Code
P1168
NISSAN
P — Powertrain
Closed Loop Control Bank 2
Views:
UK: 44
EN: 63
RU: 36
AI status
Completed
Completed
100%
Causes
- Faulty or slow upstream oxygen sensor (Bank 2)
- Open or shorted O2 sensor wiring or poor connector/ground
- Heater circuit failure on Bank 2 oxygen sensor
- Exhaust leak near upstream sensor on Bank 2
- Fuel delivery problem (low/high fuel pressure) affecting Bank 2
- Intake vacuum leak or air leak on Bank 2 intake runners
Symptoms
- MIL (Check Engine Light) illuminated
- Reduced fuel economy
- Rough idle or hesitation under load
- Failed emissions/inspections (high HC/CO/NOx)
- Elevated short‑term or long‑term fuel trims for Bank 2
- Black smoke (if persistently rich) or lean surge/hesitation (if lean)
What to check
- Read freeze frame and pending/confirmed codes with a scan tool; record live data for O2 sensors and fuel trims
- Monitor Bank 2 upstream oxygen sensor voltage and heater status while engine is warmed up
- Compare Bank 1 vs Bank 2 O2 sensor behavior and fuel trims (STFT/LTFT)
- Inspect wiring, connectors and grounds for the Bank 2 O2 sensor and heater circuit
- Visually check for exhaust leaks near the Bank 2 upstream sensor flange/collector
- Perform a fuel pressure test to verify system pressure and regulator operation
Signal parameters
- Upstream O2 sensor (heated): switching ~0.1–0.9 V when warmed and cycling in closed loop
- Heater resistance typically
- Short‑term fuel trim (STFT) normally within ±10% (manufacturer range may vary)
- Long‑term fuel trim (LTFT) generally within ±10% (values beyond ±20% indicate larger issue)
- O2 sensor switching frequency >1 Hz at warm idle indicates healthy response (slow or fixed voltage indicates problem)
- Fuel rail pressure should match manufacturer specification (see service manual)
Diagnostic algorithm
- Connect a capable scan tool and confirm P1168 and any related codes; record freeze frame data
- Warm engine to normal operating temperature; observe Bank 2 upstream O2 sensor voltage waveform and heater status in live data
- If the O2 sensor shows fixed or very slow voltage, test heater circuit for continuity and power/ground with key on; verify heater draws current when commanded
- Perform a wiggle test and inspect the harness/connectors for corrosion or damage; repair any wiring issues
- Check for exhaust leaks upstream of the sensor; repair any leaks and retest
- Perform a smoke test to find intake vacuum leaks on the Bank 2 side; repair leaks and retest
- Measure fuel pressure and compare to spec; repair fuel pump/regulator or injectors if pressure is incorrect
- If O2 sensor wiring and fuel/air systems are good but the PCM still will not enter closed loop, consider replacing the upstream Bank 2 O2 sensor and retest
- After repairs, erase codes and perform a drive cycle to confirm closed‑loop operation is achieved and P1168 does not return; if it does, escalate to PCM/software diagnostics
Likely causes
- Failed or slow switching Bank 2 upstream O2 sensor
- Damaged wiring or poor connector at Bank 2 oxygen sensor
- Exhaust leak upstream of the Bank 2 sensor
- Fuel pressure out of specification causing persistent rich/lean condition
Fault status
Status
Closed Loop Control Bank 2 — PCM not operating Bank 2 in closed‑loop (O2 feedback)
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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