P0423

Heated Catalyst Efficiency Below Threshold Bank 1

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$167–556 (est.)

Symptoms

Increased fuel consumption
Reduced engine power
Sulfur smell from exhaust pipe
Check Engine Light Is On

Causes

Worn or damaged catalytic converter
Malfunction of oxygen sensors
Leaks in the exhaust system
Incorrect fuel/air mixture (lean/rich)
Problems with the ignition system (misfire)

How to Fix

Check the condition of the catalytic converter
Test oxygen sensors (upper and lower)
Check the exhaust system for leaks
Diagnose the ignition system and fuel system
If necessary, replace the catalyst or other faulty components

Related codes

P0420 P0430 P0300