how to fix P0304 misfire code in Ram 1500 DT (2019-Present)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Ram 1500 DT. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

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

2. Replace Spark Plug

• Tools Required: Socket set (including 5/8" spark plug socket), torque wrench.
• Remove the ignition coil from cylinder 4:
  1. Unplug the electrical connector.
  2. Remove the mounting bolts.
  3. Gently pull the ignition coil out.
• Remove the spark plug:
  1. Use the spark plug socket to unscrew the spark plug.
  2. Inspect the old spark plug for wear or fouling.
• Install the new spark plug:
  1. Apply anti-seize lubricant to the threads of the new spark plug.
  2. Hand-tighten the spark plug, then torque to manufacturer specifications (typically 13-15 ft-lbs).
• Reinstall the ignition coil:
  1. Align it with the spark plug and press down.
  2. Replace bolts and reconnect the electrical connector.

3. Check and Replace Ignition Coil (if necessary)

• If the spark plug appears normal, test the ignition coil for cylinder 4:
  1. Use a multimeter to check primary and secondary resistance.
  2. If out of specification, replace the ignition coil with a new one.
• Follow the same installation steps as above for the ignition coil.

4. Inspect Fuel Injector

• If misfire persists, inspect the fuel injector for cylinder 4:
  1. Remove the fuel rail according to the service manual.
  2. Check the injector for clogs or leaks.
  3. Use a multimeter to test the injector's resistance—replace if faulty.
• Reinstall the fuel rail and ensure all connections are secure.

5. Verify Compression

• If no solutions have resolved the misfire, conduct a compression test:
  1. Remove spark plugs from all cylinders.
  2. Insert the compression gauge into the cylinder 4 spark plug hole.
  3. Crank the engine and record the pressure.
  4. Compare to manufacturer specifications; if low, further diagnostics may be required.