how to fix a check engine light on my Ram 1500 DT (2019-Present) with code P0303?

Learn how to diagnose and fix P0303 cylinder 3 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.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Compression tester
• Screwdriver set

2. Replace Spark Plug

• Remove the engine cover if necessary to access the spark plug.
• Use a socket wrench to remove the spark plug from cylinder 3.
• Inspect the old spark plug for signs of wear or oil fouling.
• Install a new spark plug and torque it to the manufacturer’s specifications (typically 13-15 lb-ft).

3. Test and Replace Ignition Coil

• Disconnect the ignition coil connector for cylinder 3.
• Check the resistance of the ignition coil with a multimeter; it should be within manufacturer specifications (typically around 0.5-1.5 ohms).
• If the ignition coil is faulty, replace it with a new one.
• Reconnect the ignition coil connector.

4. Inspect Fuel Injector

• Remove the fuel injector connector for cylinder 3.
• Perform a balance test by using a noid light or an oscilloscope to ensure the injector is firing.
• If the injector is faulty, replace it with a new one.
• Reconnect the injector connector.

5. Perform Compression Test

• Remove the spark plug for cylinder 3 again.
• Insert the compression tester into the spark plug hole and crank the engine.
• Record the compression reading; it should be within the engine’s specifications (usually around 120-200 psi).
• If the compression is low, further investigation into internal engine issues is required.