Code P0057: Heated Oxygen Sensor Heater Control Circuit Low (B2S2)
The generic diagnostic trouble code P0057 indicates a low voltage problem in the heater control circuit for Heated Oxygen Sensor (HO2S) #2 of Bank 2. At Nissan, it is often labeled “Heated Oxygen Sensor (HO2S) 2, Bank 2 – Heater Voltage Low”. This is a generic code and applies to most vehicles from 1996 onwards.
Function of the HO2S and its Heater
The Heated Oxygen Sensor (HO2S) measures the oxygen content in the exhaust gases. The sensor designated “Bank 2, Sensor 2” (B2S2) is located after the catalytic converter. Its primary role is to monitor the efficiency of the catalyst.
An integrated heating element allows the sensor to quickly reach its optimal operating temperature. This is crucial for reducing emissions during cold starts and enabling the engine to run in “closed loop” mode sooner. The Powertrain Control Module (PCM) controls this heater. There are two main configurations:
- The PCM directly controls the voltage supply (12V), and the ground is provided by the vehicle chassis.
- The voltage supply (12V) is constant (battery), and the PCM controls the circuit by managing the ground via an internal transistor (driver).
The P0057 code triggers when the PCM detects an abnormally low voltage in this control circuit. Bank 2 refers to the side of the engine that does not contain cylinder number 1.
Symptoms of Code P0057
Symptoms are often subtle:
- Illumination of the Malfunction Indicator Lamp (MIL) on the dashboard.
- Frequent absence of noticeable driving symptoms.
- In rare cases, an increase in pollutant emissions or a slight decrease in fuel consumption.
Possible Causes of the Fault
Several components can cause the P0057 code:
- Failure of the heating element in the HO2S B2S2 sensor (most common cause).
- Damaged wiring: cut, chafed, melted, or shorted-to-ground wires.
- Oxidized, corroded, or loose connector at the sensor or PCM.
- Failure of the heater driver inside the PCM (internal fault).
- Faulty voltage supply (blown fuse or open circuit) for systems where the PCM controls the +12V.
Diagnosis and Solutions for Resolving P0057
Before replacing parts, follow these diagnostic steps:
- Visual Inspection: Carefully inspect the Bank 2 HO2S sensor, its connector, and the wiring harness. Look for any signs of physical damage, burning, or corrosion. Ensure the wiring is properly routed and away from hot exhaust parts.
- Electrical Test:
- With the ignition off, disconnect the HO2S sensor connector.
- Depending on your vehicle’s configuration, use a multimeter to check for +12V at the connector (with ignition on) or for ground continuity.
- Test the resistance of the sensor’s heating element (refer to manufacturer specifications). An infinite resistance (open circuit) or zero resistance (short circuit) confirms sensor failure.
- Control Circuit Test: If the power and ground are correct, check the integrity of the control wire between the sensor and the PCM for a possible short to ground.
The most common solution is replacing the faulty oxygen sensor for Bank 2, Sensor 2. If the control circuit is shorted, wiring repair is necessary. An internal PCM failure is rare but possible.
Call to Action
Diagnosing a P0057 code requires a multimeter and knowledge of automotive electricity. If you are not comfortable with these procedures, consult a professional mechanic for an accurate diagnosis. Ignoring this code can, in the long term, damage the catalytic converter, a very expensive component.