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

What the P2626 code means

Wideband sensors, also called A/F sensors, measure the mixture accurately across the whole range, not just whether it is rich or lean. They have a pumping cell and a reference cell, and the computer controls the pumping current to measure the oxygen.

The sensor gets a 5 V reference and a ground from the computer and returns a signal between roughly 0.5 and 4.5 V. A high signal, like the one behind the P2626 code, usually comes from an open circuit or an interrupted ground.

These sensors have five or six wires and are not tested like classic oxygen sensors: the scan tool shows a lambda ratio or a current in milliamps.

To confirm it, measure the continuity of each wire between the component connector and the computer connector with the key off. It should be under 1 ohm, and an infinite reading means that wire is open. If the wiring is good, measure the component itself: an infinite resistance confirms it is open inside.

P2626 code symptoms

• Check engine light on.
• The mixture stays at fixed values, fuel use goes up and the engine may run worse.

Likely causes of the P2626 code

1. Loose or broken connector. The most frequent cause.
2. Signal or ground wire cut, so the signal climbs up to the reference voltage.
3. Sensor open inside, with infinite resistance.
4. Short to 5 V or 12 V from rubbing against another wire in the harness.

How to diagnose the P2626 code step by step

1. Read the sensor value on the scan tool and compare it with what you expect.
2. Inspect the connector for corrosion, water or loose pins.
3. Check supply and ground with the key on: the reference should be correct and the ground voltage drop should be under 0.1 V.
4. Measure the signal with the connector plugged in and see whether it changes with the operating condition.
5. Do a wiggle test on the harness with the scan tool in graph mode.
6. Check continuity of each wire to the computer, which should be under 1 ohm.

How to fix the P2626 code

• Repair the connector or the wiring.
• Replace the sensor if the tests confirm it is bad.
• Correct the real condition if there is one.
• Clear the codes and verify with a road test.

Technical reference data

• Lambda 1.00 is the ideal mixture. Above 1 is lean. Below 1 is rich.
• Pumping current: near 0 mA at lambda 1, positive when lean and negative when rich.
• Heater: typical resistance of 2 to 5 ohms when cold.
• Approximate values only: check the manufacturer data for your vehicle.

Brand-specific notes

Check the connector before you buy a wideband sensor, because they are expensive. A loose or corroded plug is the most common reason for an open circuit, and it explains the P2626 code more often than the sensor itself.

P2626 on Toyota, Lexus, Honda, Subaru, Volkswagen and BMW

Common on these makes, which use wideband sensors ahead of the catalytic converter.

Frequently asked questions about P2626