Loose or corroded cylinder 4 injector connector, or bent or pushed-out pins (OBD-Codes.com says this, or a faulty injector, is the typical cause in its author's experience). Internally shorted cylinder 4 fuel injector. Plugged or dirty cylinder 4 fuel injector. Faulty wiring harness between the engine computer and the injector (OBD-Codes.com says this is seldom faulty if left undisturbed). Failed fuel injection control module (FICM) or engine computer (PCM) (listed by RepairPal).

Clean or repair the cylinder 4 injector connector. Replace the cylinder 4 fuel injector if it is shorted or has failed (RepairPal lists injector replacement as the common repair). Clean the cylinder 4 injector if it is plugged or dirty (OBD-Codes.com describes a pressurized injector-cleaner flush through the fuel rail test port on gasoline engines, and says to replace the injector if the code returns afterward). Repair damaged wiring between the engine computer and the injector. Repair or replace the fuel injection control module or engine computer only after the injector, connector and wiring check out.

P0271⛽ Fuel injection / injector circuitStop and fix promptly

P0271: Cylinder 4 Injector Circuit High (Meaning, Causes, Fixes)

Q: What does P0271 mean?

P0271 means the engine computer has seen a high-voltage or high-current condition in the electrical circuit for the cylinder 4 fuel injector, so that injector is working poorly or not at all. OBD-Codes.com says the usual cause is a corroded or loose injector connector or a faulty injector, while RepairPal also lists a failed fuel injection control module (FICM) or engine computer and wiring problems. Fuel injectors are small electrically operated valves that spray fuel into each cylinder. RepairPal explains that the engine computer (PCM) uses special transistors called 'drivers' to switch the injectors on and off, and sets P0271 when it cannot control the cylinder 4 injector. OBD-Codes.com describes the code as an above-average current draw from the cylinder 4 injector, and notes that a loose connector adds resistance and raises the voltage needed to operate the injector. 'Cylinder 4' here refers to the cylinder numbered 4 by the manufacturer. The code is generic to OBD-II vehicles, but OBD-Codes.com points out that some manufacturers have had problems with particular batches of injectors or other parts, so the likely cause can vary by make. Search interest shows it often comes up on Ford's 6.0L Power Stroke diesel and on Peugeot and Hyundai, and RepairPal's list of causes includes the fuel injection control module (FICM) used on some diesels, so check technical service bulletins (TSBs) for your vehicle.

Q: Can I keep driving with P0271?

Stop and fix promptly. Get it diagnosed soon. RepairPal rates P0271 'Urgent', meaning it can cause severe damage, and OBD-Codes.com says it is better addressed as soon as possible because a bad fuel injector can affect the spark plug, cause detonation (engine knock) and harm the oxygen sensor and catalytic converter. If the check engine light is flashing, the engine shakes badly, or you smell raw fuel, keep driving to a minimum and have it checked. Fuel systems are under pressure, so don't open fuel lines with the engine running and let the engine cool before working near it.

Reviewed 2026-10-26 · Based on 2 cited source(s)

What P0271 means

Fuel injectors are small electrically operated valves that spray fuel into each cylinder. RepairPal explains that the engine computer (PCM) uses special transistors called 'drivers' to switch the injectors on and off, and sets P0271 when it cannot control the cylinder 4 injector. OBD-Codes.com describes the code as an above-average current draw from the cylinder 4 injector, and notes that a loose connector adds resistance and raises the voltage needed to operate the injector. 'Cylinder 4' here refers to the cylinder numbered 4 by the manufacturer. The code is generic to OBD-II vehicles, but OBD-Codes.com points out that some manufacturers have had problems with particular batches of injectors or other parts, so the likely cause can vary by make. Search interest shows it often comes up on Ford's 6.0L Power Stroke diesel and on Peugeot and Hyundai, and RepairPal's list of causes includes the fuel injection control module (FICM) used on some diesels, so check technical service bulletins (TSBs) for your vehicle.

Severity: can I keep driving?

Stop and fix promptly

Get it diagnosed soon. RepairPal rates P0271 'Urgent', meaning it can cause severe damage, and OBD-Codes.com says it is better addressed as soon as possible because a bad fuel injector can affect the spark plug, cause detonation (engine knock) and harm the oxygen sensor and catalytic converter. If the check engine light is flashing, the engine shakes badly, or you smell raw fuel, keep driving to a minimum and have it checked. Fuel systems are under pressure, so don't open fuel lines with the engine running and let the engine cool before working near it.

Common symptoms

Check engine light on
Rough idle (listed by OBD-Codes.com)
Lack of power or poor acceleration (OBD-Codes.com; RepairPal says decreased engine performance)
Worse fuel economy (OBD-Codes.com; RepairPal says increased fuel consumption)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Loose or corroded cylinder 4 injector connector, or bent or pushed-out pins (OBD-Codes.com says this, or a faulty injector, is the typical cause in its author's experience)
Internally shorted cylinder 4 fuel injector
Plugged or dirty cylinder 4 fuel injector
Faulty wiring harness between the engine computer and the injector (OBD-Codes.com says this is seldom faulty if left undisturbed)
Failed fuel injection control module (FICM) or engine computer (PCM) (listed by RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes. Other injector circuit codes (such as P0262, P0265 or P0268) appearing together can point to a shared wiring, power or control-module problem rather than one bad injector.
Look up technical service bulletins for your year, make and model.
Inspect the cylinder 4 injector connector, as OBD-Codes.com describes: look for bent or pushed-out pins, add dielectric grease, and push the connector on firmly so it is tight and its retaining clip is in place.
On a gasoline engine, OBD-Codes.com suggests listening to the injector with a long screwdriver (handle to your ear) while the engine runs. A clicking sound means it is working; no sound means it is not.
Clear the code and see if it returns. If it comes back after the connector checks out, the injector and circuit need testing.

Typical fixes

Clean or repair the cylinder 4 injector connector
Replace the cylinder 4 fuel injector if it is shorted or has failed (RepairPal lists injector replacement as the common repair)
Clean the cylinder 4 injector if it is plugged or dirty (OBD-Codes.com describes a pressurized injector-cleaner flush through the fuel rail test port on gasoline engines, and says to replace the injector if the code returns afterward)
Repair damaged wiring between the engine computer and the injector
Repair or replace the fuel injection control module or engine computer only after the injector, connector and wiring check out

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

OBD-Codes.com describes unplugging the injector and measuring its resistance across the two terminals with an ohmmeter, quoting 0.5 to 2.0 ohms as good. Injector resistance specs vary by injector type, so compare the reading against the factory specification for your engine rather than a general figure
The sources differ: OBD-Codes.com puts the connector and injector first and says the harness is seldom faulty, while RepairPal's list of common causes also includes a failed fuel injection control module (FICM), a failed PCM and wiring issues
Diesel engines use high-pressure injection systems and, on some engines, a separate injector control module, which work differently from the gasoline layout OBD-Codes.com describes; testing and repair on those is best left to a shop with the right scan tool and factory procedure
The code returns after the connector has been repaired and the injector cleaned or replaced, or several injector circuit codes set at once

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0271?

Only as much as you need to. RepairPal rates it 'Urgent', and OBD-Codes.com says to fix it as soon as possible because a bad injector can cause detonation and damage the spark plug, oxygen sensor and catalytic converter. If the engine shakes badly or the check engine light flashes, limit driving and get it checked.

Is P0271 always a bad injector?

No. OBD-Codes.com says a corroded or loose injector connector is just as common a cause as a faulty injector in its author's experience, and RepairPal also lists wiring, the engine computer and the fuel injection control module. Check the connector first.

What's the difference between P0270, P0271 and P0272?

All three involve cylinder 4. P0270 means the engine computer saw low voltage in the cylinder 4 injector circuit, and P0271 means it saw high voltage or excessive current draw. P0272 is different: it means cylinder 4 is contributing less power than the others.

Why does P0271 come up on the Ford 6.0 Power Stroke?

Our sources don't single out any engine. The code is generic, but RepairPal's list of common causes includes a failed fuel injection control module (FICM), the separate injector control module used on some diesels, alongside the injector, the engine computer and wiring. On a diesel like the 6.0, have a diesel shop check the FICM, injector and wiring with the right scan tool, and look up technical service bulletins for your vehicle.

Sources

Last reviewed 2026-10-26. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.