Powertrain, generic (extended)

P2A05 O2 Sensor Circuit Range/Performance Bank 2 Sensor 3

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2A05 refers to the third oxygen sensor on bank 2, mounted behind a further converter or aftertreatment stage of a V or flat engine. No manufacturer documents this code publicly. The nearest documented case is its bank-1 counterpart: GM's 2025 diesel tables compare the oxygen value of sensor 3 with that of sensor 2 at full load and set P2A02 when the gap exceeds 6 % in 120 of 240 samples. Ford's downstream checks show the other route into a range fault, a reading that sinks below −0.2 V, which Ford, however, files only for sensor 2. CARB requires downstream sensors to stay good enough for the monitors that rely on them. An implausible sensor 3 goes largely unnoticed while driving, but the converter or aftertreatment check of bank 2 cannot finish.

Likely causes

Third sensor on bank 2 drifting or slow with age
Exhaust leak in the pipe between sensor 2 and sensor 3
Damaged or heat-affected wiring under the vehicle

Symptoms

  • Check engine light on
  • Readiness for the catalyst or aftertreatment monitor missing
  • Usually no change in driving behaviour

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–500
Time0.5–2 h

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

Parts involved

oxygen sensorexhaust pipe

Related codes

P0162P0165P2276P2A02P2A04P2A11

References: law.cornell.edu, gsi.ext.gm.com, newtonnet.co.uk.