What it means
Catalyst temperature sensor at bank 1 sensor 1 above upper plausibility — open signal or short to B+.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 sensor 1 catalyst temperature sensor reports temperature near the upstream side of the catalytic converter. P0428 sets when the control module sees a signal above its expected range, which can happen if the signal circuit is open or shorted to battery voltage and leaves temperature monitoring unreliable.
Common causes
Most likely first.
- Open signal line
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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
- Record freeze-frame data and check whether the bank 1 sensor 1 temperature PID is pinned high or implausible under the recorded conditions.
- Inspect the sensor connector for corrosion, loose contacts, or a terminal that has backed out.
- Trace the sensor wiring for breaks, heat damage, or a pinched section that could contact a powered wire.
- Check for an open in the signal wire and for unintended voltage on the signal circuit, using the manufacturer's wiring information and specification.
- If wiring and connector checks pass, test the sensor itself and then the control-module circuit before condemning either component.
Common fixes
- Reconnect the sensor plug and correct loose or damaged terminals.
- Repair an open signal wire or a section pinched against a power source.
- Replace a corroded connector or damaged harness section.
- Replace the bank 1 sensor 1 temperature sensor if it fails specification with sound wiring.
Can I keep driving?
Short, gentle trips are generally reasonable if the vehicle runs normally, but avoid heavy loads if it hesitates, smells of sulfur, or loses power. The fault can compromise emissions monitoring and lead to an inspection failure.
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.