OBD-II code family
Oxygen Sensor Negative-Current Control Faults (6 codes)
6 related fault descriptions. Use each full code and the exact vehicle service information to identify its circuit, monitored condition, and required tests.
Codes in this family
This is the complete published member list for this guide. Each code retains its own page; shared diagnostic context does not mean that every member has the same test or repair.
- P2251O2 Sensor Negative Current Control Circuit/Open (Bank 1 Sensor 1)
- 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)
- P2255O2 Sensor Negative Current Control Circuit Low (Bank 2 Sensor 1)
- P2256O2 Sensor Negative Current Control Circuit High (Bank 2 Sensor 1)
What these codes mean
These six entries retain two sensor addresses and three reported conditions. P2251 is the negative-current control circuit/open category for Bank 1 Sensor 1; P2252/P2253 retain its low/high conditions. P2254 is circuit/open for Bank 2 Sensor 1, with P2255/P2256 low/high on that address. The complete vehicle code and reporting module determine the actual monitor and circuit assignment.
Negative-current is a circuit designation, not a direct measurement proving lean exhaust or a universal name for a chassis-ground wire. Bosch’s LSU 4.9 component example separately identifies pump-current, virtual-ground, heater and Nernst connections. Its connector calibration is a feature of that design, not proof that every vehicle or replacement sensor uses the same connections, resistor or controller interpretation.
Manufacturer examples make the electrical meaning concrete. Ford’s July 2024 summary distinguishes Bosch CJ125/ATIC42 RE/VM open and response-monitor logic from NTK IP/VS/COM circuit mapping; its P2251/P2254 paths must be interpreted in those stated configurations. A lack of signal movement cannot be converted into a universal resistance or unplug-and-replace rule.
The Mitsubishi 2022 NS22 P2251 entry concerns a linear air-fuel-ratio sensor open/impedance monitor, but the same manual’s P2252/P2253 entries concern rear heated-oxygen-sensor offset voltage. Its high-offset procedure checks more than one conductor for a short to power. These cases must not be collapsed into a universal front-sensor return-to-chassis explanation or high-means-only-resistance diagnosis.
The cited Toyota 2AZ-FE SFI excerpt identifies P2252/P2253 as reference-ground AF- circuit low/high and separates those paths from the pumping-current circuit. GM’s 2005 3.5L L66 parameters identify Bank 2 P2255 in a sensor-cell short check and P2256 in a sensor-cell open check. These bounded examples do not transfer one vehicle’s terminals, thresholds or service sequence to another.
Save the full scan, suffixes, status and recorded conditions, together with recent sensor or exhaust work. Verify the fitted application and any disturbed connections. A clear companion bank or normal fuel-trim snapshot does not prove that supplies, references or controller paths are independent or healthy; another bank’s code needs diagnosis rather than an automatic shared-ground conclusion.
Have a qualified technician match the component and use the prescribed protected circuit, connector and sensor checks. Do not ground an unidentified reference, bridge terminals, apply heater power, force a mixture change or combine connected probes with road driving as a generic check. A matched professional procedure and its safeguards belong with the technician, not an improvised owner test.
Repair the demonstrated fault and complete the prescribed verification. A sensor, harness, connector or controller decision requires its own evidence; a circuit label does not justify paired parts replacement or a catalyst repair. Seek a vehicle-specific estimate after diagnosis and follow actual warnings and recovery instructions if running is impaired. These code names cannot guarantee a particular fallback or safe travel distance.
Identify the circuit on your vehicle
Match the full DTC, reporting module, and any failure-type suffix to the service information for your exact year, make, model, engine, and equipment. An identifier alone does not establish installed hardware count, location, connector pinout, or a universal measurement.
Where the manufacturer publishes its own meaning for this code, that is the one to work from — it describes the actual component on your vehicle, which the generic definition cannot. Keep the generic description for what it is good for: it tells you which subject area the standard assigned the code to, which is useful context when the two appear to disagree. If they do disagree, follow the manufacturer.