how to diagnose a bad catalytic converter on Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather tools: OBD-II scanner, exhaust back pressure gauge, infrared thermometer, socket set, jack stands.
• Ensure the vehicle is parked on a flat surface and the engine is cool.

2. Scan for Error Codes

• Connect the OBD-II scanner to the vehicle’s diagnostic port.
• Turn the ignition to the "ON" position without starting the engine.
• Record any trouble codes related to the catalytic converter (e.g., P0420).

3. Check Exhaust Back Pressure

• Locate the exhaust manifold or any accessible point before the catalytic converter.
• Use the exhaust back pressure gauge; insert it into the exhaust system and start the engine.
• Observe the pressure reading; if it exceeds 2.5 psi, there may be a blockage.

4. Visual Inspection

• Safely raise the vehicle using jack stands and remove any shields obstructing access to the catalytic converter.
• Check for physical damage or corrosion on the catalytic converter casing.
• Inspect surrounding pipes for leaks or damage.

5. Temperature Test

• Start the engine and allow it to reach operating temperature.
• Use an infrared thermometer to measure the temperature at the inlet and outlet of the catalytic converter.
• Compare the readings; a difference greater than 100°F suggests that the catalytic converter may not be functioning properly.

6. Fuel Trim Test

• Use the OBD-II scanner to monitor live data for fuel trims.
• Check short-term and long-term fuel trims; abnormal values (greater than ±10%) can indicate a catalytic converter issue.

7. Decision

• If diagnostics confirm catalytic converter failure, proceed with replacement based on the severity of the findings.