P0427: Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 1 — what it means, the affected system and what to check before replacing parts.
Meaning, symptoms, causes and checks
Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 1. Basic catalogue definition; diagnostic details have not yet been reviewed.
Affected system: Powertrain
Symptoms
- Check Engine light illumination
- Increased exhaust emissions
- Noticeable decrease in fuel economy
- Possible failure of emissions test
- Engine running in fail-safe mode
Possible causes
- Faulty catalyst temperature sensor
- Damaged or shorted sensor wiring
- Corroded or loose electrical connectors
- Blown fuse in the sensor circuit
- Internal engine control module (ECU) fault
What to check
- Inspect the sensor connector for signs of corrosion or moisture
- Test the wiring harness for continuity and short circuits to ground
- Verify the voltage supply at the sensor connector using a multimeter
- Compare the sensor resistance values against manufacturer specifications
- Check the fuse box for any blown fuses related to the exhaust system
Also written as: P0427-00, P042700, PO427 (some scan tools add the fault-type byte, e.g. -00).