FixItFor.Us
P codepowertrainMedium severity

P2238O2 Sensor Positive Current Control Circuit Low (Bank 1 Sensor 1)

The pumping-current control circuit of the Bank 1 upstream wideband air-fuel ratio sensor is reading lower voltage than expected, usually from a short to ground or a failing sensor.

Definition

Wideband air-fuel ratio sensors measure mixture by having the PCM drive a small pumping current through the sensor's pump cell; the PCM monitors the positive current control (IP+) circuit and sets P2238 when its voltage falls below the calibrated threshold, indicating a short to ground or open in that circuit for Bank 1 Sensor 1. Because this is the primary fuel-control sensor, the PCM typically defaults to open-loop or fixed fuel trim for that bank. Expect an illuminated MIL, reduced fuel economy, possible hesitation or rich/lean drift, and an emissions-test failure.

Common causes

  • Failed wideband air-fuel ratio sensor (aged or contaminated pump cell)
  • IP+ signal wire shorted to ground from harness chafing
  • Corroded, bent, or backed-out terminals in the sensor connector
  • Open circuit in the pumping current wire between sensor and PCM
  • Faulty PCM air-fuel sensor driver circuit (least common)

Common misdiagnoses

  • Conventional narrowband O2 sensor logic applied and a cheap universal sensor installed, causing repeat codes
  • Catalytic converter replaced for fuel-trim symptoms
  • MAF sensor replaced for lean/rich drift caused by the AFR sensor circuit
  • Downstream O2 sensor replaced instead of the upstream AFR sensor

Troubleshooting steps

  1. 1.Confirm the sensor type and read scan data

    Verify the vehicle uses a wideband AFR sensor at B1S1 and check whether the equivalence ratio/lambda PID is stuck at a fixed value, which indicates the PCM has stopped trusting the sensor.

  2. 2.Inspect the sensor connector and pigtail

    Look for green corrosion, spread terminals, and wiring rubbed through near the exhaust manifold or heat shields.

  3. 3.Test the IP+ circuit for shorts and continuity

    With sensor and PCM disconnected, verify near-zero ohms end to end on the pumping current wire and no continuity to chassis ground or other pins.

  4. 4.Compare sensor pin resistances to specification

    Check the sensor's internal cell resistances against the service manual values; out-of-range readings condemn the sensor.

  5. 5.Replace with an OEM or OE-supplier sensor and verify

    Wideband sensors are calibration-specific — install the correct part number, clear codes, and confirm closed-loop operation and normal short-term fuel trim resumes.

Related codes