O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1
The P2256 code indicates that the Powertrain Control Module (PCM) has detected a high voltage or resistance in the negative current control circuit of the oxygen sensor located on Bank 2, Sensor 1 (upstream of the catalytic converter). This circuit is responsible for regulating the sensor's heater current. A high condition suggests an open or short to voltage in the wiring, a faulty sensor, or a PCM issue. This can lead to inaccurate air-fuel ratio readings, affecting engine performance and emissions.
01. Most Common Causes
- Faulty oxygen sensor (Bank 2 Sensor 1)
- Open or shorted wiring in the sensor circuit
- Corroded or damaged connector
- Blown fuse for the O2 sensor heater circuit
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation
- Failed emissions test
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and note freeze frame data.
Step 2: Visually inspect the O2 sensor wiring and connector for damage, corrosion, or loose connections.
Step 3: Using a multimeter, check the negative current control circuit for continuity and shorts to ground or voltage.
Step 4: Test the O2 sensor heater resistance and compare to manufacturer specifications.
Step 5: If wiring and sensor check out, test the PCM output for the heater control circuit.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances, but it may cause poor fuel economy and increased emissions. Prolonged driving could damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for diagnosis and sensor replacement, plus parts cost ($50-$200 for the sensor).