What it means
The control or supply line to the electric catalyst heater on bank 1 is shorted to ground or measures below the expected voltage when the heater is commanded on.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The bank 1 catalyst heater circuit powers or controls the heater for the catalytic converter on bank 1. When the heater is commanded on, the control module detects circuit voltage below the expected level; a short to ground, an internally shorted heater, or a poor connection can cause this low reading.
Common causes
Most likely first.
- Control line shorted to ground
- Heater element internally shorted
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Possible increase in cold-start emissions
How to diagnose it
- Save freeze-frame data and confirm when the bank 1 heater was commanded on and the low-circuit fault was detected.
- Power down the system as directed by the manufacturer, then inspect bank 1 heater wiring and connector pins for damage, corrosion, moisture, or contact with ground.
- Check the bank 1 heater circuit for a short to ground using the manufacturer's isolation and test procedure.
- Measure voltage drop across the bank 1 heater connections under the specified test conditions and compare with the manufacturer's specification.
- If the wiring and connectors pass, test the bank 1 heater element for an internal short using the manufacturer's procedure.
Common fixes
- Clean and secure corroded or loose bank 1 heater connector pins.
- Repair a bank 1 heater control or supply wire shorted to ground.
- Repair damaged bank 1 heater wiring.
- Replace the bank 1 heater if it is internally shorted.
Can I keep driving?
This fault usually affects cold-start emissions rather than normal engine operation, but the warning light may remain on and the vehicle may fail an emissions inspection. Arrange diagnosis soon; take extra care 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.