Powertrain, generic (extended)

P2A3A O2 Sensor Positive Current Control Circuit High Bank 1 Sensor 3

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2A3A means the voltage on the pump-current (positive control) lead of probe number three, bank 1, sits above its expected level. The usual culprit is contact with a supply: the heater feed runs in the same harness and connector, and moisture or heat damage at the plug can bridge the two. An offset pump current would falsify the lambda value, so the controller stops trusting it. P2A3A is not described by any manufacturer in public sources; Ford handles a short to battery on its front IP wires under P0132 instead. P2A38 is the open-circuit fault, P2A39 the low one, P2A3D the high fault on the return. The engine normally runs as before, but the lamp comes on and diagnosis starts with voltage checks at the connector.

Likely causes

Pump-current wire touching the heater feed in harness or plug
Water or corrosion in the sensor connector under the car
Internal short between heater and pump cell of the probe

Symptoms

  • Check engine light after repeated detection
  • Sensor 3 reports an implausibly lean value

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–450
Time0.5–2.5 h

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

Parts involved

oxygen sensor b1s3wiring harnessecm

Related codes

P2A38P2A39P2A3DP22ADP0144

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