how to fix P0303 code in Toyota Corolla E170 (2013-2019)

Toyota Corolla E170 (2013-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0303

3 min read

578 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 Corolla E170 (2013-2019). 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 systems.
•Relieve fuel pressure before servicing fuel injectors to avoid fuel spray.

Symptoms

•Check engine light illuminated
•Rough idle or hesitation during acceleration
•Decreased engine power
•Poor fuel economy
•Engine stalling or difficulty starting

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0303 and check for any related codes.
2
Inspect the spark plug and ignition coil in cylinder 3 for visible damage or wear.
3
Test the ignition coil operation by swapping it with a functioning coil from another cylinder and check for a change in misfire.
4
Check the fuel injector for proper operation by performing a resistance test and ensuring it's not clogged.
5
Perform a compression test on cylinder 3 to rule out mechanical issues such as low compression.
6
Inspect for vacuum leaks around the intake manifold and throttle body that may affect cylinder performance.

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
•Spark plug socket
•Fuel pressure gauge

Parts Required

•Spark plug(s)
•Ignition coil (if faulty)
•Fuel injector (if faulty)

Related Faults

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0303 and check for any related codes.
2
Inspect the spark plug and ignition coil in cylinder 3 for visible damage or wear.
3
Test the ignition coil operation by swapping it with a functioning coil from another cylinder and check for a change in misfire.
4
Check the fuel injector for proper operation by performing a resistance test and ensuring it's not clogged.
5
Perform a compression test on cylinder 3 to rule out mechanical issues such as low compression.
6
Inspect for vacuum leaks around the intake manifold and throttle body that may affect cylinder performance.

Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the battery to ensure safety while working on electrical components.

2. Spark Plug Replacement

Tools Required: Socket set, torque wrench, spark plug socket.
Remove the ignition coil cover (if applicable).
Disconnect the electrical connector from the ignition coil on cylinder 3.
Remove the ignition coil using a socket.
Remove the spark plug using a spark plug socket.
Install a new spark plug with a gap of 0.044 inches (1.1 mm) and torque to 13 lb-ft (18 Nm).
Reinstall the ignition coil and reconnect the electrical connector.

3. Ignition Coil Testing/Replacement

If the ignition coil was found faulty during diagnostics, replace it:
- Remove the defective ignition coil as described above.
- Install a new ignition coil and torque to the manufacturer specifications (usually around 10 lb-ft or 14 Nm).
- Reinstall the ignition coil cover.

4. Fuel Injector Testing/Replacement

If the injector was found faulty:
- Disconnect the fuel pump relay and start the engine until it stalls to relieve fuel pressure.
- Remove the fuel injector wiring harness.
- Unbolt and remove the fuel rail to access the injector.
- Replace the faulty fuel injector, ensuring to lubricate the O-ring with clean engine oil before installation.
- Reassemble the fuel rail and reconnect the wiring harness.

5. Reassemble and Clear Codes

Reconnect the battery.
Use the OBD-II scanner to clear the P0303 code.
Start the engine and observe for any check engine light re-illuminating.