The P1168 trouble code is a diagnostic code that indicates a problem with the fuel system or engine management in certain vehicles. This code specifically relates to the closed loop control function for bank 2 of the engine, which means the engine control module (ECM) is detecting an issue with the air-fuel mixture on one side of the engine. Understanding and resolving this code is crucial for maintaining optimal engine performance and preventing potential damage.
| P1168 Code Meaning | P1168 Code Common Causes |
|---|---|
| Closed loop control – bank 2 – inoperative | Faulty oxygen (O2) sensor |
| Fuel rail pressure sensor in range but low | Damaged wiring or connectors |
| Air-fuel mixture imbalance in bank 2 cylinders | Exhaust leaks |
| ECM unable to maintain proper fuel trim | Faulty fuel pressure regulator |
| Potential fuel delivery system malfunction | Clogged or failing fuel injectors |
Understanding Closed Loop Control and Bank 2
Before diving into the specifics of the P1168 code, it’s essential to understand what closed loop control and bank 2 mean in the context of engine operation.
Closed Loop Control
Closed loop control refers to the engine management system’s ability to adjust the air-fuel mixture based on feedback from oxygen sensors. When an engine is in closed loop operation, it means:
- The engine has reached normal operating temperature
- The oxygen sensors are providing accurate readings
- The ECM is actively adjusting fuel injection based on these readings
In contrast, open loop operation occurs during cold starts or when the oxygen sensors are not yet warm enough to provide accurate readings. During open loop, the ECM relies on pre-programmed fuel maps rather than real-time sensor data.
Bank 2 Identification
In engines with two cylinder banks (typically V6 or V8 configurations), bank 2 refers to the group of cylinders opposite to bank 1. Bank 1 always contains cylinder number 1. For most vehicles:
- In transverse-mounted engines, bank 1 is typically the side closest to the firewall
- In longitudinally-mounted engines, bank 1 is usually the passenger side in left-hand drive vehicles
Identifying bank 2 is crucial for diagnosing and resolving the P1168 code, as it narrows down the area of concern within the engine.
Symptoms of P1168 Code
When a vehicle triggers the P1168 code, several symptoms may be noticeable:
- Illuminated check engine light
- Reduced fuel efficiency
- Rough idle or engine hesitation
- Decreased engine performance
- Difficulty starting the engine
- Increased emissions
It’s important to note that some vehicles may not exhibit noticeable symptoms beyond the check engine light. However, addressing the issue promptly is crucial to prevent potential long-term damage to the engine or catalytic converter.
Diagnosing P1168 Code
Proper diagnosis of the P1168 code requires a systematic approach. Follow these steps to identify the root cause:
- Verify the code: – Use an OBD-II scanner to confirm the P1168 code – Check for any additional codes that may be related
- Inspect the oxygen sensor: – Locate the bank 2 sensor 1 (upstream) oxygen sensor – Check for physical damage or contamination – Examine the wiring and connectors for signs of wear or corrosion
- Test the oxygen sensor: – Use a digital multimeter to check the sensor’s voltage output – Typical voltage range should fluctuate between 0.1V and 0.9V – A steady voltage may indicate a faulty sensor
- Check for exhaust leaks: – Inspect the exhaust manifold and pipes for cracks or loose connections – Listen for unusual exhaust noises that may indicate a leak
- Examine the fuel system: – Check fuel pressure using a fuel pressure gauge – Inspect fuel injectors for clogging or leaks – Test the fuel pressure regulator for proper operation
- Analyze fuel trim data: – Use an advanced scan tool to view short-term and long-term fuel trim values – Look for significant deviations from normal ranges (typically ±10%)
- Perform a smoke test: – Use a smoke machine to detect any vacuum leaks in the intake system – Pay close attention to hoses, gaskets, and the throttle body
- Check the mass airflow sensor: – Inspect the sensor for contamination – Test the sensor’s output using a multimeter or scan tool
Solutions for P1168 Code
Once the root cause has been identified, consider the following solutions:
Oxygen Sensor Replacement
If the oxygen sensor is faulty, replacement is often the best solution. To replace the sensor:
- Locate the bank 2 sensor 1 oxygen sensor
- Disconnect the electrical connector
- Remove the sensor using an oxygen sensor socket
- Install the new sensor, ensuring proper torque
- Reconnect the electrical connector
- Clear the code and test drive the vehicle
Cost estimate: $50 to $200 for the sensor, plus labor if not DIY
Warning: Always use an oxygen sensor specific to your vehicle make and model to ensure proper fitment and function.
Wiring Repair
If damaged wiring or connectors are found:
- Identify the damaged section
- Cut out the damaged portion
- Use appropriate gauge wire for splicing
- Solder the connections and use heat shrink tubing for insulation
- Secure the repaired wiring with zip ties or electrical tape
Cost estimate: $20 to $100 for materials, plus labor if not DIY
Recommendation: If extensive wiring damage is found, consider replacing the entire wiring harness for that section.
Exhaust Leak Repair
To fix an exhaust leak:
- Locate the source of the leak
- For small cracks, use high-temperature exhaust tape or sealant
- For larger holes or severely damaged sections, replace the affected part
- Ensure all connections are tight and properly sealed
Cost estimate: $10 to $500, depending on the severity and location of the leak
Warning: Always work on a cool exhaust system to avoid burns.
Fuel System Maintenance
To address fuel system issues:
- Replace the fuel filter if clogged
- Clean or replace fuel injectors if necessary
- Test and replace the fuel pressure regulator if faulty
- Inspect and clean the mass airflow sensor
Cost estimate: $50 to $500, depending on the components needing attention
Recommendation: Use quality fuel system cleaners periodically to maintain injector and sensor performance.
ECM Reprogramming
In some cases, especially with certain Nissan models, reprogramming the ECM may resolve the P1168 code:
- Consult with a dealership or specialized automotive programmer
- Ensure the latest software version is installed
- Clear all codes and perform a test drive
Cost estimate: $100 to $300 for reprogramming service
Warning: ECM reprogramming should only be performed by qualified professionals with the proper equipment.
Preventing Future P1168 Codes
To minimize the risk of encountering the P1168 code in the future:
- Use high-quality fuel and consider periodic fuel system cleaning
- Follow the manufacturer’s recommended maintenance schedule
- Address check engine lights promptly to prevent cascading issues
- Regularly inspect and replace wear items like spark plugs and air filters
- Avoid extended periods of vehicle inactivity, which can lead to fuel degradation
When to Seek Professional Help
While many aspects of diagnosing and resolving the P1168 code can be handled by experienced DIY mechanics, there are situations where professional assistance is recommended:
- If you lack the necessary diagnostic tools or expertise
- When multiple related codes are present, indicating a more complex issue
- If the problem persists after attempting the solutions outlined above
- When dealing with newer vehicles with complex engine management systems
Professional mechanics have access to advanced diagnostic equipment and manufacturer-specific information that can expedite the troubleshooting process.
Frequently Asked Questions About P1168
- Can I drive my vehicle with the P1168 code?
While the vehicle may still operate, it’s not recommended to drive long distances with this code present. Continued operation could lead to catalytic converter damage or decreased fuel efficiency. - How much does it typically cost to fix a P1168 code?
Costs can vary widely, from $50 for a simple oxygen sensor replacement to $500 or more for complex fuel system repairs. The exact cost depends on the root cause and whether professional labor is required. - Will the P1168 code clear itself?
In some cases, the code may clear if the issue was temporary. However, if the underlying problem persists, the code will likely return. - Is the P1168 code specific to certain vehicle makes?
While P1168 can appear in various vehicles, it’s commonly associated with Nissan models. Always consult your vehicle’s specific diagnostic information for accurate interpretation. - How long does it take to diagnose and fix a P1168 code?
Diagnosis can take 1-2 hours, while repairs may range from 30 minutes for a simple sensor replacement to several hours for more complex fuel system issues. - Can a bad catalytic converter cause a P1168 code?
While not a direct cause, a failing catalytic converter can affect exhaust flow and oxygen sensor readings, potentially contributing to a P1168 code. - Is it safe to use fuel additives to address a P1168 code?
Quality fuel system cleaners may help if the issue is related to carbon buildup or minor injector clogging. However, they are not a guaranteed fix for all P1168-related problems. - How often should oxygen sensors be replaced to prevent P1168 codes?
Most oxygen sensors last between 60,000 to 100,000 miles. Regular inspection and replacement at recommended intervals can help prevent P1168 and other oxygen sensor-related codes.
In conclusion, the P1168 code, while potentially concerning, is often resolvable with proper diagnosis and targeted repairs. By understanding the code’s meaning, common causes, and appropriate solutions, vehicle owners and DIY mechanics can approach this issue with confidence. Remember to always prioritize safety and seek professional help when needed to ensure your vehicle remains in optimal condition.