P2255

Code

Generic P — Powertrain

O2 Sensor Negative Current Control Circuit Low Bank 2 Sensor 1

Brand: Generic

Type: P — Powertrain

Views: UK: 28 EN: 78 RU: 30

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Page language: EN

Causes

Faulty Bank 2 Sensor 1 oxygen sensor (internal short, contamination or failure)
Open, short to ground, short to voltage or high resistance in the sensor negative-current/control wiring or connectors
Corroded or loose sensor connector or poor ground
Exhaust leak near the sensor or sensor contaminated by coolant/oil
Defective or failed PCM (rare)
Incorrect replacement sensor (incompatible type/wiring)

Symptoms

Check Engine MIL illuminated
Poor fuel economy or running rich/lean under some conditions
Failed emissions test
Rough idle, hesitation or reduced engine performance in some cases
Possible downstream fuel trim abnormalities and drivability issues

What to check

Read and record freeze frame and all active/previous oxygen sensor DTCs with a scan tool
Visually inspect Bank 2 Sensor 1 harness, connector and pins for corrosion, damage, or heat damage
Check for exhaust leaks upstream of the sensor that can affect readings
Monitor live data for Bank 2 Sensor 1 (voltage/current/controlled current) with a capable scan tool or scope
Verify sensor heater operation (where applicable) and fuse/relay powering the heater circuit
Measure resistance and backprobe the sensor control circuit for opens/shorts to ground or battery

Signal parameters

Narrowband O2 (if used): typical output ~0.1–0.9 V, switching frequently when warmed; values outside this range or stuck may indicate a problem
Wideband/UEGO (if used): controller uses current control rather than simple voltage — expected commanded current usually centers near zero at stoichiometric and will vary positive/negative according to air/fuel; consult OEM service data for exact current ranges
Heater circuit: typically powered on key-on/run; verify heater voltage present and heater resistance per service data
Target/current-control values and thresholds are manufacturer-specific — confirm with OEM diagnostics before concluding failure

Diagnostic algorithm

Retrieve all related DTCs and freeze-frame data. Confirm P2255 is current and note conditions (engine temp, load, RPM).
Perform a visual inspection of the Bank 2 Sensor 1 harness and connector. Repair any damaged insulation, pins, or connectors.
With key on engine off, check sensor connector for proper battery/ground presence on heater circuit (if applicable) and measure resistance of heater against service spec.
Backprobe the sensor signal/control circuit and observe live data with a scan tool. For wideband sensors monitor commanded current/actual feedback where available.
Check for wiring shorts: measure continuity from the sensor control conductor to ground and to battery; verify there is no short to ground or supply when not commanded.
Wiggle test harness while observing live data to find intermittent opens/shorts.
If wiring and connector are good, swap with a known-good identical sensor (if available) or replace Bank 2 Sensor 1 and clear codes. Retest drive until warm and verify no return of the code.
If code returns after sensor replacement and wiring checks, perform PCM circuit tests per manufacturer service manual. Replace PCM only after ruling out sensor/harness issues.
After repairs clear codes and perform a drive cycle / verify readiness and emissions parameters.

Likely causes

Damaged sensor harness (chafing, pinched, exposed conductors) causing short to ground
Corroded/loose pin or connector at the sensor
Failed wideband/UEGO upstream sensor element or amplifier
Sensor contaminated by oil/coolant or physically damaged by exhaust heat
Aftermarket/incorrect sensor with different signal/current characteristics

Fault status

⚠️ Status

P2255: O2 Sensor Negative Current Control Circuit Low — PCM detected abnormally low negative-current control signal from bank 2 sensor 1. Check sensor, wiring/connectors, and PCM control circuit.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

Repair manuals