P042C
Catalyst Temperature Sensor Circuit Low Bank 1 Sensor 2
Catalyst temperature sensor / emissions
Generic OBD-II
Medium
What it means
P042C means the signal from the bank 1, sensor 2 catalyst temperature sensor is reading below its valid range. This sensor monitors the catalytic converter's temperature so the computer can protect it and run its emissions checks. A low signal almost always points to the sensor, its wiring, or a poor connection rather than an engine problem, so the car generally starts and drives normally.
Medium
Can I keep driving? You can keep driving. This is a sensor-circuit fault that mainly affects emissions monitoring, not how the engine starts or runs.
Common symptoms
What you'll notice
- Check-engine light on
- Usually no noticeable change in how the car drives
- Catalyst-related emissions monitors may not complete
- Possible failed emissions readiness check
Common causes
Most likely first
- Faulty catalyst temperature sensor (bank 1, sensor 2) reading lowLikely
- Signal wire shorted to ground or an open in the circuitCommon
- Corroded or loose sensor connectorCommon
- Damaged wiring near the hot exhaustLess often
- Failed ECM (rare — check the sensor and wiring first)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code is on the bank 1 sensor 2 catalyst temperature sensor.
- Inspect the sensor connector and harness for a short to ground, corrosion, or heat damage.
- Check the sensor's reference and ground circuits back to the ECM.
- Measure the sensor's resistance/output and compare against spec at a known temperature.
- Replace the catalyst temperature sensor if it reads out of range, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P042C?+
Yes. It's a temperature-sensor circuit fault that doesn't affect starting or normal running. Repair it so the catalyst monitors work and the car can pass inspection.
Can I just clear P042C?+
It will return unless the sensor or its wiring is repaired.
Related codes
Often seen with P042C
Read & clear P042C yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX