Catalyst Temperature Sensor Range/Performance (Bank 1)
What does P0426 mean?
The P0426 code means the vehicle's onboard diagnostic system has detected: Catalyst Temperature Sensor Range/Performance (Bank 1). This is a low severity code.
Common Symptoms
- Check Engine Light illuminated
- No drivability symptoms
- Catalyst monitoring disabled by ECM
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Degraded catalyst temperature sensor with slow response Very High
- Soot or carbon buildup on the sensor tip High
- Intermittent wiring connection to the sensor Moderate
- Exhaust leak near the sensor affecting readings Low
Step-by-Step Diagnostic Procedure
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Monitor catalyst temperature sensor readings during warm-up -- they should rise steadily and match expected values
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Compare sensor readings to an infrared thermometer aimed at the exhaust pipe near the sensor
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Inspect the sensor for heavy soot or carbon buildup
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Check for exhaust leaks near the sensor location
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Replace the sensor if response time is slow or readings are erratic
Frequently Asked Questions
Can I drive with code P0426?
Yes. The sensor is not reading correctly but this does not impact how the engine runs. The ECM disables catalyst temperature monitoring until repaired.
Can I clean the catalyst temperature sensor?
In some cases, carefully cleaning soot from the sensor tip can restore proper readings. However, if the internal thermistor element has degraded, replacement is necessary.
How do I test the catalyst temperature sensor?
Measure resistance at room temperature and compare to the manufacturer specification. Then warm it with a heat gun and verify resistance changes appropriately. Slow or no change indicates a bad sensor.