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P codepowertrainMedium severity

P2629O2 Sensor Pumping Current Trim Circuit/Open (Bank 2 Sensor 1)

An open or fault has been detected in the pumping current trim (calibration) circuit of the upstream wideband air-fuel ratio sensor on Bank 2.

Definition

The ECM uses a pumping current trim resistor, typically integrated into the sensor connector, to calibrate the wideband air-fuel ratio sensor's pumping current for accurate lambda measurement. P2629 sets when the Bank 2 Sensor 1 trim circuit reads open or out of range. The MIL turns on and fuel control on Bank 2 loses accuracy, which can show up as a fuel trim split between banks, slightly degraded fuel economy, and an emissions-test failure, usually without dramatic driveability complaints.

Common causes

  • Corroded, water-intruded, or heat-damaged Bank 2 sensor connector containing the trim resistor
  • Open wiring in the pumping current trim circuit
  • Failed Bank 2 air-fuel ratio sensor
  • Poor terminal tension or a backed-out pin at the sensor or ECM connector
  • ECM fault (rare)

Common misdiagnoses

  • Bank 1 sensor replaced due to bank confusion
  • Downstream O2 sensor replaced instead of the upstream AFR sensor
  • Sensor replaced repeatedly when the harness or connector was at fault
  • Fuel system components replaced for a bank-to-bank trim difference

Troubleshooting steps

  1. 1.Confirm which sensor is Bank 2 Sensor 1

    Verify bank identification for the specific engine (Bank 2 is the bank opposite cylinder 1) so you do not test or replace the wrong sensor.

  2. 2.Inspect the sensor connector

    Check for corrosion, moisture, or melted plastic in the connector body, since the calibration resistor inside it is part of the monitored circuit.

  3. 3.Check the harness for damage

    Look for exhaust-heat damage and chafing along the Bank 2 sensor pigtail and harness run, which often differs in routing from Bank 1.

  4. 4.Verify circuit integrity to the ECM

    With the connectors apart, test the trim line and related sensor wires for continuity and shorts using the wiring diagram pinout.

  5. 5.Replace the sensor and validate

    If wiring passes, install a new OE-quality AFR sensor, clear codes, and confirm Bank 2 lambda tracks Bank 1 under matched conditions.

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