how to fix P0420 code on my Toyota Highlander Third Generation (2014-2019)

Toyota Highlander Third Generation (2014-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0420

3 min read

548 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 P0420 exhaust system issue in Toyota Highlander (2014-2019). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code

P0420

Affected Component

Exhaust System

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the exhaust system to cool before touching components to prevent burns.

Symptoms

•Check engine light illuminated
•Decreased fuel efficiency
•Failed emissions test
•Sulfur smell from exhaust
•Rough engine idle

Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to confirm the P0420 code and check for any other related codes.
2
Inspect the exhaust system visually for any signs of damage, leaks, or loose connections.
3
Check the oxygen sensors (pre-catalytic converter and post-catalytic converter) for functionality and proper voltage readings using a multimeter.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter to assess its efficiency.
5
Inspect for any exhaust leaks upstream of the catalytic converter that could affect sensor readings.

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
•Oxygen sensor socket
•Torque wrench
•Multimeter
•Jack and jack stands

Parts Required

•New oxygen sensors (if faulty)
•New catalytic converter (if needed)
•Exhaust gaskets (if required)

Related Faults

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Diagnostic Steps

1
Scan the vehicle's onboard diagnostic system using an OBD-II scanner to confirm the P0420 code and check for any other related codes.
2
Inspect the exhaust system visually for any signs of damage, leaks, or loose connections.
3
Check the oxygen sensors (pre-catalytic converter and post-catalytic converter) for functionality and proper voltage readings using a multimeter.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter to assess its efficiency.
5
Inspect for any exhaust leaks upstream of the catalytic converter that could affect sensor readings.

Solution

1. Preparation

Gather tools and parts.
Disconnect the negative battery terminal to prevent electrical shorts.
Raise and support the vehicle using jack stands if necessary.

2. Inspect and Replace Oxygen Sensors (if faulty)

Sub-steps:
1. Locate the upstream (pre-cat) and downstream (post-cat) oxygen sensors.
2. Disconnect the electrical connectors from both sensors.
3. Using an oxygen sensor socket, carefully remove the sensors from the exhaust manifold and catalytic converter.
4. Install new oxygen sensors by threading them into their respective locations and tightening to manufacturer specifications (generally around 30 ft-lbs).
5. Reconnect the electrical connectors to the oxygen sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

Sub-steps:
1. Locate the catalytic converter in the exhaust system.
2. Disconnect the exhaust pipes before and after the catalytic converter using a socket set.
3. Remove any heat shields or brackets holding the catalytic converter in place.
4. Install the new catalytic converter, making sure to align it properly with the exhaust pipes.
5. Tighten all connections to the manufacturer’s torque specifications.
6. Reinstall any heat shields or brackets that were removed.

4. Reset the Engine Control Module (ECM)

Sub-steps:
1. Reconnect the negative battery terminal.
2. Use an OBD-II scanner to clear the P0420 code from the ECM.
3. Start the engine and allow it to idle for several minutes to ensure the system is functioning correctly.