P2251: O2 Sensor Negative Current Control Circuit/Open (Bank 1 Sensor 1)

P2251 points to an open negative current control line, i.e. the reference or virtual ground (VM on Bosch, COM on NTK) of the bank 1 upstream wide-band sensor. Ford detects it on Bosch parts by a sensor voltage stuck in a narrow band, or by a reference-current pulse that still moves lambda; NTK chips report the break directly. GM's 2005 V6 and Saab's 2010 9-5 look for 1.47-1.53 V with cell resistance above 570 ohms and exhaust below 900 °C (Type B); VW's 2014 Passat book uses a 950-ohm limit. GM calls it low reference circuit. Bulletins: ECM reflash for the 2020-22 Corvette (22-NA-019) and 2013-14 Dart 2.4 (18-011-14), new sensor for 2016-18 Range Rover TDV6 (LTB01191) and 2025 Wrangler (23-019-25). P2254 is bank 2, P2252/P2253 low/high.

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
• Higher fuel consumption from open-loop fuelling on bank 1
• Possible rough running or failed emissions test

Most likely causes

• Broken reference ground wire or pushed-back pin between sensor and ECM
• Internal open circuit in the wide-band sensor
• Engine software that sets the code falsely (reprogramming for some models)

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 continuity of the wire between the component and the control module.
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 P2251 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• 51: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2251?

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 P2251?

The most common causes are: broken reference ground wire or pushed-back pin between sensor and ECM; internal open circuit in the wide-band sensor; engine software that sets the code falsely (reprogramming for some models).

Related codes

• P2252O2 Sensor Negative Current Control Circuit Low (Bank 1 Sensor 1)
• P2253O2 Sensor Negative Current Control Circuit High (Bank 1 Sensor 1)
• P2254O2 Sensor Negative Current Control Circuit/Open (Bank 2 Sensor 1)
• P2243O2 Sensor Reference Voltage Circuit/Open (Bank 1 Sensor 1)
• P2237O2 Sensor Positive Current Control Circuit/Open (Bank 1 Sensor 1)
• P0130O2 Sensor Circuit Bank 1 Sensor 1

Sources

• newtonnet.co.uk: fordobd2012
• gsi.ext.gm.com: 2005file14
• saabwisonline.com: dtc p2237 p2239 p2243 p2251 or p2626
• static.nhtsa.gov: MC 10074004 2280

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.