P2251 code meaning
O2 Sensor Negative Current Control Circuit/Open (Bank 1 Sensor 1)
Powertrain system Generic code P22xx codes Check engine light
What P2251 means
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.
P2251 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2251
- Check engine light
- Higher fuel consumption from open-loop fuelling on bank 1
- Possible rough running or failed emissions test
Common causes of P2251
- Most likelyBroken reference ground wire or pushed-back pin between sensor and ECM
- PossibleInternal open circuit in the wide-band sensor
- Less likelyEngine software that sets the code falsely (reprogramming for some models)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Oxygen sensor bank1 sensor1Oxygen sensor wiringECM
What each part of P2251 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 2 | Area: fuel and air metering (injector circuit). |
| 51 | The exact fault in that area. |
What to do next
- Note P2251 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2251
What does P2251 mean?
P2251 means "O2 Sensor Negative Current Control Circuit/Open (Bank 1 Sensor 1)". P2251 points to an open negative current control line, i.e. It is a generic code, so it means the same on every make.
Is it safe to drive with P2251?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2251 fail an emissions test?
Yes, it can. P2251 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2251 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P2251 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.