What causes fault code P0271?

• Most likely: Fuel injector wiring harness shorted to voltage • Likely: Failing fuel injector (internal short) • Possible: Corroded or damaged connector causing cross-talk/short • Rare: Internal Engine Control Module (ECM) failure

How do you fix fault code P0271?

STEP 1: Inspect the fuel injector connector for cylinder 4 for signs of backing out or corrosion. Clean as necessary. STEP 2: Use a multimeter to check the internal resistance of the injector. Typical values are 12-16 Ohms. Replace if out of spec. STEP 3: Check the wiring harness for a short to voltage. With ignition ON and injector disconnected, verify there is no unwanted voltage on the signal wire. STEP 4: If wiring and injector are okay, a bench test of the ECM or replacement may be required.

Powertrain (Engine & Gearbox)Standard EOBD

P0271 - Cylinder 4 Injector Circuit High

Q: What are the symptoms of fault code P0271?

• Check Engine Light (MIL) illumination • Engine misfire on cylinder 4 • Rough idling and hesitation during acceleration • Reduced engine power and 'Limp mode' • Increased fuel consumption

Last updated:1 February 2026

Related:Fuel Injector, Engine Control Unit (ECU), Wiring Harness, Spark plug (consequential fault)

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0200

Injector Circuit Malfunction

P0201

Cylinder 1 Injector Circuit Open

P0202

Injector Circuit - Cylinder 2 - Malfunction

P0203

Injector Circuit - Cylinder 3

Technical Description

P0271 is set when the Engine Control Module (ECM) detects an abnormally high voltage in the fuel injector control circuit for cylinder 4. This typically indicates a short to voltage (B+) within the wiring harness or the injector itself. Since injectors are usually ground-side controlled by the ECM, a constant high voltage state prevents correct pulse-width modulation, leading to fuel delivery failure and potential engine damage.

Possible Causes

Fuel injector wiring harness shorted to voltage

Failing fuel injector (internal short)

Corroded or damaged connector causing cross-talk/short

Internal Engine Control Module (ECM) failure

Symptoms

Check Engine Light (MIL) illumination

Engine misfire on cylinder 4

Rough idling and hesitation during acceleration

Reduced engine power and 'Limp mode'

Increased fuel consumption

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P0271 - Cylinder 4 Injector Circuit High

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P0271 - Cylinder 4 Injector Circuit High

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