Powertrain, generic (extended)

P2256 O2 Sensor Negative Current Control Circuit High (Bank 2 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2256 means the negative current control line (reference ground) of the bank 2 upstream wide-band sensor reads too high, typically a short to battery or heater voltage. No manufacturer publicly documents P2256 with thresholds. Ford's OBD summaries send a short to battery on any wide-band sensor line to P0152 and reserve P2254 for the open line; VW's 2014 books also list only P2254 for this circuit. CARB requires fuel-control sensors to be checked for circuit continuity and out-of-range values, with separate codes where feasible. P2253 is the bank 1 counterpart, P2255 the low-side fault, P2254 the open circuit. A short to voltage can damage the sensor or the interface, so the wiring should be checked before a new sensor is fitted.

Likely causes

Reference ground wire shorted to heater supply or battery voltage
Internal short in the wide-band sensor
Fault in the sensor interface of the ECM

Symptoms

  • Check engine light
  • Higher fuel consumption
  • Repeat failure of a new sensor if the wiring short remains

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–450
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

oxygen sensor bank2 sensor1oxygen sensor wiringecm

Related codes

P2253P2254P2255P0152

References: law.cornell.edu, newtonnet.co.uk, fordservicecontent.com.