Code
P1168
INFINITI
P — Powertrain
HO2S11 Label Circuit Low Voltage Fault Bank 1 Sensor 1
AI status
Completed
Completed
100%
Causes
- Damaged or shorted O2 sensor signal wire (short to ground)
- Poor or corroded connector or pin at the sensor or PCM
- Failed or degraded HO2S (internal heater or sensing element)
- Open or high-resistance ground or reference circuit
- Low fuel pressure, vacuum leak, or other condition causing very lean mixtures
- PCM or wiring harness damage (chafing, water intrusion)
Symptoms
- Check Engine Light (MIL) illuminated
- Poor fuel economy or rough idle if fuel trims are affected
- Hesitation, stumble, or reduced drivability under some conditions
- Failure to pass emissions test due to upstream sensor fault
- Long-term fuel trim corrections (lean) visible in live data
What to check
- Read freeze frame and live data with a scan tool: monitor B1S1 voltage and short/long term fuel trim (STFT/LTFT)
- Visually inspect sensor, connector, and harness for damage, corrosion, or water intrusion
- Back-probe the sensor signal wire and measure voltage while engine is at operating temperature in closed loop
- Check heater circuit: measure resistance of heater element and verify 12V supply and ground when key on/engine running
- Perform wiggle test on harness while watching live data for intermittent changes
- Check for intake leaks, fuel pressure issues, or other conditions causing lean operation
Signal parameters
- Normal HO2S (upstream B1S1) switching: approx. 0.1 V (lean) to 0.9 V (rich) in closed-loop, rapidly switching
- A persistent low-voltage fault: signal below ~0.1–0.2 V or stuck low compared to expected switching
- Heater resistance (typical range, model-dependent): roughly 2–20 ohms (consult vehicle service data for exact value)
- Heater supply: battery voltage (~10–14 V) present to heater circuit when key on/engine running
- No short to ground on signal wire — should float between ~0.1–0.9 V, not pulled to 0 V
Diagnostic algorithm
- Retrieve and record freeze frame and live data (B1S1 voltage, short & long term fuel trims, engine temp, fuel trims).
- Confirm code is current: clear codes and road test to see if P1168 returns while monitoring B1S1.
- Visually inspect sensor, connector, and harness for corrosion, damage, or water intrusion; repair as needed.
- With engine warmed and in closed loop, back-probe the B1S1 signal wire and observe voltage. If signal is stuck low (
- Unplug sensor and check signal circuit for short to ground using an ohmmeter between signal wire and chassis ground; there should not be a direct short. Also check for short to 12V.
- Check sensor ground and reference circuits for continuity to PCM ground and proper resistance; repair poor grounds.
- Measure heater element resistance at the sensor connector (compare to factory spec). With key ON, check for heater supply voltage at the connector; if heater supply/ground missing, trace power feed and fuses/relays.
- If wiring checks OK and heater/power are good but signal is still invalid, substitute a known-good upstream O2 sensor and re-test to confirm cure before replacing ECM.
- If new sensor cures the complaint, re-install properly. If code persists with known-good sensor and verified wiring, suspect PCM or intermittent wiring harness faults and escalate to module-level diagnosis.
Likely causes
- Wiring short to ground on HO2S Bank1 Sensor1 signal
- Corroded/loose sensor connector or terminal
- Failed upstream oxygen sensor
- Open/heavily corroded ground or reference circuit to sensor
- Intake vacuum leak causing persistent lean condition
Fault status
Status
HO2S Bank 1 Sensor 1 Circuit Low Voltage (P1168) — check sensor signal, wiring, heater circuit, and grounds.
Repair difficulty: Medium
Diagnostic time: 1.5 - 3 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email