Powertrain, generic (extended)

P2626 O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 1)

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

Wide-band lambda probes such as the Bosch LSU 4.9 carry a calibration resistor in their plug; the engine module uses it to scale the pumping current. P2626 says this trim path at the front probe of bank 1 looks open. Makers detect it differently: GM's 2023 tables let the sensor chip measure the resistor after each start and fail an LSU 4.9 above 379.5 ohms (NGK ZFAS-U2: above 4,644 ohms), type B. VW's 2014 data books flag a probe signal above 4.81 V, and the 2010 Saab 9-5 applies that limit during fuel cut-off (type B). Ford's Bosch-equipped engines run an air test in overrun and fail a pump current above 3.09 mA held for 2 s. Ford's TSB 17-2124 for the 3.5 L EcoBoost in Explorer and F-150 (2015-17) cures it with a new probe. Low and high faults are P2627/P2628; bank 2 is P2629.

Likely causes

Front wide-band probe defective (trim resistor, pump cell or heater damage)

Trim line broken or pin pushed back in the six-pin probe connector

Moisture or corrosion in the probe connector raising the measured resistance

Engine software requiring an update after probe replacement (some makes)

Symptoms

Check engine light
Fuel control falls back to open loop on bank 1
Slightly higher fuel consumption or rough idle

Repair estimate

DifficultyMediumDIY possible

Parts and labour€20–350

Time0.3–1.5 h

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

Parts involved

oxygen sensor bank1 sensor1sensor calibration resistoroxygen sensor wiring

References: gsi.ext.gm.com, static.nhtsa.gov, saabwisonline.com, fordservicecontent.com.