Cylinder 4 High Injector Circuit

📌 What is the P0271 code?

The P0271 code is a generic OBD-II diagnostic code that indicates an electrical or mechanical problem with the fuel injector of cylinder number 4. It is often interpreted as:

“Cylinder 4 Injector – High Current Consumption”

This means that the injector is drawing more current than expected, which may indicate a stuck injector, short circuit, or connection issue.

---

⚠️ Possible Symptoms

• ✅ Check Engine Light (MIL) on

• 🚗 Rough idle

• 🔧 Lack of power or misfires

• 💨 Increased emissions

• ⛽ Higher fuel consumption

---

🛠️ Possible Causes

1. Faulty fuel injector (short circuit or clogging)

2. Corroded or poorly connected injector connector

3. Damaged wiring between the ECU (PCM) and the injector

4. Incorrect electrical resistance of the injector

5. Lubrication problem related to E10/E85 fuel (ethanol)

---

🧪 Recommended Diagnostic Procedure

🔧 Step 1: Checking the Injector Connector

• Visually inspect the cylinder 4 injector connector.

• Look for bent pins, corrosion, excessive play, etc.

• Clean with contact spray and apply dielectric grease before reconnecting.

🔍 Step 2: Injector Activity Test

• Use a long screwdriver as a stethoscope (or a specialized tool) to listen for the injector click during operation.

• No sound = stuck injector.

📏 Step 3: Resistance Measurement

• Disconnect the injector and measure the resistance between its two terminals.

  • Normal value: 0.5 to 2 ohms

  • Less or more = injector potentially short-circuited or open.

🧼 Step 4: Injector Cleaning (if resistance is OK)

• Use a direct injection cleaning kit (cleaner + adapter).

• Procedure:

  1. Remove the fuel pump fuse, run the engine until it stops.

  2. Connect the cleaning kit to the injection rail.

  3. Start the engine with the cleaner until it stalls.

  4. Put everything back in place (fuse, Schrader valve, etc.).

  5. Restart and test.

---

✅ Conclusion / What to do if the code returns?

• If after cleaning the injector still malfunctions or the code returns, replace it.

• Replacing a fuel injector remains a reliable solution and is often necessary.