how to diagnose P0303 misfire code on Ford F-150 13th Generation (2015-2020)

Ford F-150 13th Generation (2015-2020)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0303

4 min read

673 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix P0303 cylinder 3 misfire in Ford F-150 (2015-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code

P0303

Affected Component

Engine

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Decreased fuel efficiency
•Engine stalling or hesitation during acceleration
•Increased exhaust emissions
•Unusual engine noises, such as backfiring

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm the presence of the P0303 code and any other related codes.
2
Inspect the spark plug in cylinder 3 for wear or damage; replace if necessary.
3
Check the ignition coil for cylinder 3 by swapping it with another cylinder and monitoring for changes in misfire codes.
4
Examine the fuel injector functionality in cylinder 3 using a noid light or a multimeter to ensure it is receiving power and functioning correctly.
5
Perform a compression test on cylinder 3 to check for mechanical issues such as low compression due to worn rings or a blown head gasket.
6
Inspect the wiring and connectors related to the ignition system and fuel injector for any signs of wear, corrosion, or disconnection.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

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

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

Parts Required

•Spark plug (if worn or damaged)
•Ignition coil (if faulty)
•Fuel injector (if malfunctioning)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm the presence of the P0303 code and any other related codes.
2
Inspect the spark plug in cylinder 3 for wear or damage; replace if necessary.
3
Check the ignition coil for cylinder 3 by swapping it with another cylinder and monitoring for changes in misfire codes.
4
Examine the fuel injector functionality in cylinder 3 using a noid light or a multimeter to ensure it is receiving power and functioning correctly.
5
Perform a compression test on cylinder 3 to check for mechanical issues such as low compression due to worn rings or a blown head gasket.
6
Inspect the wiring and connectors related to the ignition system and fuel injector for any signs of wear, corrosion, or disconnection.

Solution

1. Preparation

Gather tools and materials.
Disconnect the negative battery terminal to ensure safety.
Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester.

2. Replace Spark Plug

Remove the engine cover if applicable.
Disconnect the spark plug wire or ignition coil connector from cylinder 3.
Use a socket wrench to remove the spark plug from cylinder 3.
Inspect the spark plug for signs of excessive wear or deposits; replace if necessary.
Install a new spark plug, tightening it to the manufacturer's specified torque (typically around 13-15 lb-ft).
Reconnect the spark plug wire or ignition coil connector.

3. Test and Replace Ignition Coil (if necessary)

Swap the ignition coil from cylinder 3 with another cylinder.
Clear the P0303 code using the OBD-II scanner and start the engine.
Monitor for any new misfire codes; if the code moves to the cylinder where the coil was swapped, replace the ignition coil at cylinder 3.
Install the new ignition coil and reconnect the electrical connector.

4. Inspect and Replace Fuel Injector (if necessary)

Disconnect the fuel injector connector from cylinder 3.
Use a noid light or multimeter to check for power to the fuel injector.
If no power is detected, trace wiring back to the ECM and repair as necessary.
If power is present and the injector is faulty, remove the fuel rail to access the injector.
Replace the fuel injector with a new one and reassemble the fuel rail.

5. Perform Compression Test

Remove the spark plug from cylinder 3.
Insert a compression tester into the spark plug hole and crank the engine.
Record the compression reading; it should be within manufacturer specifications (usually between 120-150 psi).
If compression is low, investigate further for potential internal engine issues.