P0056: HO2S Heater Control Circuit (Bank 2 Sensor 2)

What does P0056 mean?

The bank 2 rear oxygen-sensor heater circuit has a malfunction. This sensor is downstream of the catalyst on the bank opposite cylinder 1. Heater failure can prevent reliable emissions monitoring without causing obvious rough running, and it does not alone establish a failed catalytic converter.

Generic OBD-II definition: HO2S Heater Control Circuit (Bank 2 Sensor 2). Confirm applicability in your vehicle service information.

Common causes

• Open bank 2 downstream heater
• Missing power or return at the rear sensor
• Corroded or broken heater harness

Symptoms

• Check engine light
• Usually little or no change in drivability
• Catalyst monitor may not complete

Diagnostic focus

This is bank 2 sensor 2, downstream of that bank's catalyst. Some reference headings mislabel it as bank 1; identify the actual bank from the service diagram.

Can I keep driving with P0056?

Severity: Low If the engine runs normally and the light is steady, arrange emissions-system diagnosis. Stop for a flashing light or severe roughness; those symptoms need separate urgent attention.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

• Allow the exhaust to cool before inspecting wiring
• Verify the bank 2 rear sensor heater supply and continuity before considering catalyst repairs.
• Repair wiring or replace the correct sensor only when the fault is confirmed

Sources & review

• OBD-Codes.com: P0056
• TroubleCodes.net: generic code definitions

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.