how to fix P0420 code on my Tesla Outback 5th Generation (2015-2019)

Subaru Outback 5th Generation (2015-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0420

3 min read

549 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 Subaru Outback (2015-2019). 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 inspection or repair.

Symptoms

•Check engine light illuminated
•Decreased fuel efficiency
•Rough idle or engine hesitation
•Failed emissions test
•Unusual exhaust smell (rotten egg odor)

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0420 and check for any related codes.
2
Inspect the exhaust system for any visible leaks or damage, particularly around the catalytic converter and exhaust manifold.
3
Check the oxygen sensor readings before and after the catalytic converter with a multimeter or scan tool to ensure they are functioning correctly.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter using an infrared thermometer to assess its efficiency.
5
Inspect the fuel trim readings to identify if the engine is running rich or lean, which could affect catalytic converter performance.
6
Verify the condition of the spark plugs and ignition system to ensure proper combustion.

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
•Infrared thermometer
•Wrench set

Parts Required

•Upstream oxygen sensor
•Downstream oxygen sensor
•Catalytic converter (if defective)

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0420 and check for any related codes.
2
Inspect the exhaust system for any visible leaks or damage, particularly around the catalytic converter and exhaust manifold.
3
Check the oxygen sensor readings before and after the catalytic converter with a multimeter or scan tool to ensure they are functioning correctly.
4
Measure the temperature difference between the inlet and outlet of the catalytic converter using an infrared thermometer to assess its efficiency.
5
Inspect the fuel trim readings to identify if the engine is running rich or lean, which could affect catalytic converter performance.
6
Verify the condition of the spark plugs and ignition system to ensure proper combustion.

Solution

1. Preparation

Gather tools and parts.
Disconnect the battery to prevent electrical shorts.
Allow the vehicle to cool if it has been recently driven.

2. Inspect and Replace Oxygen Sensors

Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
Unplug the electrical connectors from both sensors.
Use a socket wrench to remove the sensors from the exhaust system.
Apply anti-seize compound to the threads of the new oxygen sensors.
Install the new sensors, tightening them to the manufacturer’s specifications (usually around 30 ft-lbs).
Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

If the catalytic converter is confirmed faulty, locate the exhaust flange bolts connecting it to the exhaust system.
Remove any heat shields that may obstruct access.
Use a socket set to loosen and remove the flange bolts and any additional mounting hardware.
Carefully remove the old catalytic converter from the exhaust system.
Install the new catalytic converter, ensuring proper alignment and fit.
Reinstall the mounting hardware and heat shields, tightening them to manufacturer specifications.

4. Clear the Codes

Reconnect the battery.
Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
Start the engine and allow it to reach operating temperature.