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Home/Cars/BMW/3 Series/E90/E91 (2005-2012)/how to fix P0301 code on BMW 3 Series E90/E91 (2005-2012)

how to fix P0301 code on BMW 3 Series E90/E91 (2005-2012)

BMW 3 Series E90/E91 (2005-2012)

Severity: mediumDifficulty: mediumError Code: P03012-4 hours
4 min read
649 words

Problem Statement

## Problem Statement The P0301 code indicates a misfire detected in cylinder 1 of a BMW 3 Series E90/E91 (2005-2012). This misfire can lead to rough engine operation and increased emissions.

Error Code
P0301
Repair Time
2-4 hours

Safety Warnings

  • ⚠Safety Warnings:**
  • ⚠Disconnect the battery before working on electrical systems.
  • ⚠Allow the engine to cool before performing any repairs.

Symptoms

  • •Check engine light illuminated
  • •Rough idle and engine vibration
  • •Loss of power during acceleration
  • •Poor fuel economy
  • •Possible engine stalling

Diagnostic Steps

  1. 1Scan for error codes using an OBD-II scanner to confirm the P0301 code.
  2. 2Inspect the spark plug for cylinder 1 for wear or damage.
  3. 3Check the ignition coil for cylinder 1 for proper function.
  4. 4Test fuel injector operation for cylinder 1.
  5. 5Perform a compression test on cylinder 1 to check for mechanical issues.
  6. 6Inspect vacuum lines and intake manifold for leaks that could affect cylinder performance.

Solution

Solution

1. Preparation

  • Gather necessary tools and parts.
  • Ensure the vehicle is parked on a flat surface and the engine is cool.
  • Disconnect the negative battery terminal.

2. Inspect and Replace Spark Plug

  • Tools Required: Socket set, spark plug socket, torque wrench.
  • Remove the ignition coil cover if necessary.
  • Disconnect the ignition coil connector for cylinder 1.
  • Remove the ignition coil by unscrewing the bolts and pulling it straight out.
  • Unscrew the spark plug with a spark plug socket.
  • Inspect the spark plug for wear or fouling. Replace with a new spark plug if needed (typically NGK or Bosch recommended).
  • Torque the new spark plug to the manufacturer’s specification (usually about 18 lb-ft).
  • Reinstall the ignition coil and connect the ignition coil connector.

3. Inspect and Replace Ignition Coil

  • If the spark plug is in good condition, test the ignition coil for cylinder 1.
  • Tools Required: Multimeter.
  • Test the primary and secondary resistance of the ignition coil according to specifications (typically 0.4-0.6 ohms for primary and 10-15 k ohms for secondary).
  • If the ignition coil fails the test, replace it with a new one.
  • Reinstall the ignition coil and reconnect the connector.

4. Check Fuel Injector

  • If both the spark plug and ignition coil are functioning correctly, check the fuel injector.
  • Tools Required: Fuel pressure gauge, multimeter.
  • Check fuel pressure at the fuel rail to ensure it meets specifications (typically around 50-60 psi).
  • Use a multimeter to check the injector’s resistance (should be around 12-14 ohms).
  • If the fuel injector is faulty, remove it and replace with a new one.

5. Compression Test

  • If misfire persists, perform a compression test.
  • Tools Required: Compression tester.
  • Remove spark plugs from all cylinders.
  • Insert the compression tester into the cylinder 1 spark plug hole.
  • Crank the engine and read the compression value (should be within manufacturer specifications, usually around 140-200 psi).
  • If compression is low, further inspection of the engine internals may be required.

Verification

After completing the repair, verify that the issue has been resolved:

  • Test the affected component to ensure it functions correctly
  • Check for any error codes or warning lights
  • Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

  • •Follow the manufacturer's recommended maintenance schedule
  • •Address warning signs early before they develop into major issues
  • •Use quality parts and fluids recommended for your vehicle
  • •Keep detailed records of all repairs and maintenance

Tools & Equipment Required

  • Remove the ignition coil cover if necessary.
  • Disconnect the ignition coil connector for cylinder 1.
  • Remove the ignition coil by unscrewing the bolts and pulling it straight out.
  • Unscrew the spark plug with a spark plug socket.
  • Torque the new spark plug to the manufacturer’s specification (usually about 18 lb-ft).
  • Reinstall the ignition coil and connect the ignition coil connector.

Parts Required

  • Spark plug (specific to BMW E90/E91)
  • Ignition coil (specific to BMW E90/E91)
  • Fuel injector (if necessary)

Additional Information

Error CodeP0301
Repair Time

2-4 hours

Difficulty

medium

Severity

medium

Tools

6 items

Parts

3 items

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