Failed heater element inside the bank 2 sensor 2 oxygen sensor; Damaged, chafed or melted wiring to the sensor, often near the exhaust; Corroded, loose or contaminated connector at the sensor; Blown fuse or fault in the heater power supply feed; Faulty relay in the heater supply circuit on models that use one; Fault in the engine control unit heater driver.

P0056

HO2S Heater Control Circuit Bank 2 Sensor 2.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
56: FaultThe specific fault in that area

What it means

P0056 is the generic code for a fault in the heater control circuit of the heated oxygen sensor on bank 2, sensor 2. This is the sensor downstream of the catalytic converter on the side of the engine opposite cylinder number one. The engine control unit monitors the heater circuit and set the code because the current or voltage in the circuit was outside the expected range.

Symptoms

Engine warning light on
Usually no noticeable change in how the car drives
Possible slight increase in fuel consumption in some cases
Failed emissions test or readiness monitors not completing
Other oxygen sensor or catalyst efficiency codes stored alongside

Possible causes

Failed heater element inside the bank 2 sensor 2 oxygen sensorlikely
Damaged, chafed or melted wiring to the sensor, often near the exhaustlikely
Corroded, loose or contaminated connector at the sensorlikely
Blown fuse or fault in the heater power supply feedpossible
Faulty relay in the heater supply circuit on models that use onepossible
Fault in the engine control unit heater driverrare

How to diagnose

Read all stored codes and freeze frame data, and note any other oxygen sensor or misfire codes
Confirm which side is bank 2 and that the correct sensor is being tested, as layout depends on the engine
Visually inspect the sensor wiring and connector for heat damage, chafing, corrosion and water ingress
Check the relevant fuse and any heater relay, following the wiring diagram for the model
Measure the heater element resistance at the sensor and compare it with the manufacturer specification
With the connector unplugged, check for battery supply and a good earth or control signal on the heater circuit as per the wiring diagram
Check the wiring between the sensor and control unit for open circuits or shorts to earth or voltage
Clear the code and road test, then recheck that the code does not return and the monitors complete

How to fix

Replace the bank 2 sensor 2 oxygen sensor if the heater element is open circuit or out of specification
Repair or replace damaged wiring and secure it away from hot exhaust parts
Clean or replace corroded or damaged connector terminals
Replace a blown fuse after finding the cause of the failure, or a faulty relay
Repair the supply or control circuit fault found during testing
Have the control unit tested and repaired or replaced only after all wiring and sensor checks pass

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects drivability. Do not leave it too long, because it can cause an emissions test failure and may mask other faults.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.