Catalyst Temperature Sensor (Bank 1)
The P0425 code means the vehicle's onboard diagnostic system has detected: Catalyst Temperature Sensor (Bank 1). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $80 - $300 (parts and labor)
Reads enhanced codes and shows real-time O2 sensor data. Verify the cat is actually bad before dropping $1,000+ on a replacement.
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Common Symptoms
- Check Engine Light illuminated
- No noticeable drivability issues
- ECM cannot monitor catalyst temperature
- Failed emissions test
Probable Causes (Ranked by Likelihood)
- Faulty catalyst temperature sensor Very High
- Open or shorted sensor wiring High
- Corroded sensor connector Moderate
- ECM sensor input circuit fault Low
Step-by-Step Diagnostic Procedure
-
Read catalyst temperature PID on a scan tool -- it should increase as the engine warms up
-
Inspect the catalyst temperature sensor connector for corrosion or damage
-
Measure sensor resistance at various temperatures and compare to specifications
-
Check wiring continuity from sensor to ECM
-
Replace the sensor if readings are out of specification
Frequently Asked Questions
Can I drive with code P0425?
Yes. The catalyst temperature sensor monitors converter health but does not affect engine performance. The ECM may disable catalyst monitoring until the sensor is repaired.
Where is the catalyst temperature sensor?
It is typically threaded into the exhaust pipe near the catalytic converter, either before or after the converter depending on the vehicle design.
Is the catalyst temperature sensor the same as an oxygen sensor?
No. The catalyst temperature sensor is a thermistor that measures exhaust temperature, while an oxygen sensor measures exhaust oxygen content. They serve different monitoring purposes.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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