P2626

Code

Generic P — Powertrain

O2 Sensor Pumping Current Trim Circuit/Open Bank 1 Sensor 1

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 60 RU: 84

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Page language: EN

Causes

Open or shorted wiring/connectors between sensor and PCM
Failed wideband/UEGO oxygen sensor (pump cell or internal electronics)
Faulty sensor heater or heater circuit (affects sensor operation)
Poor ground or intermittent connector contact
Exhaust leaks near the sensor or damaged sensor harness
PCM fault or internal driver failure (less common)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Poor fuel economy or increased emissions
Rough idle, hesitation or drivability complaints under some conditions
Failed emissions test or incorrect short-term/long-term fuel trim behavior
Possible difficulty starting if heater is inoperative in cold conditions

What to check

Read stored freeze-frame data and related codes with a scan tool; note conditions when code set
Visually inspect sensor, harness, and connector for damage, corrosion, heat damage, or exhaust leaks near sensor
Backprobing: verify sensor supply, ground, heater power and control signals at connector
Use a manufacturer-capable scan tool or multimeter/oscilloscope to monitor pump current and sensor outputs
Check continuity and resistance of wiring between sensor and PCM; check for shorts to battery or ground
Verify fuel pressure, vacuum leaks and intake/exhaust condition if fuel trim is abnormal

Signal parameters

Pump current: measured by scan tool or oscilloscope as current value (µA or mA) — at stoichiometric conditions this should be near the sensor’s specified baseline (close to zero); deviations indicate lean/rich trim demand
Pump current will move positive or negative relative to baseline under rich/lean conditions—values and polarity are manufacturer specific, consult service manual
Heater circuit: supply voltage present with key on/crank; heater resistance per service spec (measure with connector disconnected)
Sensor response: pump current should change promptly with induced rich/lean events (response time specified by manufacturer)

Diagnostic algorithm

Record all DTCs and freeze-frame data; attempt to reproduce fault conditions with scan tool connected.
Visually inspect Bank 1 Sensor 1, connector, and harness for damage, corrosion, or signs of overheating; repair as needed.
Clear the code and perform a health check/drive cycle while monitoring pump current and O2/trims. Note whether code returns.
Verify power/ground to the sensor and heater circuit. Measure heater resistance and compare to spec. Repair any open/shorts.
Backprobe signal circuit and measure pump current with a capable scan tool or lab scope while inducing rich/lean conditions (throttle blips, propane enrichment) to confirm sensor activity.
Check wiring continuity between sensor and PCM for open, short to ground or battery, and high resistance; repair wiring or connector faults.
Inspect for exhaust leaks, intake vacuum leaks, faulty fuel pressure regulator or injectors that could cause abnormal pump current readings; correct if found.
If wiring and vehicle systems check good, replace the Bank 1 Sensor 1 with a known good/ OE-equivalent wideband sensor and retest.
If replacement sensor does not correct the issue, test or substitute the PCM or consult manufacturer technical service information for PCM driver tests and reprogramming requirements.
After repairs, clear codes and perform a full drive cycle to verify the code does not return and that fuel trims and emissions-related parameters are within spec.

Likely causes

Damaged or disconnected sensor wiring/connectors
Failed UEGO/pump-cell sensor at Bank 1 Sensor 1
Open or short in the sensor heater or reference circuits
Exhaust leak or sensor contaminated causing improper pump current

Fault status

⚠️ Status

P2626 — O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 1). Indicates pump-current circuit out of range or open; inspect sensor, wiring, heater, and PCM circuit.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours