Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car's system that cleans the exhaust isn't working as well as it should. It's like a filter that isn't catching all the dirt, so the car's computer is letting you know.
The code indicates that the heated catalyst on the first bank of the engine is not performing efficiently. This component helps reduce harmful emissions by converting them into less harmful substances.
The P0423 code is triggered when the Engine Control Module (ECM) detects that the heated catalyst's efficiency is below the required threshold on bank 1. This can be due to a malfunctioning catalyst or issues with the sensors monitoring its efficiency.
• Check Engine Light is on
• Increased emissions
• Possible decrease in fuel efficiency
• Faulty catalytic converter
• Damaged oxygen sensors
• Exhaust leaks
Catalytic Converter: A device that converts harmful emissions from the engine into less harmful substances.
Oxygen Sensor: A sensor that measures the amount of oxygen in the exhaust gases.
• Use an OBD-II scanner to confirm the code
• Inspect the catalytic converter for damage
• Check the oxygen sensors for proper operation
• Replace the catalytic converter
• Replace faulty oxygen sensors
• Repair any exhaust leaks
• OBD-II scanner
• Wrench set
• Multimeter
$500 - $2500
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regular maintenance of the exhaust system
• Use high-quality fuel
• Avoid short trips that don't allow the engine to reach operating temperature
Emissions Control
• Have the vehicle inspected by a professional
• Avoid driving for extended periods with this code active
Catalytic converters are often covered under the emissions warranty, which can last up to 8 years or 80,000 miles.
This code has been more common in vehicles with higher mileage or those that have not been regularly maintained.
Moderate – While not immediately dangerous, it should be addressed to ensure emissions compliance and prevent further damage.
Driving with a malfunctioning catalytic converter may not meet emissions standards and could result in a failed emissions test.
• Engine at normal operating temperature
• Vehicle driven under various conditions
The catalytic converter is located in the exhaust system, typically between the engine and the muffler.
Q: Can I drive with a P0423 code?
A: While you can drive with this code, it's not recommended to ignore it for long as it may lead to higher emissions and potential damage.
Q: How do I reset the P0423 code?
A: After repairs, you can reset the code using an OBD-II scanner, but ensure the issue is resolved to prevent it from returning.
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Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.