What Does P2256 Mean?
The PCM has detected that the negative current control circuit voltage for Bank 2 Sensor 1 oxygen sensor is above the expected range. This indicates excessive voltage or an open circuit in the sensor's pumping cell control.
Common Causes
35%
Open circuit in oxygen sensor wiring harness or connector
30%
Failed oxygen sensor with internal open circuit
20%
Corroded or loose connector terminals creating high resistance
10%
Broken or damaged wiring from road debris or heat damage
5%
PCM control circuit driver failure
Diagnostic Steps
1
Step 1: Inspect oxygen sensor wiring harness for cuts, abrasion, or heat damage along entire length
2
Step 2: Check continuity of negative current control circuit from sensor connector to PCM
3
Step 3: Verify connector terminals are fully seated and not backed out or corroded
4
Step 4: Monitor voltage on control circuit with key on, engine off (should be approximately 0.4-0.5V)
5
Step 5: Replace oxygen sensor if all wiring and connections test normal
Estimated Repair Cost
$200 - $550
Parts + labor, varies by vehicle and location
The PCM has detected that the negative current control circuit voltage for Bank 2 Sensor 1 oxygen sensor is above the expected range. This indicates excessive voltage or an open circuit in the sensor's pumping cell control.
The most common cause of P2256 (O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1) is: Open circuit in oxygen sensor wiring harness or connector
Typical repair costs for P2256 range from $200 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but may run lean causing rough idle and potential engine damage. Repair promptly to avoid catalytic converter damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2256 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System / Emissions Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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