The P2256: O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1 code refers to a problem where the voltage in the negative current control circuit of the oxygen (O2) sensor for Bank 2 Sensor 1 is higher than expected. This condition can indicate a malfunction that prevents the O2 sensor from properly monitoring the exhaust gases, which leads to incorrect air-fuel mixture adjustments and affects engine performance and emissions. The root causes may include faulty wiring, a malfunctioning sensor, or connector problems.
P2256 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P2256: O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1 |
| Is it serious? | Yes, as a high voltage condition can lead to incorrect O2 sensor readings, which affects fuel efficiency, engine performance, and emissions. |
| Possible causes | – High voltage in O2 sensor negative current control circuit for Bank 2 Sensor 1 – Faulty O2 sensor – Wiring issues – Connector problems |
| How to diagnose? | – Measure voltage in the O2 sensor negative current control circuit for Bank 2 Sensor 1 – Test the sensor for proper operation – Inspect wiring and connectors for faults |
P2256 Meaning
The P2256: O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1 code indicates that there is an abnormally high voltage in the negative current control circuit of the O2 sensor located in Bank 2 Sensor 1. This elevated voltage may be due to an issue with the sensor itself, poor wiring, or a connection problem. Such a condition can prevent the sensor from correctly measuring the exhaust’s oxygen levels, leading to improper air-fuel mixture adjustments, which may impact engine performance and increase emissions.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to determine if there are any additional related codes. Other codes might help identify whether this is an isolated issue or part of a larger fault affecting the system. | OBD-II Scanner |
| Measure Voltage in the O2 Sensor Negative Current Control Circuit | Use a multimeter to measure the voltage in the negative current control circuit for Bank 2 Sensor 1. Compare the readings with the manufacturer’s specifications. If the voltage is higher than expected, there could be a short circuit, poor grounding, or an issue with the sensor itself. | Multimeter, Vehicle Service Manual |
| Test the Sensor for Proper Operation | Use a diagnostic scanner to evaluate the O2 sensor. If the sensor is not providing appropriate readings or responds incorrectly to changes, it may need to be replaced to correct the high voltage issue. | Diagnostic Scanner, Multimeter |
| Inspect Wiring and Connectors for Faults | Visually inspect the wiring and connectors associated with the O2 sensor. Look for damaged insulation, melted wires, or loose or corroded connectors, which could cause increased resistance and lead to high voltage in the circuit. Repair or replace any damaged components. | Flashlight, Safety Gloves |
| Check the Sensor Connector Condition | Inspect the sensor connector for bent pins, poor fit, or corrosion. A bad connection could lead to a high voltage condition in the circuit. Make sure the connector is properly aligned and securely attached. | Flashlight |
| Clear the Code and Test Drive | After completing all necessary repairs, use an OBD-II scanner to clear the code. Conduct a test drive while monitoring the sensor’s performance to verify that the negative current control voltage is now within the correct range and the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | After the test drive, re-scan the vehicle using the OBD-II scanner to ensure that the P2256 code has not returned. If the code persists, further diagnostics may be required to identify underlying issues with the circuit or sensor. | OBD-II Scanner |
Free PDF: How to choose OBD2 scanner
I’ve made you a free PDF to choose the OBD2 scanner in 5 minutes.
✅ Which OBD2 scanner is best?
✅ Which type should you get (DIY, Pro, Hobby)
✅ What is the best scanner for the exact brand/feature (e.g best for BMW)
✅ How to get a Bi-Directional tool for as cheap as $40
✅ Discount coupons for scanners
PDF is 100% free and it is designed to help you pick a scanner in less than a few minutes! Not a boring 50-page guide.
Just tell me where to send it.
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)