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 getting a signal that the temperature sensor for the exhaust system is too low. It's like a thermometer that isn't working right, so the car can't tell how hot the exhaust is.
The P042C code is triggered when the engine control module (ECM) detects a low voltage signal from the catalyst temperature sensor on bank 1, sensor 2.
The catalyst temperature sensor monitors the temperature of the catalytic converter to ensure it is operating efficiently. A low circuit reading indicates that the sensor is not sending the correct voltage signal to the ECM, which could be due to a faulty sensor, wiring issues, or a problem with the ECM itself.
• Check Engine Light is on
• Poor fuel economy
• Failed emissions test
• Faulty catalyst temperature sensor
• Damaged or corroded wiring or connectors
• ECM malfunction
ECM: Engine Control Module
Catalyst: A component in the exhaust system that reduces harmful emissions
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for damage or corrosion.
• Test the catalyst temperature sensor for proper operation.
• Replace the catalyst temperature sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Wrench set
$150 - $400
Moderate
• Toyota Camry
• Ford F-150
• Honda Accord
• Regularly inspect and maintain exhaust system components.
• Ensure proper engine tuning and maintenance.
• Use quality fuel to prevent sensor contamination.
Sensor Issue
• Address the issue promptly to avoid further damage.
• Consult a professional mechanic if unsure about repairs.
Check with the vehicle manufacturer for warranty coverage on emissions-related components.
This code has been associated with vehicles that have aging catalytic converters or sensors.
Moderate – While not immediately critical, driving with this issue can lead to increased emissions and potential damage over time.
Driving with a malfunctioning emissions system can lead to legal issues in areas with strict emissions regulations.
• Engine at operating temperature
• Vehicle at idle or cruising speed
The catalyst temperature sensor is located on the exhaust system, downstream of the catalytic converter on bank 1.
Q: Can I drive with a P042C code?
A: While you can drive with this code, it's best to address it soon to avoid potential damage and increased emissions.
Q: How do I reset the P042C code?
A: You can reset the code using an OBD-II scanner, but it's important to fix the underlying issue first.
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Universal · Digital multimeter
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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.