.

Related OBD-II codes

These nearby injector entries can help compare wording and pin down the fault area.