P2256: O2 Sensor Negative Current Control Circuit High Bank 2 Sensor 1
What to do
Expect worse economy and reduced power. Ask for resistance rather than continuity to be measured on the circuit. And as with every code in this family, do not accept a switching-voltage test as evidence this sensor has failed — it is the wrong test for this kind of sensor.
What this code means
The bank 2 negative current control circuit reads above its valid range — a short to supply, or a return path with developed resistance. Measure resistance rather than continuity, for the reason given at P2253.
This closes the twenty-code wideband family. The single most useful thing carried across all of it is at P2237: these codes only exist on vehicles with wideband upstream sensors, and the conventional switching-voltage test that works on a narrowband sensor will report a healthy one as dead.
Likely causes
Start here
- Wiring shorted to voltage · moderate
- High resistance in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
- Faulty oxygen sensor · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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