AutoFixDB - Free OBD-II diagnostic trouble code lookup. Find causes, symptoms, diagnostic steps and repair solutions.

Overview

P0271 indicates an OBD-II generic trouble code meaning an abnormally high voltage or resistance condition detected in the fuel injector circuit for cylinder 4, often due to electrical, injector, or controller faults.

Common Symptoms

Check Engine Light is illuminated
Rough or uneven idle
Reduced engine performance or loss of power
Occasional misfire on cylinder 4
Higher than normal fuel consumption

Most Common Causes

Faulty fuel injector (cylinder 4) high

Injector internal short or failure can raise circuit voltage beyond expected range

Damaged or corroded wiring/connectors in injector circuit high

Broken, frayed, corroded, or loose connectors increase resistance and trigger high circuit reading

PCM/ECM driver circuit failure medium

Powertrain control module output transistor for the injector may fail, causing abnormal voltage

Voltage spikes or electrical supply issues medium

Charging system anomalies or grounding problems can introduce high readings

Diagnostic Steps

Scan vehicle with an OBD-II tool and confirm P0271 and any related codes

Expected: P0271 stored; potential additional codes like misfire codes for cylinder 4

Interpretation: Code confirmed; related codes may provide more context
Visually inspect wiring harness and connectors for cylinder 4 injector

Expected: No frayed wires, corrosion, or loose pins

Interpretation: If faults found, likely source of abnormal circuit readings
Measure resistance of injector 4 with a multimeter against manufacturer specification

Expected: Resistance within expected range

Interpretation: Out-of-spec readings suggest injector internal fault
With engine running/cranking, measure voltage at injector circuit

Expected: Voltage within normal operating range

Interpretation: Excessive voltage indicates wiring or PCM driver issue
Test PCM driver output and consider software update or reflash

Expected: Proper driver function

Interpretation: Faulty PCM driver requires module repair/replacement

Repair Solutions

Replace faulty fuel injector (cylinder 4) medium

Estimated Cost: $200 - $500

Cost varies by vehicle and whether OEM or aftermarket parts

Repair or replace wiring/connectors medium

Estimated Cost: $50 - $200

Depends on extent of harness damage

PCM/ECM reprogramming or replacement hard

Estimated Cost: $500 - $1500

Required if driver circuit inside PCM is faulty

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Assuming a misfire is only a spark plug or ignition coil without testing injector circuit
Replacing the injector without checking wiring harness integrity first

Frequently Asked Questions

Technical definition of P0271 OBD-II Code

When your OBD-II scanner reads P0271, it means: Cylinder 4 Injector Circuit High. This code is related to the vehicle's Fuel System.

Is it safe to drive with a P0271 code?

You should treat P0271 as a medium issue. Check engine light illumination; rough idle; potential misfire on cylinder 4; reduced engine power; poorer fuel economy

What happens when the P0271 code is active?

The most typical signs are: Check Engine Light is illuminated, Rough or uneven idle, Reduced engine performance or loss of power.

What parts fail when P0271 is set?

The most common causes are: Faulty fuel injector (cylinder 4), Damaged or corroded wiring/connectors in injector circuit, PCM/ECM driver circuit failure.

Repair cost breakdown for P0271

The cost varies significantly based on the root cause. For example, replacing a Repair or replace wiring/connectors typically costs between $50 and $200, while fixing a PCM/ECM reprogramming or replacement can range from $500 to $1500.

What cars are affected by the P0271 code?

This is a universal code. You might see P0271 on Ford, Chevrolet, Toyota, Honda, Nissan, or any other OBD-II vehicle.

P0271: Cylinder 4 Injector Circuit High