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DTC codes / P02xx · Fuel and air metering (injector circuits) / P0271

P0271Cylinder 4 Injector Circuit High

P0271 means the engine computer has detected abnormally high current flow in the electrical circuit that operates the fuel injector for cylinder 4. The computer monitors the injector driver circuit and sets this code when the current exceeds the expected range, indicating a short to voltage or a low-resistance path in the wiring or injector itself.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire felt as a shake or stumble, especially noticeable at idle
  • Loss of power or hesitation during acceleration
  • Poor fuel economy due to incomplete combustion in cylinder 4
  • Possible fuel smell from the exhaust if the injector is stuck open
  • In some cases, the engine may enter limp mode or shut off the affected cylinder

Common causes, most likely first

  1. Faulty fuel injector with an internally shorted coil
  2. Chafed or shorted wire in the injector harness touching a power source
  3. Corroded or damaged injector connector pins causing a short
  4. Short to voltage in the injector driver circuit between the ECM and injector
  5. Internal short in the engine control module (ECM) injector driver
  6. Aftermarket or incorrect injector with wrong resistance installed
  7. Moisture intrusion in the injector connector or wiring harness

How to diagnose and fix it

  1. Inspect the injector connector and wiring for visible damage, corrosion, or chafing
  2. Disconnect the injector and measure resistance across its terminals; compare to specification
  3. Check for short to voltage on the injector control wire with a multimeter while wiggling the harness
  4. Swap the cylinder 4 injector with a known-good injector from another cylinder and see if the code moves
  5. Test the injector driver circuit from the ECM side for a short to power
  6. If the injector is internally shorted, replace it and clear the code
  7. If the wiring is shorted, repair the harness and re-test the circuit

Don't overlook the injector harness

  • A common misdiagnosis is replacing the injector when the real fault is a chafed wire shorting to ground or power near the intake manifold.
  • The code can be set by a short to voltage on the control wire, which may only appear when the engine is hot or vibrating, so wiggle tests are essential.
  • Aftermarket injectors with incorrect resistance are a frequent cause, especially after a recent repair or engine swap.
  • A shorted injector can flood the cylinder with fuel, leading to bore wash and premature engine wear if driven for long.
  • The ECM driver can be damaged by a shorted injector, so always check injector resistance before installing a new ECM.

Can I keep driving with P0271?

Driving with P0271 is not recommended because a shorted injector can dump excess fuel into the cylinder, causing rich running, potential catalytic converter damage, and engine wear. If you must drive to a repair shop, keep the trip short and avoid heavy acceleration or high speeds.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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