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Error Code P0057 is defined as Heated Oxygen Sensor (HO2S) Heater Control Circuit Low, Bank 2, Sensor 2. Meaning, the PCM (powertrain control module) has detected a problem with Heated Oxygen Sensor’s heater element circuit, specifically low voltage issues on the Bank 2, Sensor 2.
Error Code P0057 is actually a generic error code, meaning it applies to all makes and models of vehicles (vehicles made since 1996 to present). Different vehicle manufacturers and models have slightly different steps for diagnosis and repair. In Nissan’s case for example, their description for the code is slightly different, which is “HO2S 2 Bank 2 –heater voltage low.
With that said, the job of the HO2S is the same for all makes and models of vehicles – to provide data for the PCM to use in reading the oxygen level of the exhaust system. The Bank 2, Sensor 2 refers to second sensor located at the back on Bank 2. The PCM gathers the data from the bank 2, 2 HO2S primarily to monitor catalytic converter’s efficiency. The heater element plays an integral role to this sensor.
The job of the PCM is to control the heater; the PCM warms the heater up to get the sensor to its appropriate operating temperature, ultimately allowing the engine to enter closed loop faster, with reduced emissions on cold startup. The PCM will continue to monitor the circuits for any signs of abnormal changes in the voltages, or in some cases, even the amperages. Depending on the make of the vehicle, the PCM controls the O2 sensor heater in two ways: first, the PCM controls the voltage feed to the heater, either directly or through the HO2S relay, with a supplied ground from the vehicle’s common ground. The second way is that, a fused 12V battery feed (B+) which feeds 12V to the heater element when the ignition is on, and the driver in the PCM controls the heater, which controls the ground of the heater circuit.
Knowing which type you have is extremely important, as the PCM activates the heater under various circumstances.
The Bank 2 is engine’s side which doesn’t contain the cylinder # 1.
Error Code P0057 is quite tricky, as there are no other noticeable symptoms aside from the activation of the Check Engine light. However, due to the fact that the sensor couldn’t be warmed up to its operating temperature in timely manner, the emissions will increase during cold start situations.
Possible causes for Error Code P0057 includes:
- Failed Bank 2, Sensor 2 heater element
- Physical damage to the HO2S
- Shorted to ground control circuit (or voltage feed, depending on the system)
- Failed PCM O2 sensor heater driver
How to Check
Diagnosis for this error code varies slightly from one manufacturer to another, but generally, it starts with a thorough inspection of the wiring that connects to the Bank 2 Sensor 2 Oxygen sensor. Accidents and road debris can easily cause problems to the connectors and wirings.
After confirming that there are no signs of damage to the connectors or wirings, mechanics will inspect the condition of the Bank 2, Sensor 2 oxygen sensor itself by disconnecting the sensor and using ohmmeter to measure the heater’s resistance. Again, the specifications for the heater vary depending on the manufacturer, but generally, it is around 4 to 5 ohms. If the tool says OL (out of limit) or INF (infinite) that means the heater has been burned out and should be replaced.
If the sensor and its components are all in good condition, the PCM is the next thing that should be checked. It should be unplugged and checked for resistance as well. The reading must be less than 1 ohm of resistance. A few ohms can mean a problem, and this can be caused by a broken wire (or partially broken inside its insulation). If so, then the wire must be replaced.
If everything is in good condition, but the error code remains, then there may be a problem with the PCM itself though a faulty PCM is quite rare.
How to Fix
As said earlier, the most common fix is to replace the troubled part that causes to trigger the code. The number one option you have however is to replace the Bank 2 Sensor 2 O2 sensor.
Next is repair or replacement of connectors or wiring.
Your last resort can be the replacement of the PCM itself.
One of the biggest mistakes people commit in fixing this trouble code is assuming quickly that the problem is in the O2 sensor and it should need replacement. Thus, it is crucial to conduct a thorough diagnosis.