P2628: O2 Sensor Pumping Current Trim Circuit High (Bank 1 Sensor 1)

With P2628 the trim input of the front wide-band probe on bank 1 lies above its permitted range. Ford's 2020-23 petrol summary reserves it for NTK probes, where the interface chip reports the resistor line shorted to battery voltage. In GM's 2005 table for the Honda-sourced 3.5 L V6 it is the opposite end of P2627: the label resistor voltage drops under 0.29 V for 5 s. GM diesels apply it to the NOx sensor oxygen value downstream of the turbine; the 2020 table counts readings above 27 percent, i.e. more oxygen than air, in 100 of 200 samples and only while exhaust pressure is plausible (type B). A trim value out of range skews the lambda value the probe reports, so the module stops trusting the probe. Low is P2627, open P2626, bank 2 high P2631.

Bank 1 is the side of the engine with cylinder 1. Inline engines only have this bank. Sensor 1 is the oxygen sensor before the catalytic converter.

Symptoms

• Check engine light
• Mixture control without probe feedback, higher consumption
• On diesels NOx-related codes and possible SCR warnings

Most likely causes

• Trim line shorted to battery or another supply in the harness or plug
• Wide-band probe or NOx sensor delivering an implausible value
• Exhaust leak ahead of the sensor drawing in outside air

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the wiring and connector of the sensor indicated
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Look for exhaust leaks
4. Check the signal in live data with the engine warm
5. Check the fuse and the heater resistance if the code mentions it
6. Replace the sensor if it has power and does not respond

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2628 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 6: Control modules and outputs
• 28: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2628?

Yes, you can normally drive in moderation, but get it repaired soon: you will use more fuel and the catalytic converter can be damaged over time.

What causes code P2628?

The most common causes are: trim line shorted to battery or another supply in the harness or plug; wide-band probe or NOx sensor delivering an implausible value; exhaust leak ahead of the sensor drawing in outside air.

Related codes

• P2626O2 Sensor Pumping Current Trim Circuit/Open (Bank 1 Sensor 1)
• P2627O2 Sensor Pumping Current Trim Circuit Low (Bank 1 Sensor 1)
• P2631O2 Sensor Pumping Current Trim Circuit High (Bank 2 Sensor 1)
• P2237O2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)
• P0132O2 Sensor Circuit High Voltage Bank 1 Sensor 1

Sources

• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• gsi.ext.gm.com: 2005file13
• gsi.ext.gm.com: 20OBDG04 Diagnostics
• bosch-motorsport.com: Data Sheet 69034379 Lambda Sensor LSU 4.9

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.