how to fix P0303 misfire code in Toyota Highlander Third Generation (2014-2019)

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0303

4 min read

610 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 Toyota Highlander (2014-2019). 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 components.
•Relieve fuel pressure before removing fuel injectors.

Symptoms

•Check engine light illuminated
•Engine stalling or rough idle
•Reduced engine power
•Increased fuel consumption
•Engine noise or vibration

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0303 is present.
2
Inspect the spark plug for cylinder 3 for wear or damage.
3
Check the ignition coil for cylinder 3 for proper operation.
4
Verify fuel injector operation for cylinder 3.
5
Perform a compression test on cylinder 3 to check for mechanical issues.
6
Inspect for vacuum leaks near cylinder 3 or intake manifold.

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
•Fuel injector cleaner

Parts Required

•Spark plug (for cylinder 3)
•Ignition coil (for cylinder 3)
•Fuel injector (if cleaning or replacement is necessary)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0303 is present.
2
Inspect the spark plug for cylinder 3 for wear or damage.
3
Check the ignition coil for cylinder 3 for proper operation.
4
Verify fuel injector operation for cylinder 3.
5
Perform a compression test on cylinder 3 to check for mechanical issues.
6
Inspect for vacuum leaks near cylinder 3 or intake manifold.

Solution

1. Preparation

Gather all necessary tools and parts.
Ensure the vehicle is parked on a level surface and the engine is cool.
Disconnect the negative battery terminal to prevent any electrical short circuits.

2. Inspect and Replace Spark Plug

Tools Required: Socket set, torque wrench
Remove the engine cover if applicable.
Locate the spark plug for cylinder 3 (consult the service manual for exact location).
Use a socket wrench to carefully remove the spark plug.
Inspect the spark plug for signs of wear, carbon buildup, or damage.
If damaged, replace it with a new spark plug, ensuring it is gapped correctly to manufacturer specifications (typically 0.043 inches for this model).
Torque the new spark plug to 13 ft-lbs (17 Nm).

3. Inspect and Replace Ignition Coil

Tools Required: Socket set, multimeter
After replacing the spark plug, disconnect the ignition coil connector for cylinder 3.
Remove the ignition coil using a socket wrench.
Test the ignition coil with a multimeter (primary resistance should be within manufacturer specs).
If the coil is faulty, replace it with a new ignition coil.
Reinstall the ignition coil and reconnect the electrical connector.

4. Check and Clean Fuel Injector

Tools Required: Fuel injector cleaner, socket set
Disconnect the fuel injector connector for cylinder 3.
Remove the fuel injector from the rail (ensure fuel pressure is relieved before removing).
Clean the injector using a specialized fuel injector cleaner or replace it if necessary.
Reinstall the injector securely and reconnect the electrical connector.

5. Compression Test

Tools Required: Compression tester
Attach the compression tester to the spark plug hole of cylinder 3.
Crank the engine and check the compression reading. Compare it to manufacturer specifications (typically around 150 psi).
If the compression is low, further investigation is required for potential internal engine issues.