P2238

Code

Generic P — Powertrain

O2 Sensor Positive Current Control Circuit Low Bank 1 Sensor 1

Brand: Generic

Type: P — Powertrain

Views: UK: 37 EN: 84 RU: 52

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Open or high-resistance wiring between sensor and ECM
Corroded, loose or damaged sensor connector pins
Faulty oxygen (wideband) sensor (pump cell or internal electronics)
Faulty ECM/PCM current source or driver
Blown fuse or interrupted power/ground for sensor/ECM
Sensor contamination, exhaust leak, or mechanical damage reducing sensor function

Retrieve freeze frame and live data with a scan tool (bank 1 sensor 1 pump current / sensor voltage / fuel trims)
Visually inspect sensor wiring and connector for corrosion, damage, heat/abrasion, or pin push-out
Confirm relevant fuses and relays for sensor/ECM power are intact
Check for exhaust leaks near the upstream sensor that can affect readings
Wiggle test wiring while observing live data for intermittent changes

Typical narrowband zirconia voltage: ~0.1–0.9 V (for reference; code targets current control)
Wideband/pump sensor: ECU sources/sinks small control currents (usually milliamps) to maintain stoichiometry — expect measurable current pulses in live data when commanded
Heater circuit (if present): battery voltage (~11–14 V) when active; heater resistance per manufacturer specification
Expected behavior: when commanded rich/lean corrections are needed, pump current should move positive/negative from baseline (observe relative changes rather than absolute numbers)

Connect a scan tool and confirm the P2238 code, freeze frame, and live data for bank 1 sensor 1 (pump current, sensor voltage, fuel trims). Note whether code is current or historic.
Perform a visual inspection of the B1S1 sensor harness and connector. Repair any obvious damage, corrosion, or pin issues.
Verify power/ground to the sensor and continuity between the sensor connector and ECM pins. Repair any open/high-resistance circuits. Check related fuses and relays.
With connector attached or back-probed, monitor pump current and sensor signals while performing controlled engine conditions (idle, snap throttle). Look for expected response and for dropouts when manipulating wiring (wiggle test).
If wiring and supply/ground are good but current remains low, substitute a known-good compatible upstream wideband sensor, then re-test to see if the code clears.
If a replacement sensor does not clear the code, check ECM driver outputs for the pump/current control circuit and consult manufacturer technical service info for ECM bench tests or reprogramming. Replace ECM only after confirming all other causes eliminated.
After repair, clear codes and perform a drive cycle verifying the code does not return and that fuel trims and emissions-related parameters are normal.