Open or damaged wire in the pumping current trim circuit between the sensor and ECM.; Corroded or loose electrical connector at the Bank 2 Sensor 1 oxygen sensor.; Failed wideband oxygen sensor (Bank 2 Sensor 1) with an internal open circuit.; Faulty ECM driver for the pumping current trim circuit, though rare.; Physical damage to the sensor wiring harness from heat, chafing, or debris.; Poor ground connection affecting the sensor's reference circuit.

DTC codes / P26xx · Computer and output circuits / P2629

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

P2629 indicates that the engine control module (ECM) has detected an open circuit or abnormal condition in the trim circuit for the oxygen sensor pumping current on Bank 2 Sensor 1. This sensor is a wideband air-fuel ratio sensor that uses a pump cell to maintain a reference voltage, and the ECM monitors the current needed to do so; an open in that circuit prevents accurate fuel control.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Rough idle or unstable engine operation due to incorrect air-fuel ratio.
Reduced fuel economy as the ECM loses accurate feedback from the sensor.
Hesitation or stumble during acceleration when the engine is under load.
In some cases, the engine may enter limp mode or exhibit poor performance.
A slight increase in emissions may be observed during an emissions test.

Common causes, most likely first

Open or damaged wire in the pumping current trim circuit between the sensor and ECM.
Corroded or loose electrical connector at the Bank 2 Sensor 1 oxygen sensor.
Failed wideband oxygen sensor (Bank 2 Sensor 1) with an internal open circuit.
Faulty ECM driver for the pumping current trim circuit, though rare.
Physical damage to the sensor wiring harness from heat, chafing, or debris.
Poor ground connection affecting the sensor's reference circuit.

How to diagnose and fix it

Perform a visual inspection of the Bank 2 Sensor 1 wiring and connector for damage, corrosion, or loose pins.
Use a scan tool to check for other stored codes and freeze-frame data to confirm the fault conditions.
Measure resistance and continuity of the pumping current trim circuit between the sensor and ECM to identify an open.
Check the sensor's heater circuit and reference voltage to rule out other sensor faults.
If the circuit tests good, replace the Bank 2 Sensor 1 oxygen sensor with a quality direct-fit unit.
Clear codes and perform a road test to verify the repair and ensure the monitor runs to completion.
If the code persists after sensor replacement, diagnose the ECM and its connectors for internal faults.

Don't overlook the sensor connector

A common oversight is replacing the oxygen sensor when the real problem is a corroded connector or chafed wire that creates an intermittent open.
The pumping current trim circuit is sensitive to voltage drops, so a poor ground can mimic a faulty sensor and set this code.
This code can be set by a sensor that is contaminated with silicone or coolant, which alters its pumping current characteristics without a total failure.
On some vehicles, the ECM may set P2629 if the sensor's heater circuit fails, as the sensor cannot reach operating temperature and the pump current becomes erratic.
Always check for technical service bulletins (TSBs) for the specific vehicle, as some models have known harness routing issues that cause this code.

Can I keep driving with P2629?

You can usually drive the vehicle with this code, but expect reduced fuel economy and possibly poor engine performance; avoid heavy acceleration or towing until the fault is repaired to prevent potential catalytic converter damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.