Cylinder 4 Injector Circuit High
P0271 indicates that the fuel injector circuit for cylinder 4 is detecting a high voltage condition, meaning the injector is not operating correctly or the circuit has an electrical fault. This prevents proper fuel delivery to that cylinder, causing misfires and engine performance issues.
What You Might Notice
- Malfunction indicator light (Check Engine) illuminated
- Rough idle or misfiring in cylinder 4
- Poor fuel economy
- Lack of power and poor acceleration
- Engine running rough under load
Most Common Causes
- 1
Faulty fuel injector
The injector for cylinder 4 may be stuck open, electrically shorted, or internally damaged, causing the high voltage signal.
- 2
Damaged electrical harness or connector
The wiring to the cylinder 4 injector may be corroded, pinched, or shorted, creating high resistance or short circuit conditions.
- 3
Engine control module (ECM) malfunction
The ECM injector driver circuit may be faulty, failing to properly control the injector solenoid.
- 4
High fuel pressure condition
Excessive fuel pressure can cause the injector to remain partially open or leak, creating an abnormal electrical signature.
How to Diagnose It
- 1
Check Faulty fuel injector — The injector for cylinder 4 may be stuck open, electrically shorted, or internally damaged, causing the high voltage signal.
- 2
Check Damaged electrical harness or connector — The wiring to the cylinder 4 injector may be corroded, pinched, or shorted, creating high resistance or short circuit conditions.
- 3
Check Engine control module (ECM) malfunction — The ECM injector driver circuit may be faulty, failing to properly control the injector solenoid.
- 4
Check High fuel pressure condition — Excessive fuel pressure can cause the injector to remain partially open or leak, creating an abnormal electrical signature.
How to Fix It
- 1
Inspect and test fuel injector #4
Use a multimeter to test the injector coil resistance and continuity. If out of specification or no continuity exists, replace the fuel injector.
- 2
Check and repair injector harness and connector
Inspect the wiring harness and connector for cylinder 4 injector for corrosion, damage, or loose pins. Repair or replace the harness as needed and ensure proper connector seating.
- 3
Verify fuel pressure
Connect a fuel pressure gauge to check system pressure against manufacturer specifications. If pressure is high, inspect and replace the fuel pressure regulator if necessary.
- 4
Check engine control module
If all other components test normal, have the ECM scanned with a professional diagnostic tool or reflashed by a qualified technician, as the injector driver circuit may be faulty.
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