Powertrain, generic (extended)

P2AC6 Intake Air O2 Sensor Reference Voltage Circuit High Bank 2

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2AC6 indicates an excessive reference voltage on the intake oxygen sensor serving bank 2, as happens when the reference wire touches a supply or battery feed, when the sensor ground is open or when moisture bridges the connector pins. Like the other bank 2 codes of this group, it is not documented by any manufacturer; the basis is CARB's general rule that input components must be checked for out-of-range values in both directions. Ford's patents on intake oxygen sensing describe the sensor element and the reference-voltage operation that this check protects. Before replacing the sensor, unplug it and measure the reference lead against ground and against battery voltage with the ignition on. P2AC5 is the low side, P2AC2 the bank 1 counterpart.

Likely causes

Reference wire of the bank 2 sensor shorted to a supply or battery feed
Open sensor ground
Moisture bridging pins in the connector

Symptoms

  • Check engine light on
  • EGR on bank 2 reduced, NOx may rise

Repair estimate

DifficultyMediumDIY possible
Parts and labour€0–350
Time0.3–2 h

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

Parts involved

intake air o2 sensor b2wiring harnessecm

Related codes

P2AC3P2AC4P2AC5P2AC2

References: patents.google.com, patents.google.com, law.cornell.edu.