how to fix P0304 code in Ford F-150 13th Generation (2015-2020)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Ford F-150 (2015-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, compression tester, multimeter, noid light, torque wrench.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Locate and remove the ignition coil for cylinder 4 by unscrewing the mounting bolts.
  3. Disconnect the electrical connector from the ignition coil.
  4. Unscrew and remove the spark plug using a socket.
  5. Inspect the old spark plug for wear; replace with a new spark plug that matches OEM specifications (usually Motorcraft SP-534).
  6. Install the new spark plug to the manufacturer's torque specification (usually around 13-15 lb-ft).
  7. Reattach the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil (if necessary)

• Sub-steps:
  1. If the ignition coil is damaged, replace it with a new one that matches OEM specifications.
  2. Install the new ignition coil, ensuring it is seated properly and secured with the mounting bolts.
  3. Reconnect the electrical harness to the ignition coil.

4. Inspect and Replace Fuel Injector (if necessary)

• Sub-steps:
  1. Remove the fuel rail if necessary to access the fuel injector for cylinder 4.
  2. Using a noid light, check for proper signal to the fuel injector.
  3. If no signal is present, inspect wiring; if the injector is faulty, replace it with a new one.
  4. Reinstall the fuel rail and make sure all connections are secure.

5. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 4.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine and note the compression reading; it should be within the manufacturer's specified range (usually 120-150 psi).
  4. If compression is low, further investigation into internal engine issues may be required.