What it means
Catalyst temperature sensors 1 and 2 on bank 1 disagree by more than the allowed tolerance over a drive cycle.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Catalyst temperature sensors 1 and 2 monitor temperature at different points in the exhaust catalyst system on bank 1, the side containing cylinder 1. The control module sets P046A when their readings disagree more than expected over a drive cycle, which can point to a drifting sensor, circuit fault, or exhaust leak on that bank.
Common causes
Most likely first.
- One catalyst temperature sensor drifting or failing
- Open or short in a sensor circuit
- Corroded or loose sensor connector
- Exhaust leak affecting temperature readings
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
How to diagnose it
- Review freeze-frame data and compare bank 1 catalyst temperature sensor 1 and 2 live readings as the exhaust warms.
- Inspect both bank 1 sensor connectors and nearby wiring for corrosion, heat damage, loose terminals, or contact with the exhaust.
- Check the bank 1 exhaust joints around and between the sensor locations for leaks that could alter temperature readings.
- Test each bank 1 sensor circuit for opens or shorts and compare sensor response with the manufacturer's specification.
- If the sensors and circuits pass, investigate catalyst operation and exhaust conditions on bank 1 before replacing parts.
Common fixes
- Repair damaged or heat-affected wiring to a bank 1 catalyst temperature sensor.
- Clean or repair a loose or corroded connector at sensor 1 or sensor 2 on bank 1.
- Repair an exhaust leak affecting the bank 1 sensor readings.
- Replace the bank 1 sensor that fails its response or circuit checks.
Can I keep driving?
You can usually drive gently if there are no severe symptoms, but avoid hard acceleration and prolonged heavy loads until the temperature readings are checked. A catalyst or exhaust fault can worsen, raise emissions, or overheat exhaust components; stop if the exhaust glows or engine performance drops sharply.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.