What Is OBD Code P1168?
P1168 is a manufacturer-specific diagnostic trouble code (DTC) used exclusively by Nissan vehicles. It indicates that the engine control module (ECM) has detected a malfunction in the closed-loop fuel control function on Bank 2 of the engine. In a closed-loop fuel control system, the engine uses oxygen sensors to monitor exhaust gas composition and adjust the air-fuel mixture in real-time to maintain optimal combustion efficiency.
When the ECM detects that Bank 2 (the cylinder bank opposite the #1 cylinder) is not responding correctly to closed-loop fuel control commands, it sets this code. This is a Nissan-specific code, so you won’t see it on other vehicle manufacturers’ diagnostic systems.
What Does P1168 Mean?
The P1168 code breaks down as follows:
- P: Powertrain code (engine, transmission, or related systems)
- 1: Manufacturer-specific code (Nissan-defined)
- 168: Specific fault identifier for closed-loop control function on Bank 2
In technical terms, this code means the ECM is unable to maintain proper fuel trim on Bank 2. The fuel trim is the adjustment the ECM makes to the fuel injector pulse width to keep the air-fuel ratio at the target lambda value (typically 14.7:1 for gasoline engines). When the ECM cannot achieve this balance on Bank 2, it sets the P1168 code.
The closed-loop fuel control system relies on feedback from the oxygen sensor(s) on Bank 2. If this sensor is not providing accurate data, or if there’s an electrical problem in the circuit, the ECM cannot make proper fuel adjustments, triggering this code.
Common Symptoms
Drivers may experience the following symptoms when P1168 is present:
- Check Engine Light (CEL) illuminated on the dashboard
- Rough idle or engine hesitation during acceleration
- Decreased fuel economy
- Engine running lean or rich (noticeable by smell or performance)
- Difficulty starting the engine, especially in cold weather
- Misfires or rough running on Bank 2 cylinders
- Black smoke from the exhaust (rich condition)
- Reduced engine power or performance
- Possible rotten egg smell from the catalytic converter (if running too rich)
In some cases, the vehicle may run relatively normally despite the code being set, especially if the problem is intermittent or mild.
Possible Causes (Ranked by Frequency)
1. Faulty Bank 2 Oxygen Sensor
This is the most common cause of P1168. The oxygen sensor on Bank 2 may be failing, providing inaccurate voltage signals to the ECM. Over time, oxygen sensors degrade due to carbon buildup, heat exposure, and normal wear. A sensor that’s slow to respond or stuck at a fixed voltage will prevent proper closed-loop fuel control.
2. Oxygen Sensor Wiring or Connector Issues
Corroded, damaged, or loose wiring and connectors in the Bank 2 oxygen sensor circuit can cause poor electrical contact. This prevents the ECM from receiving accurate sensor signals. Common issues include:
- Corroded connector pins
- Damaged wiring harness
- Loose or disconnected connectors
- Water intrusion in the connector
3. Engine Control Module (ECM) Software or Hardware Issues
In rare cases, the ECM itself may have a software glitch or hardware failure that prevents it from processing Bank 2 oxygen sensor signals correctly. This is less common but can occur after software updates or due to electrical damage.
4. Fuel Injector Problems on Bank 2
A leaking, stuck, or malfunctioning fuel injector on Bank 2 can cause the air-fuel ratio to be incorrect, preventing proper closed-loop control. If the injector is stuck open, it will run rich; if stuck closed, it will run lean.
5. Exhaust Leaks
A leak in the exhaust manifold or exhaust system on Bank 2 can allow outside air to enter the exhaust stream before the oxygen sensor. This causes the sensor to read a lean condition even when the engine is running rich, confusing the ECM’s fuel control logic.
6. Air Intake Leaks
Vacuum leaks in the intake manifold or intake hoses on Bank 2 can cause the engine to run lean, making it difficult for the ECM to achieve proper closed-loop control.
7. Fuel Pressure Issues
Low or unstable fuel pressure can prevent the fuel injectors from delivering the correct amount of fuel, making it impossible for the ECM to maintain proper fuel trim on Bank 2.
Diagnostic Steps
Step 1: Verify the Code and Check for Additional Codes
Use an OBD-II scanner to confirm that P1168 is present. Note any other codes that may be stored. Related codes like P0130 (O2 Sensor Circuit), P0135 (O2 Sensor Heater), or other fuel trim codes can help pinpoint the issue.
Step 2: Perform a Visual Inspection
Inspect the Bank 2 oxygen sensor and its wiring for:
- Visible damage to the wiring harness
- Corroded or loose connectors
- The oxygen sensor itself (check for carbon buildup or damage)
- Exhaust leaks near the sensor
Step 3: Check Oxygen Sensor Voltage
Using a multimeter or scope, monitor the Bank 2 oxygen sensor voltage while the engine is running:
- Healthy sensor voltage should fluctuate between 0.1V and 0.9V at idle
- A stuck voltage (always high or always low) indicates a faulty sensor
- No voltage or erratic readings suggest wiring or connector issues
Step 4: Inspect the Oxygen Sensor Connector
Disconnect the Bank 2 oxygen sensor connector and inspect for:
- Corrosion on the pins
- Moisture or water inside the connector
- Bent or damaged pins
Clean the connector with electrical contact cleaner if corrosion is present. Reconnect and retest.
Step 5: Check for Exhaust Leaks
Inspect the exhaust manifold and piping on Bank 2 for cracks or loose connections. Use a smoke test if necessary to identify small leaks.
Step 6: Test Fuel Pressure and Fuel Injectors
Use a fuel pressure gauge to verify that fuel pressure is within the manufacturer’s specification (typically 40-60 PSI for most Nissan vehicles). Test individual fuel injectors on Bank 2 for proper operation using a fuel injector tester or oscilloscope.
Step 7: Check for Vacuum Leaks
Inspect all intake hoses and connections for cracks or loose fittings. Use a smoke test or propane enrichment test to identify vacuum leaks.
Step 8: Replace or Clean the Oxygen Sensor
If the sensor is faulty, replace it with a new OEM or quality aftermarket sensor. Some sensors can be cleaned if carbon buildup is the issue, but replacement is typically the most reliable solution.
Step 9: Clear the Code and Test Drive
After repairs, use the scanner to clear the P1168 code. Take the vehicle on a test drive to verify that the code does not return and that engine performance has improved.
Repair Cost Estimates
The cost to repair P1168 varies depending on the underlying cause:
- Oxygen Sensor Replacement: $150–$400 (parts and labor). OEM Nissan sensors are typically $100–$200, with labor around $50–$200 depending on sensor location and accessibility.
- Oxygen Sensor Connector/Wiring Repair: $50–$200. If only the connector or wiring needs repair or replacement, costs are minimal.
- Fuel Injector Replacement: $200–$600 per injector. If a fuel injector is faulty, replacement costs can be significant, especially if multiple injectors need service.
- Exhaust Manifold Repair/Replacement: $300–$1,000+. Exhaust leaks can be expensive to repair, especially if the manifold needs replacement.
- ECM Reprogramming or Replacement: $500–$1,500+. If the ECM is faulty, reprogramming or replacement may be necessary.
- Fuel Pressure Regulator Replacement: $200–$500. If fuel pressure issues are the cause, regulator replacement may be needed.
Most commonly, P1168 is resolved with an oxygen sensor replacement, making the typical repair cost $150–$400.
Can I Still Drive?
The severity of P1168 varies depending on the underlying cause and the vehicle’s condition:
Short-Term Driving (Safe)
In most cases, it is safe to drive the vehicle for short distances to a repair shop. The Check Engine Light will be on, but the engine will likely continue to run, albeit with reduced fuel economy and possibly rough idle.
Long-Term Driving (Not Recommended)
Driving with P1168 for extended periods is not recommended because:
- Fuel economy will suffer significantly
- Engine damage may occur if the engine is running too lean (lack of fuel) or too rich (excess fuel)
- The catalytic converter may be damaged by running too rich for extended periods
- Engine misfires could cause damage to internal engine components
When to Stop Driving Immediately
Stop driving and seek immediate repair if you experience:
- Severe engine misfires or hesitation
- Loss of power or inability to accelerate
- Overheating engine
- Rotten egg smell (indicating severe rich condition)
- Smoke from the engine or exhaust
Recommendation: Have the vehicle diagnosed and repaired within a few days to avoid potential engine damage and to restore fuel economy.
FAQ
Q: Is P1168 a serious code?
A: P1168 is moderately serious. While it typically doesn’t prevent the engine from running, it indicates a problem with fuel control that can lead to poor fuel economy, rough running, and potential engine damage if left unaddressed. Most P1168 issues can be resolved with an oxygen sensor replacement, which is a routine repair.
Q: Can I fix P1168 myself?
A: If you have mechanical experience, you can replace the Bank 2 oxygen sensor yourself. However, the sensor location varies by Nissan model, and some vehicles have sensors that are difficult to access. You’ll need an oxygen sensor socket and a basic understanding of electrical connectors. If the problem is related to wiring, connectors, or the ECM, professional diagnosis is recommended.
Q: Will P1168 go away on its own?
A: No, P1168 will not go away on its own. The code will remain stored in the ECM until the underlying problem is fixed and the code is cleared with a diagnostic scanner. Even if you clear the code without fixing the issue, it will return after a few drive cycles.
Q: What’s the difference between Bank 1 and Bank 2?
A: Bank 1 is the side of the engine that contains the #1 cylinder. Bank 2 is the opposite side. In a V6 or V8 engine, Bank 1 is typically the right side (driver’s side in most vehicles), and Bank 2 is the left side (passenger’s side). The P1168 code specifically refers to closed-loop control issues on Bank 2.
Q: How long do oxygen sensors last?
A: Most oxygen sensors last between 30,000 and 100,000 miles, depending on driving conditions and sensor quality. Sensors exposed to carbon buildup, extreme temperatures, or poor fuel quality may fail sooner. If your Nissan has high mileage and the oxygen sensor hasn’t been replaced recently, it’s a good candidate for replacement when P1168 appears.