Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is having trouble reading the temperature from a sensor that checks how hot the exhaust is getting after it leaves the engine. It's like a thermometer that isn't working right.
The P042B code indicates that the engine control module (ECM) has detected a problem with the range or performance of the catalyst temperature sensor located on bank 1, sensor 2.
The catalyst temperature sensor is responsible for monitoring the temperature of the catalytic converter. This sensor helps ensure that the catalytic converter is operating within the optimal temperature range. If the ECM detects that the sensor's readings are outside the expected range or not performing as expected, it triggers the P042B code.
• Check Engine Light is on
• Possible decrease in fuel efficiency
• Potential increase in emissions
• Faulty catalyst temperature sensor
• Wiring issues or poor electrical connections
• Exhaust leaks affecting sensor readings
Catalyst: A component in the exhaust system that reduces harmful emissions.
ECM: Engine Control Module, the computer that manages engine functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connections to the sensor.
• Test the sensor for proper operation.
• Replace the faulty catalyst temperature sensor.
• Repair or replace damaged wiring or connectors.
• Fix any exhaust leaks.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Toyota Camry
• Ford F-150
• Honda Accord
• Regular maintenance and inspection of exhaust system
• Ensure proper sensor installation
• Address exhaust leaks promptly
Sensor Issue
• Have the vehicle inspected by a professional mechanic.
• Avoid driving the vehicle for extended periods to prevent further damage.
Check with your vehicle manufacturer for warranty coverage on emissions-related components.
This code has been associated with vehicles that have higher mileage or those that have experienced exhaust system issues.
Moderate – While the vehicle may still be drivable, it is important to address the issue to prevent potential damage to the catalytic converter.
Driving with a faulty catalyst temperature sensor can lead to increased emissions, which may not meet legal standards.
• Engine at operating temperature
• Vehicle running at idle
The catalyst temperature sensor is located downstream of the catalytic converter on bank 1.
Q: Can I drive with a P042B code?
A: While you can drive with this code, it's best to get it checked out soon to avoid potential damage to the catalytic converter.
Q: How do I know if the sensor is bad?
A: A mechanic can test the sensor with a multimeter to see if it is functioning properly.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
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 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.