P0271 Fault Code

P0271 OBD-II Trouble Code Short Description

Cylinder #4 Injector Circuit High

What does trouble code P0271 mean?

The P0271 fault code refers to a problem with the cylinder #4 injector circuit in a fuel-injected engine. When this code is triggered, it means that the Engine Control Module (ECM) has detected a high voltage or resistance in the injector circuit of cylinder #4.

There are several possible causes for this issue. It could be a faulty injector, a wiring problem in the circuit, or a problem with the ECM itself. It is important to note that this code specifically relates to cylinder #4, so the issue is isolated to that particular cylinder.

To diagnose and resolve this issue, a few steps can be taken. First, the wiring and connections related to the cylinder #4 injector should be inspected for any damage or loose connections. If any issues are found, they should be addressed and repaired.

Next, an electrical test can be performed on the injector itself to check for proper voltage and resistance using a digital multimeter. If the injector is found to be faulty, it will need to be replaced.

If all of the above steps do not resolve the issue, further diagnosis may be needed to determine if there is a fault with the ECM. This may require the use of diagnostic tools and software to pinpoint the exact cause of the high voltage or resistance in the circuit.

In conclusion, the P0271 fault code indicates a problem with the cylinder #4 injector circuit. Proper diagnosis and troubleshooting are necessary to identify and resolve the specific cause, which may involve inspecting the wiring, testing the injector, or checking the ECM.


What are the symptoms of the P0271 code?

  • Engine misfires or runs rough: You may notice a noticeable loss of power or a shaking sensation coming from the engine.
  • Rough idling: The engine may have difficulty maintaining a steady idle speed and may stutter or fluctuate in RPM.
  • Decreased fuel efficiency: The vehicle may require more fuel to operate efficiently, resulting in decreased fuel economy.
  • Reduced acceleration and throttle response: You may experience a delay or lack of response when accelerating or pressing the throttle.
  • Check Engine Light (CEL) illuminated: The vehicle's onboard diagnostic system will detect the fault and trigger the CEL to indicate a problem.
  • Fuel odor: In some cases, you may detect a fuel odor either inside or outside the vehicle.
  • Increased emissions: The vehicle may produce higher levels of pollutants due to improper fuel injection in one cylinder.
  • Hard starting: The engine may have difficulty starting or may take longer to start than usual.


What causes the P0271 code?

The P0271 fault code is associated with a problem in the cylinder #4 injector circuit. This code is specific to fuel-injected engines. The possible causes for this fault code include:

  1. Faulty injector: The injector itself may be faulty or clogged, preventing it from delivering the correct amount of fuel to the cylinder.

  2. Wiring issues: There could be a problem with the wiring harness or connector that leads to the cylinder #4 injector. This can result in a high resistance or open circuit, causing the code to be triggered.

  3. PCM (powertrain control module) failure: The PCM, which controls the fuel injection system, may be malfunctioning or failing to provide the correct signals to the injector. This can lead to the injector circuit voltage being too high.

  4. ECU (engine control unit) limitations: In some cases, aftermarket modifications or tuning can exceed the ECU's capabilities, leading to higher than normal injector circuit voltage.

  5. Other possible causes: Issues with the fuel supply, such as a clogged fuel filter or low fuel pressure, can also contribute to this fault code.

It is important to note that diagnosing and repairing the cause of this fault code requires proper diagnostic equipment and skills. It is recommended to seek professional assistance to accurately identify and address the underlying issue.

Possible Solutions

How to fix P0271?

The P0271 fault code refers to the Cylinder #4 Injector Circuit High. This code indicates that there is an issue with the fuel injector circuit for cylinder #4, and it is experiencing a high voltage condition.

To fix this fault code on cars, you can follow the steps below:

  1. Check the wiring: Inspect the wiring harness and connector for any signs of damage or corrosion. Make sure all connectors are securely connected. Repair or replace any damaged wiring.

  2. Inspect the fuel injector: Check the fuel injector for any signs of damage or clogs. Clean or replace the fuel injector if necessary.

  3. Test the fuel injector circuit: Use a multimeter to test the resistance of the fuel injector circuit. Compare the readings with the manufacturer's specifications. If the resistance is abnormal, replace the faulty injector or repair the circuit.

  4. Check the fuel pressure: Inspect the fuel pressure to ensure it is within the manufacturer's specifications. Low fuel pressure can cause injector circuit issues. Repair or replace any components that are causing low fuel pressure.

  5. Scan and clear the fault code: After performing the necessary repairs, use a diagnostic scanner to clear the fault code. This will reset the check engine light.

If the fault code still persists after performing these steps, it is recommended to consult with a professional mechanic or authorized service center for further diagnosis and repair.