What it means
The electric catalyst heater on bank 2 - used on hybrids and modern petrol cars to bring the catalyst above light-off temperature within seconds of cold start - reports that its supply voltage is outside the expected window. The heater cannot deliver the rated power, so cold-start emissions rise until the catalyst reaches light-off conventionally.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 2 catalyst heater electrically warms that bank's catalytic converter after a cold start. The control module monitors the heater supply voltage and sets this code when it is outside the expected range, potentially reducing heater output and increasing cold-start emissions.
Common causes
Most likely first.
- Heater supply voltage low or unstable
- DC/DC converter fault on heater rail
Symptoms
- Check engine light on
- Possible increase in cold-start emissions
How to diagnose it
- Save freeze-frame data and check whether the fault occurs during a cold start; review bank 2 heater command and reported supply voltage if available.
- With the system safely powered down as specified by the manufacturer, inspect bank 2 heater connectors and supply wiring for looseness, corrosion, damage, or heat marks.
- Check the bank 2 heater supply and ground connections for excessive voltage drop under the commanded load, using the manufacturer's procedure.
- Compare heater rail or DC/DC converter output with the manufacturer's specification while the bank 2 heater is commanded on.
- If supply and connections are sound, test the bank 2 heater and its control circuit according to the vehicle's service information.
Common fixes
- Clean and secure a loose or corroded bank 2 heater connection.
- Repair damaged bank 2 heater supply wiring or ground connections.
- Repair a faulty DC/DC converter or heater rail supply if testing confirms it.
- Replace the bank 2 catalyst heater if it fails the manufacturer's test.
Can I keep driving?
If the engine runs normally, this fault generally does not prevent driving, but cold-start emissions may rise and the vehicle may fail an emissions inspection. Arrange diagnosis soon, and use extra caution around high-voltage components on hybrid vehicles.
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.