P0057

What it means

P0057 means the engine control unit has detected a low voltage or low signal state in the heater control circuit of the heated oxygen sensor fitted downstream of the catalyst on Bank 2 (Sensor 2). The control unit switches the heater on and off to bring the sensor up to operating temperature quickly, and it monitors that circuit. If the voltage or current is lower than expected, usually a short to earth or excess current draw, it stores this code.

Symptoms

• Engine warning light on
• Usually no noticeable change in driveability
• Possible slight increase in emissions at the next test
• Other oxygen sensor or catalyst efficiency codes stored alongside
• Possible failed emissions or MOT check

Possible causes

• Internal short or fault in the Bank 2 Sensor 2 heater elementlikely
• Heater control wire chafed and shorted to earthlikely
• Damaged, corroded or water-contaminated sensor connectorpossible
• Exhaust heat damage to the sensor harness insulationpossible
• Blown fuse or fault in the heater power supply or relay, where fitted (varies by model)possible
• Fault in the heater driver inside the engine control unitrare

How to diagnose

1. Read all stored codes and freeze frame data, noting whether other oxygen sensor or catalyst codes are present, then confirm which side of the engine is Bank 2 for this model
2. Visually inspect the Bank 2 downstream sensor, its harness and connector for heat damage, chafing, corrosion and water ingress
3. Check the relevant fuse and any heater supply relay against the wiring diagram for this model
4. Unplug the sensor and measure heater element resistance, comparing it with the manufacturer's specification
5. Check the heater supply voltage at the connector with ignition on, and check the control wire for a short to earth with the connector unplugged
6. Check the control wire for continuity back to the control unit and for a short to earth or to other wires
7. Use a scan tool's bidirectional test, if supported, to command the heater and watch the circuit response
8. Clear the code and road test to confirm it does not return

How to fix

• Replace the Bank 2 Sensor 2 oxygen sensor if the heater element is shorted or out of specification
• Repair or replace the damaged heater control wiring and secure it away from hot exhaust parts
• Clean or replace a corroded or damaged connector and make sure the seals are intact
• Replace a blown fuse only after finding and fixing the cause of the overload
• Repair or replace the engine control unit only after all wiring and sensor faults have been ruled out

Can I keep driving?

Nearby codes

• P0056GenericHO2S Heater Control Circuit Bank 2 Sensor 2
• P0058GenericHO2S Heater Control Circuit High Bank 2 Sensor 2